Re: [PATCH 1/2] dmaengine: add msm bam dma driver

[Stephen Boyd]

On 10/25, Andy Gross wrote:
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index f238cfd..a71b415 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -364,4 +364,13 @@ config DMATEST
>  	  Simple DMA test client. Say N unless you're debugging a
>  	  DMA Device driver.
>  
> +
> +config MSM_BAM_DMA
> +	tristate "MSM BAM DMA support"
> +	depends on ARCH_MSM

It would be nice if we didn't have to rely on ARCH_MSM here so we
get more build coverage.

> +	select DMA_ENGINE
> +	---help---
> +	  Enable support for the MSM BAM DMA controller.  This controller
> +	  provides DMA capabilities for a variety of on-chip devices.
> +
>  endif
> diff --git a/drivers/dma/msm_bam_dma.c b/drivers/dma/msm_bam_dma.c
> new file mode 100644
> index 0000000..d16bf94
> --- /dev/null
> +++ b/drivers/dma/msm_bam_dma.c
> @@ -0,0 +1,840 @@
> +/*
> + * MSM BAM DMA engine driver
> + *
> + * Copyright (c) 2013, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/dmaengine.h>
> +#include <linux/interrupt.h>

interrupt.h is here twice

> +#include <linux/scatterlist.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_dma.h>
> +#include <linux/clk.h>
> +#include <linux/msm_bam_dma.h>
> +
> +#include "dmaengine.h"
> +#include "msm_bam_dma_priv.h"

Why do we need this file? Can't we just put the #defines in this
file?

> +
> +
> +/*

There should be two '*'s here for kernel-doc.

> + * bam_alloc_chan - Allocate channel resources for DMA channel.
> + * @chan: specified channel
> + *
> + * This function allocates the FIFO descriptor memory and resets the channel
> + */
> +static int bam_alloc_chan(struct dma_chan *chan)
> +{
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +	struct bam_device *bdev = bchan->device;
> +	u32 val;
> +	union bam_pipe_ctrl pctrl;
> +
> +	/* check for channel activity */
> +	pctrl.value = ioread32(bdev->regs + BAM_P_CTRL(bchan->id));

I recall io{read,write}*() being used for PCI and other ioport
devices. If that's right then readl/writel would be more
appropriate, and the *_relaxed variants would be even better if
the correct memory barriers are also put in place.

> +	if (pctrl.bits.p_en) {
> +		dev_err(bdev->dev, "channel already active\n");
> +		return -EINVAL;
> +	}
> +
> +	/* allocate FIFO descriptor space */
> +	bchan->fifo_virt = (struct bam_desc_hw *)dma_alloc_coherent(bdev->dev,

There isn't any need to cast from void *.

> +				BAM_DESC_FIFO_SIZE, &bchan->fifo_phys,
> +				GFP_KERNEL);
> +
> +	if (!bchan->fifo_virt) {
> +		dev_err(bdev->dev, "Failed to allocate descriptor fifo\n");
> +		return -ENOMEM;
> +	}
> +
> +	/* reset channel */
> +	iowrite32(1, bdev->regs + BAM_P_RST(bchan->id));
> +	iowrite32(0, bdev->regs + BAM_P_RST(bchan->id));
> +
> +	/* configure fifo address/size in bam channel registers */
> +	iowrite32(bchan->fifo_phys, bdev->regs +
> +			BAM_P_DESC_FIFO_ADDR(bchan->id));
> +	iowrite32(BAM_DESC_FIFO_SIZE, bdev->regs +
> +			BAM_P_FIFO_SIZES(bchan->id));
> +
> +	/* unmask and enable interrupts for defined EE, bam and error irqs */
> +	iowrite32(BAM_IRQ_MSK, bdev->regs + BAM_IRQ_SRCS_EE(bchan->ee));
> +
> +	/* enable the per pipe interrupts, enable EOT and INT irqs */
> +	iowrite32(P_DEFAULT_IRQS_EN, bdev->regs + BAM_P_IRQ_EN(bchan->id));
> +
> +	/* unmask the specific pipe and EE combo */
> +	val = ioread32(bdev->regs + BAM_IRQ_SRCS_MSK_EE(bchan->ee));
> +	val |= 1 << bchan->id;
> +	iowrite32(val, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bchan->ee));
> +
> +	/* set fixed direction and mode, then enable channel */
> +	pctrl.value = 0;
> +	pctrl.bits.p_direction =
> +		(bchan->bam_slave.slave.direction == DMA_DEV_TO_MEM) ?
> +			BAM_PIPE_PRODUCER : BAM_PIPE_CONSUMER;
> +	pctrl.bits.p_sys_mode = BAM_PIPE_MODE_SYSTEM;
> +	pctrl.bits.p_en = 1;
> +
> +	iowrite32(pctrl.value, bdev->regs + BAM_P_CTRL(bchan->id));
> +
> +	/* set desc threshold */

Is this a TODO?
`
> +	/* do bookkeeping for tracking used EEs, used during IRQ handling */
> +	set_bit(bchan->ee, &bdev->enabled_ees);
> +
> +	bchan->head = 0;
> +	bchan->tail = 0;
> +
> +	return 0;
> +}
> +
> +/*
> + * bam_free_chan - Frees dma resources associated with specific channel
> + * @chan: specified channel
> + *
> + * Free the allocated fifo descriptor memory and channel resources
> + *
> + */
> +static void bam_free_chan(struct dma_chan *chan)
> +{
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +	struct bam_device *bdev = bchan->device;
> +	u32 val;
> +
> +	/* reset channel */
> +	iowrite32(1, bdev->regs + BAM_P_RST(bchan->id));
> +	iowrite32(0, bdev->regs + BAM_P_RST(bchan->id));
> +
> +	dma_free_coherent(bdev->dev, BAM_DESC_FIFO_SIZE, bchan->fifo_virt,
> +				bchan->fifo_phys);
> +
> +	/* mask irq for pipe/channel */
> +	val = ioread32(bdev->regs + BAM_IRQ_SRCS_MSK_EE(bchan->ee));
> +	val &= ~(1 << bchan->id);
> +	iowrite32(val, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bchan->ee));
> +
> +	/* disable irq */
> +	iowrite32(0, bdev->regs + BAM_P_IRQ_EN(bchan->id));
> +
> +	clear_bit(bchan->ee, &bdev->enabled_ees);
> +}
> +
> +/*
> + * bam_slave_config - set slave configuration for channel
> + * @chan: dma channel
> + * @cfg: slave configuration
> + *
> + * Sets slave configuration for channel
> + * Only allow setting direction once.  BAM channels are unidirectional
> + * and the direction is set in hardware.
> + *
> + */
> +static void bam_slave_config(struct bam_chan *bchan,
> +		struct bam_dma_slave_config *bcfg)
> +{
> +	struct bam_device *bdev = bchan->device;
> +
> +	bchan->bam_slave.desc_threshold = bcfg->desc_threshold;
> +
> +	/* set desc threshold */
> +	iowrite32(bcfg->desc_threshold, bdev->regs + BAM_DESC_CNT_TRSHLD);
> +}
> +
> +/*
> + * bam_start_dma - loads up descriptors and starts dma
> + * @chan: dma channel
> + *
> + * Loads descriptors into descriptor fifo and starts dma controller
> + *
> + * NOTE: Must hold channel lock
> +*/
> +static void bam_start_dma(struct bam_chan *bchan)
> +{
> +	struct bam_device *bdev = bchan->device;
> +	struct bam_async_desc *async_desc, *_adesc;
> +	u32 curr_len, val;
> +	u32 num_processed = 0;
> +
> +	if (list_empty(&bchan->pending))
> +		return;
> +
> +	curr_len = (bchan->head <= bchan->tail) ?
> +			bchan->tail - bchan->head :
> +			MAX_DESCRIPTORS - bchan->head + bchan->tail;
> +
> +	list_for_each_entry_safe(async_desc, _adesc, &bchan->pending, node) {
> +
> +		/* bust out if we are out of room */
> +		if (async_desc->num_desc + curr_len > MAX_DESCRIPTORS)
> +			break;
> +
> +		/* copy descriptors into fifo */
> +		if (bchan->tail + async_desc->num_desc > MAX_DESCRIPTORS) {
> +			u32 partial = MAX_DESCRIPTORS - bchan->tail;
> +
> +			memcpy(&bchan->fifo_virt[bchan->tail], async_desc->desc,
> +				partial * sizeof(struct bam_desc_hw));
> +			memcpy(bchan->fifo_virt, &async_desc->desc[partial],
> +				(async_desc->num_desc - partial) *
> +					sizeof(struct bam_desc_hw));
> +		} else {
> +			memcpy(&bchan->fifo_virt[bchan->tail], async_desc->desc,
> +				async_desc->num_desc *
> +				sizeof(struct bam_desc_hw));
> +		}
> +
> +		num_processed++;
> +		bchan->tail += async_desc->num_desc;
> +		bchan->tail %= MAX_DESCRIPTORS;
> +		curr_len += async_desc->num_desc;

I wonder if you could use the circ_buf API here.

> +
> +		list_move_tail(&async_desc->node, &bchan->active);
> +	}
> +
> +	/* bail if we didn't queue anything to the active queue */
> +	if (!num_processed)
> +		return;
> +
> +	async_desc = list_first_entry(&bchan->active, struct bam_async_desc,
> +			node);
> +
> +	val = ioread32(bdev->regs + BAM_P_SW_OFSTS(bchan->id));
> +	val &= P_SW_OFSTS_MASK;
> +
> +	/* kick off dma by forcing a write event to the pipe */
> +	iowrite32((bchan->tail * sizeof(struct bam_desc_hw)),
> +			bdev->regs + BAM_P_EVNT_REG(bchan->id));
> +}
> +
> +/*
> + * bam_tx_submit - Adds transaction to channel pending queue
> + * @tx: transaction to queue
> + *
> + * Adds dma transaction to pending queue for channel
> + *
> +*/
> +static dma_cookie_t bam_tx_submit(struct dma_async_tx_descriptor *tx)
> +{
> +	struct bam_chan *bchan = to_bam_chan(tx->chan);
> +	struct bam_async_desc *desc = to_bam_async_desc(tx);
> +	dma_cookie_t cookie;
> +
> +	spin_lock_bh(&bchan->lock);
> +
> +	cookie = dma_cookie_assign(tx);
> +	list_add_tail(&desc->node, &bchan->pending);
> +
> +	spin_unlock_bh(&bchan->lock);
> +
> +	return cookie;
> +}
> +
> +/*
> + * bam_prep_slave_sg - Prep slave sg transaction
> + *
> + * @chan: dma channel
> + * @sgl: scatter gather list
> + * @sg_len: length of sg
> + * @direction: DMA transfer direction
> + * @flags: DMA flags
> + * @context: transfer context (unused)
> + */
> +static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
> +	struct scatterlist *sgl, unsigned int sg_len,
> +	enum dma_transfer_direction direction, unsigned long flags,
> +	void *context)
> +{
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +	struct bam_device *bdev = bchan->device;
> +	struct bam_async_desc *async_desc = NULL;

Useless assignment? Just return NULL instead of the next 3 goto's and
this can be avoided.

> +	struct scatterlist *sg;
> +	u32 i;
> +	struct bam_desc_hw *desc;
> +
> +
> +	if (!is_slave_direction(direction)) {
> +		dev_err(bdev->dev, "invalid dma direction\n");
> +		goto err_out;
> +	}

I'm surprised the core framework doesn't do this.

> +
> +	/* direction has to match pipe configuration from the slave config */
> +	if (direction != bchan->bam_slave.slave.direction) {
> +		dev_err(bdev->dev,
> +				"trans does not match channel configuration\n");

s/trans/transfer/ ?

> +		goto err_out;
> +	}
> +
> +	/* make sure number of descriptors will fit within the fifo */
> +	if (sg_len > MAX_DESCRIPTORS) {
> +		dev_err(bdev->dev, "not enough fifo descriptor space\n");
> +		goto err_out;
> +	}
> +
> +	/* allocate enough room to accomodate the number of entries */
> +	async_desc = kzalloc(sizeof(*async_desc) +
> +			(sg_len * sizeof(struct bam_desc_hw)), GFP_KERNEL);
> +
> +	if (!async_desc) {
> +		dev_err(bdev->dev, "failed to allocate async descriptor\n");
> +		goto err_out;
> +	}
> +
> +	async_desc->num_desc = sg_len;
> +	async_desc->dir = (direction == DMA_DEV_TO_MEM) ? BAM_PIPE_PRODUCER :
> +				BAM_PIPE_CONSUMER;
> +
> +	/* fill in descriptors, align hw descriptor to 8 bytes */
> +	desc = async_desc->desc;
> +	for_each_sg(sgl, sg, sg_len, i) {
> +		if (sg_dma_len(sg) > BAM_MAX_DATA_SIZE) {
> +			dev_err(bdev->dev, "segment exceeds max size\n");
> +			goto err_out;
> +		}
> +
> +		desc->addr = sg_dma_address(sg);
> +		desc->size = sg_dma_len(sg);
> +		desc++;
> +	}
> +
> +	/* set EOT flag on last descriptor, we want IRQ on completion */
> +	async_desc->desc[async_desc->num_desc-1].flags |= DESC_FLAG_EOT;

Please add space between num_desc, dash, and 1.

> +
> +	dma_async_tx_descriptor_init(&async_desc->txd, chan);
> +	async_desc->txd.tx_submit = bam_tx_submit;
> +
> +	return &async_desc->txd;
> +
> +err_out:
> +	kfree(async_desc);
> +	return NULL;
> +}
> +
> +/*
> + * bam_dma_terminate_all - terminate all transactions
> + * @chan: dma channel
> + *
> + * Idles channel and dequeues and frees all transactions
> + * No callbacks are done
> + *
> +*/
> +static void bam_dma_terminate_all(struct dma_chan *chan)
> +{
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +	struct bam_device *bdev = bchan->device;
> +	LIST_HEAD(desc_cleanup);
> +	struct bam_async_desc *desc, *_desc;
> +
> +	spin_lock_bh(&bchan->lock);
> +
> +	/* reset channel */
> +	iowrite32(1, bdev->regs + BAM_P_RST(bchan->id));
> +	iowrite32(0, bdev->regs + BAM_P_RST(bchan->id));
> +
> +	/* grab all the descriptors and free them */
> +	list_splice_tail_init(&bchan->pending, &desc_cleanup);
> +	list_splice_tail_init(&bchan->active, &desc_cleanup);
> +
> +	list_for_each_entry_safe(desc, _desc, &desc_cleanup, node)
> +		kfree(desc);
> +
> +	spin_unlock_bh(&bchan->lock);
> +}
> +
> +/*
> + * bam_control - DMA device control
> + * @chan: dma channel
> + * @cmd: control cmd
> + * @arg: cmd argument
> + *
> + * Perform DMA control command
> + *
> +*/
> +static int bam_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> +	unsigned long arg)
> +{
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +	struct bam_device *bdev = bchan->device;
> +	struct bam_dma_slave_config *bconfig;
> +	int ret = 0;
> +
> +	switch (cmd) {
> +	case DMA_PAUSE:
> +		spin_lock_bh(&bchan->lock);
> +		iowrite32(1, bdev->regs + BAM_P_HALT(bchan->id));
> +		spin_unlock_bh(&bchan->lock);
> +		break;
> +	case DMA_RESUME:
> +		spin_lock_bh(&bchan->lock);
> +		iowrite32(0, bdev->regs + BAM_P_HALT(bchan->id));
> +		spin_unlock_bh(&bchan->lock);
> +		break;
> +	case DMA_TERMINATE_ALL:
> +		bam_dma_terminate_all(chan);
> +		break;
> +	case DMA_SLAVE_CONFIG:
> +		bconfig = (struct bam_dma_slave_config *)arg;
> +		bam_slave_config(bchan, bconfig);
> +		break;
> +	default:
> +		ret = -EIO;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +/*
> + * process_irqs_per_ee - processes the interrupts for a specific ee
> + * @bam: bam controller
> + * @ee: execution environment
> + *
> + * This function processes the interrupts for a given execution environment
> + *
> + */
> +static u32 process_irqs_per_ee(struct bam_device *bdev,
> +	u32 ee)
> +{
> +	u32 i, srcs, stts, pipe_stts;
> +	u32 clr_mask = 0;
> +
> +
> +	srcs = ioread32(bdev->regs + BAM_IRQ_SRCS_EE(ee));
> +
> +	/* check for general bam error */
> +	if (srcs & BAM_IRQ) {
> +		stts = ioread32(bdev->regs + BAM_IRQ_STTS);
> +		clr_mask |= stts;
> +	}
> +
> +	/* check pipes / channels */
> +	if (srcs & P_IRQ) {
> +
> +		for (i = 0; i < bdev->num_channels; i++) {
> +			if (srcs & (1 << i)) {
> +				/* clear pipe irq */
> +				pipe_stts = ioread32(bdev->regs +
> +					BAM_P_IRQ_STTS(i));
> +
> +				iowrite32(pipe_stts, bdev->regs +
> +					BAM_P_IRQ_CLR(i));
> +
> +				/* schedule channel work */
> +				tasklet_schedule(&bdev->channels[i].tasklet);

Maybe this little hunk inside the for loop deserves another
function because we're pretty deeply nested here. Or invert the
logic so that if (!(srcs & P_IRQ)) returns clr_mask and then this
can be less indented.

> +			}
> +		}
> +	}
> +
> +	return clr_mask;
> +}
> +
> +/*
> + * bam_dma_irq - irq handler for bam controller
> + * @irq: IRQ of interrupt
> + * @data: callback data
> + *
> + * IRQ handler for the bam controller
> + */
> +static irqreturn_t bam_dma_irq(int irq, void *data)
> +{
> +	struct bam_device *bdev = (struct bam_device *)data;

Unnecessary cast.

> +	u32 clr_mask = 0;
> +	u32 i;
> +
> +
> +	for (i = 0; i < bdev->num_ees; i++) {
> +		if (test_bit(i, &bdev->enabled_ees))
> +			clr_mask |= process_irqs_per_ee(bdev, i);
> +	}

These braces aren't really necessary.

> +
> +	iowrite32(clr_mask, bdev->regs + BAM_IRQ_CLR);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*
> + * bam_tx_status - returns status of transaction
> + * @chan: dma channel
> + * @cookie: transaction cookie
> + * @txstate: DMA transaction state
> + *
> + * Return status of dma transaction
> + */
> +static enum dma_status bam_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> +		struct dma_tx_state *txstate)
> +{
> +	return dma_cookie_status(chan, cookie, txstate);
> +}

Do we actually need this function? Can't we just assign
dma_cookie_status to device_tx_status below?

> +
> +/*
> + * dma_tasklet - DMA IRQ tasklet
> + * @data: tasklet argument (bam controller structure)
> + *
> + * Sets up next DMA operation and then processes all completed transactions
> + */
> +static void dma_tasklet(unsigned long data)
> +{
> +	struct bam_chan *bchan = (struct bam_chan *)data;
> +	struct bam_async_desc *desc, *_desc;
> +	LIST_HEAD(desc_cleanup);
> +	u32 fifo_length;
> +
> +
> +	spin_lock_bh(&bchan->lock);
> +
> +	if (list_empty(&bchan->active))
> +		goto out;
> +
> +	fifo_length = (bchan->head <= bchan->tail) ?
> +		bchan->tail - bchan->head :
> +		MAX_DESCRIPTORS - bchan->head + bchan->tail;

This is fairly complicated. Can't we just write it like this?

	if (bchan->head <= bchan->tail)
		fifo_length = bchan->tail - bchan->head;
	else
		fifo_length = MAX_DESCRIPTORS - bchan->head + bchan->tail;

> +
> +	/* only process those which are currently done */
> +	list_for_each_entry_safe(desc, _desc, &bchan->active, node) {
> +		if (desc->num_desc > fifo_length)
> +			break;
> +
> +		dma_cookie_complete(&desc->txd);
> +
> +		list_move_tail(&desc->node, &desc_cleanup);
> +		fifo_length -= desc->num_desc;
> +		bchan->head += desc->num_desc;
> +		bchan->head %= MAX_DESCRIPTORS;
> +	}
> +
> +out:
> +	/* kick off processing of any queued descriptors */
> +	bam_start_dma(bchan);
> +
> +	spin_unlock_bh(&bchan->lock);
> +
> +	/* process completed descriptors */
> +	list_for_each_entry_safe(desc, _desc, &desc_cleanup, node) {
> +		if (desc->txd.callback)
> +			desc->txd.callback(desc->txd.callback_param);
> +
> +		kfree(desc);
> +	}
> +}
> +
> +/*
> + * bam_issue_pending - starts pending transactions
> + * @chan: dma channel
> + *
> + * Calls tasklet directly which in turn starts any pending transactions
> + */
> +static void bam_issue_pending(struct dma_chan *chan)
> +{
> +	dma_tasklet((unsigned long)chan);
> +}
> +
> +struct bam_filter_args {
> +	struct dma_device *dev;
> +	u32 id;
> +	u32 ee;
> +	u32 dir;
> +};
> +
> +static bool bam_dma_filter(struct dma_chan *chan, void *data)
> +{
> +	struct bam_filter_args *args = data;
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +
> +	if (args->dev == chan->device &&
> +		args->id == bchan->id) {
> +
> +		/* we found the channel, so lets set the EE and dir */
> +		bchan->ee = args->ee;
> +		bchan->bam_slave.slave.direction = args->dir ?
> +				DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static struct dma_chan *bam_dma_xlate(struct of_phandle_args *dma_spec,
> +		struct of_dma *of)
> +{
> +	struct bam_filter_args args;
> +	dma_cap_mask_t cap;
> +
> +	if (dma_spec->args_count != 3)
> +		return NULL;
> +
> +	args.dev = of->of_dma_data;
> +	args.id = dma_spec->args[0];
> +	args.ee = dma_spec->args[1];
> +	args.dir = dma_spec->args[2];
> +
> +	dma_cap_zero(cap);
> +	dma_cap_set(DMA_SLAVE, cap);
> +
> +	return dma_request_channel(cap, bam_dma_filter, &args);
> +}
> +
> +/*
> + * bam_init
> + * @bdev: bam device
> + *
> + * Initialization helper for global bam registers
> + */
> +static int bam_init(struct bam_device *bdev)
> +{
> +	union bam_num_pipes num_pipes;
> +	union bam_ctrl ctrl;
> +	union bam_cnfg_bits cnfg_bits;
> +	union bam_revision revision;
> +
> +	/* read versioning information */
> +	revision.value = ioread32(bdev->regs + BAM_REVISION);
> +	bdev->num_ees = revision.bits.num_ees;
> +
> +	num_pipes.value = ioread32(bdev->regs + BAM_NUM_PIPES);
> +	bdev->num_channels = num_pipes.bits.bam_num_pipes;
> +
> +	/* s/w reset bam */
> +	/* after reset all pipes are disabled and idle */
> +	ctrl.value = ioread32(bdev->regs + BAM_CTRL);
> +	ctrl.bits.bam_sw_rst = 1;
> +	iowrite32(ctrl.value, bdev->regs + BAM_CTRL);
> +	ctrl.bits.bam_sw_rst = 0;
> +	iowrite32(ctrl.value, bdev->regs + BAM_CTRL);
> +
> +	/* enable bam */
> +	ctrl.bits.bam_en = 1;
> +	iowrite32(ctrl.value, bdev->regs + BAM_CTRL);
> +
> +	/* set descriptor threshhold, start with 4 bytes */
> +	iowrite32(DEFAULT_CNT_THRSHLD, bdev->regs + BAM_DESC_CNT_TRSHLD);
> +
> +	/* set config bits for h/w workarounds */
> +	/* Enable all workarounds except BAM_FULL_PIPE */
> +	cnfg_bits.value = 0xffffffff;
> +	cnfg_bits.bits.obsolete = 0;
> +	cnfg_bits.bits.obsolete2 = 0;
> +	cnfg_bits.bits.reserved = 0;
> +	cnfg_bits.bits.reserved2 = 0;
> +	cnfg_bits.bits.bam_full_pipe = 0;
> +	iowrite32(cnfg_bits.value, bdev->regs + BAM_CNFG_BITS);
> +
> +	/* enable irqs for errors */
> +	iowrite32(BAM_ERROR_EN | BAM_HRESP_ERR_EN, bdev->regs + BAM_IRQ_EN);
> +	return 0;
> +}
> +
> +static void bam_channel_init(struct bam_device *bdev, struct bam_chan *bchan,
> +	u32 index)
> +{
> +	bchan->id = index;
> +	bchan->common.device = &bdev->common;
> +	bchan->device = bdev;
> +	spin_lock_init(&bchan->lock);
> +
> +	INIT_LIST_HEAD(&bchan->pending);
> +	INIT_LIST_HEAD(&bchan->active);
> +
> +	dma_cookie_init(&bchan->common);
> +	list_add_tail(&bchan->common.device_node,
> +		&bdev->common.channels);
> +
> +	tasklet_init(&bchan->tasklet, dma_tasklet, (unsigned long)bchan);
> +
> +	/* reset channel - just to be sure */
> +	iowrite32(1, bdev->regs + BAM_P_RST(bchan->id));
> +	iowrite32(0, bdev->regs + BAM_P_RST(bchan->id));
> +}
> +
> +static int bam_dma_probe(struct platform_device *pdev)
> +{
> +	struct bam_device *bdev;
> +	int err, i;
> +
> +	bdev = kzalloc(sizeof(*bdev), GFP_KERNEL);

Please use devm_kzalloc() here to simplify error paths.

> +	if (!bdev) {
> +		dev_err(&pdev->dev, "insufficient memory for private data\n");

kmalloc calls already print errors when they fail, so this can be
removed.

> +		err = -ENOMEM;
> +		goto err_no_bdev;

Just return the error here.

> +	}
> +
> +	bdev->dev = &pdev->dev;
> +	dev_set_drvdata(bdev->dev, bdev);
> +
> +	bdev->regs = of_iomap(pdev->dev.of_node, 0);
> +	if (!bdev->regs) {
> +		dev_err(bdev->dev, "unable to ioremap base\n");
> +		err = -ENOMEM;
> +		goto err_free_bamdev;
> +	}
> +
> +	bdev->irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
> +	if (bdev->irq == NO_IRQ) {
> +		dev_err(bdev->dev, "unable to map irq\n");
> +		err = -EINVAL;
> +		goto err_unmap_mem;
> +	}

Please use platform_* APIs here, this is a platform driver after
all. Notably, use platform_get_irq() and platform_get_resource()
followed by devm_ioremap_resource().

> +
> +	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> +	if (IS_ERR(bdev->bamclk)) {
> +		err = PTR_ERR(bdev->bamclk);
> +		goto err_free_irq;
> +	}
> +
> +	err = clk_prepare_enable(bdev->bamclk);
> +	if (err) {
> +		dev_err(bdev->dev, "failed to prepare/enable clock");
> +		goto err_free_irq;
> +	}
> +
> +	err = request_irq(bdev->irq, &bam_dma_irq, IRQF_TRIGGER_HIGH, "bam_dma",
> +				bdev);

Can be devm_request_irq(). Shouldn't this be done much later in
the probe? It looks like bdev isn't fully setup yet.

> +	if (err) {
> +		dev_err(bdev->dev, "error requesting irq\n");
> +		err = -EINVAL;
> +		goto err_disable_clk;
> +	}
> +
> +	if (bam_init(bdev)) {
> +		dev_err(bdev->dev, "cannot initialize bam device\n");
> +		err = -EINVAL;
> +		goto err_disable_clk;
> +	}
> +
> +	bdev->channels = kzalloc(sizeof(*bdev->channels) * bdev->num_channels,
> +				GFP_KERNEL);
> +

We're going to have devm_kcalloc() in 3.13 so you should be able
to use that here.

> +	if (!bdev->channels) {
> +		dev_err(bdev->dev, "unable to allocate channels\n");
> +		err = -ENOMEM;
> +		goto err_disable_clk;
> +	}
> +
> +	/* allocate and initialize channels */
> +	INIT_LIST_HEAD(&bdev->common.channels);
> +
> +	for (i = 0; i < bdev->num_channels; i++)
> +		bam_channel_init(bdev, &bdev->channels[i], i);
> +
> +	/* set max dma segment size */
> +	bdev->common.dev = bdev->dev;
> +	bdev->common.dev->dma_parms = &bdev->dma_parms;
> +	if (dma_set_max_seg_size(bdev->common.dev, BAM_MAX_DATA_SIZE)) {
> +		dev_err(bdev->dev, "cannot set maximum segment size\n");
> +		goto err_disable_clk;
> +	}
> +
> +	/* set capabilities */
> +	dma_cap_zero(bdev->common.cap_mask);
> +	dma_cap_set(DMA_SLAVE, bdev->common.cap_mask);
> +
> +	/* initialize dmaengine apis */
> +	bdev->common.device_alloc_chan_resources = bam_alloc_chan;
> +	bdev->common.device_free_chan_resources = bam_free_chan;
> +	bdev->common.device_prep_slave_sg = bam_prep_slave_sg;
> +	bdev->common.device_control = bam_control;
> +	bdev->common.device_issue_pending = bam_issue_pending;
> +	bdev->common.device_tx_status = bam_tx_status;
> +	bdev->common.dev = bdev->dev;
> +
> +	dma_async_device_register(&bdev->common);

This can fail. Please check error codes.

> +
> +	if (pdev->dev.of_node) {
> +		err = of_dma_controller_register(pdev->dev.of_node,
> +				bam_dma_xlate, &bdev->common);
> +
> +		if (err) {
> +			dev_err(bdev->dev, "failed to register of_dma\n");
> +			goto err_unregister_dma;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_unregister_dma:
> +	dma_async_device_unregister(&bdev->common);
> +err_free_irq:
> +	free_irq(bdev->irq, bdev);
> +err_disable_clk:
> +	clk_disable_unprepare(bdev->bamclk);
> +err_unmap_mem:
> +	iounmap(bdev->regs);
> +err_free_bamdev:
> +	if (bdev)
> +		kfree(bdev->channels);
> +	kfree(bdev);
> +err_no_bdev:
> +	return err;
> +}
> +
> +static int bam_dma_remove(struct platform_device *pdev)
> +{
> +	struct bam_device *bdev;
> +
> +	bdev = dev_get_drvdata(&pdev->dev);
> +	dev_set_drvdata(&pdev->dev, NULL);

This is unnecessary.

> +
> +	dma_async_device_unregister(&bdev->common);
> +
> +	if (bdev) {

Ouch. We just dereferenced bdev one line before so it seems that
this check is unnecessary.

> +		free_irq(bdev->irq, bdev);
> +		clk_disable_unprepare(bdev->bamclk);
> +		iounmap(bdev->regs);
> +		kfree(bdev->channels);
> +	}
> +
> +	kfree(bdev);
> +	return 0;
> +}
[...]
> +
> +static int __init bam_dma_init(void)
> +{
> +	return platform_driver_register(&bam_dma_driver);
> +}
> +
> +static void __exit bam_dma_exit(void)
> +{
> +	return platform_driver_unregister(&bam_dma_driver);
> +}
> +
> +arch_initcall(bam_dma_init);
> +module_exit(bam_dma_exit);

module_platform_driver()? Or is there some probe deferral problem
that isn't resolved?

> +
> +MODULE_AUTHOR("Andy Gross <agross@xxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("MSM BAM DMA engine driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/dma/msm_bam_dma_priv.h b/drivers/dma/msm_bam_dma_priv.h
> new file mode 100644
> index 0000000..4d6a10c7
> --- /dev/null
> +++ b/drivers/dma/msm_bam_dma_priv.h
> @@ -0,0 +1,286 @@
> +/*
> + * Copyright (c) 2013, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +#ifndef __MSM_BAM_DMA_PRIV_H__
> +#define __MSM_BAM_DMA_PRIV_H__
> +
> +#include <linux/dmaengine.h>
> +
> +enum bam_channel_mode {
> +	BAM_PIPE_MODE_BAM2BAM = 0,	/* BAM to BAM aka device to device */
> +	BAM_PIPE_MODE_SYSTEM,		/* BAM to/from System Memory */
> +};
> +
> +enum bam_channel_dir {
> +	BAM_PIPE_CONSUMER = 0,	/* channel reads from data-fifo or memory */
> +	BAM_PIPE_PRODUCER,	/* channel writes to data-fifo or memory */
> +};
> +
> +struct bam_desc_hw {
> +	u32 addr;		/* Buffer physical address */
> +	u32 size:16;		/* Buffer size in bytes */
> +	u32 flags:16;
> +};

Is this an in memory structure that the hardware reads? It should
probably use the correct types (i.e. u16 instead of bit fields)
and then be marked as __packed__ so that compile doesn't mess
up the alignment.

> +
> +#define DESC_FLAG_INT	(1<<15)
> +#define DESC_FLAG_EOT	(1<<14)
> +#define DESC_FLAG_EOB	(1<<13)

Space around << here please. Or use the BIT() macro.

> +
> +struct bam_async_desc {
> +	struct list_head node;
> +	struct dma_async_tx_descriptor txd;
> +	u32 num_desc;
> +	enum bam_channel_dir dir;
> +	u32 fifo_pos;
> +	struct bam_desc_hw desc[0];
> +};
> +
> +static inline struct bam_async_desc *to_bam_async_desc(
> +		struct dma_async_tx_descriptor *txd)
> +{
> +	return container_of(txd, struct bam_async_desc, txd);
> +}
> +
> +
> +#define BAM_CTRL			0x0000
> +#define BAM_REVISION			0x0004
> +#define BAM_SW_REVISION			0x0080
> +#define BAM_NUM_PIPES			0x003C
> +#define BAM_TIMER			0x0040
> +#define BAM_TIMER_CTRL			0x0044
> +#define BAM_DESC_CNT_TRSHLD		0x0008
> +#define BAM_IRQ_SRCS			0x000C
> +#define BAM_IRQ_SRCS_MSK		0x0010
> +#define BAM_IRQ_SRCS_UNMASKED		0x0030
> +#define BAM_IRQ_STTS			0x0014
> +#define BAM_IRQ_CLR			0x0018
> +#define BAM_IRQ_EN			0x001C
> +#define BAM_CNFG_BITS			0x007C
> +#define BAM_IRQ_SRCS_EE(x)		(0x0800 + ((x) * 0x80))
> +#define BAM_IRQ_SRCS_MSK_EE(x)		(0x0804 + ((x) * 0x80))
> +#define BAM_P_CTRL(x)			(0x1000 + ((x) * 0x1000))
> +#define BAM_P_RST(x)			(0x1004 + ((x) * 0x1000))
> +#define BAM_P_HALT(x)			(0x1008 + ((x) * 0x1000))
> +#define BAM_P_IRQ_STTS(x)		(0x1010 + ((x) * 0x1000))
> +#define BAM_P_IRQ_CLR(x)		(0x1014 + ((x) * 0x1000))
> +#define BAM_P_IRQ_EN(x)			(0x1018 + ((x) * 0x1000))
> +#define BAM_P_EVNT_DEST_ADDR(x)		(0x182C + ((x) * 0x1000))
> +#define BAM_P_EVNT_REG(x)		(0x1818 + ((x) * 0x1000))
> +#define BAM_P_SW_OFSTS(x)		(0x1800 + ((x) * 0x1000))
> +#define BAM_P_DATA_FIFO_ADDR(x)		(0x1824 + ((x) * 0x1000))
> +#define BAM_P_DESC_FIFO_ADDR(x)		(0x181C + ((x) * 0x1000))
> +#define BAM_P_EVNT_TRSHLD(x)		(0x1828 + ((x) * 0x1000))
> +#define BAM_P_FIFO_SIZES(x)		(0x1820 + ((x) * 0x1000))

If you have the columns it might be nice to s/x/pipe/ so that it's
clear what 'x' is.

> +
> +union bam_ctrl {
> +	u32 value;
> +	struct {
> +		u32 bam_sw_rst:1;
> +		u32 bam_en:1;
> +		u32 reserved3:2;
> +		u32 bam_en_accum:1;
> +		u32 testbus_sel:7;
> +		u32 reserved2:1;
> +		u32 bam_desc_cache_sel:2;
> +		u32 bam_cached_desc_store:1;
> +		u32 ibc_disable:1;
> +		u32 reserved1:15;
> +	} bits;
> +};
> +
> +union bam_revision {
> +	u32 value;
> +	struct {
> +		u32 revision:8;
> +		u32 num_ees:4;
> +		u32 reserved1:1;
> +		u32 ce_buffer_size:1;
> +		u32 axi_active:1;
> +		u32 use_vmidmt:1;
> +		u32 secured:1;
> +		u32 bam_has_no_bypass:1;
> +		u32 high_frequency_bam:1;
> +		u32 inactiv_tmrs_exst:1;
> +		u32 num_inactiv_tmrs:1;
> +		u32 desc_cache_depth:2;
> +		u32 cmd_desc_en:1;
> +		u32 inactiv_tmr_base:8;
> +	} bits;
> +};
> +
> +union bam_sw_revision {
> +	u32 value;
> +	struct {
> +		u32 step:16;
> +		u32 minor:12;
> +		u32 major:4;
> +	} bits;
> +};
> +
> +union bam_num_pipes {
> +	u32 value;
> +	struct {
> +		u32 bam_num_pipes:8;
> +		u32 reserved:8;
> +		u32 periph_non_pipe_grp:8;
> +		u32 bam_non_pipe_grp:8;
> +	} bits;
> +};
> +
> +union bam_irq_srcs_msk {
> +	u32 value;
> +	struct {
> +		u32 p_irq_msk:31;
> +		u32 bam_irq_msk:1;
> +	} bits;
> +};
> +
> +union bam_cnfg_bits {
> +	u32 value;
> +	struct {
> +		u32 obsolete:2;
> +		u32 bam_pipe_cnfg:1;
> +		u32 obsolete2:1;
> +		u32 reserved:7;
> +		u32 bam_full_pipe:1;
> +		u32 bam_no_ext_p_rst:1;
> +		u32 bam_ibc_disable:1;
> +		u32 bam_sb_clk_req:1;
> +		u32 bam_psm_csw_req:1;
> +		u32 bam_psm_p_res:1;
> +		u32 bam_au_p_res:1;
> +		u32 bam_si_p_res:1;
> +		u32 bam_wb_p_res:1;
> +		u32 bam_wb_blk_csw:1;
> +		u32 bam_wb_csw_ack_idl:1;
> +		u32 bam_wb_retr_svpnt:1;
> +		u32 bam_wb_dsc_avl_p_rst:1;
> +		u32 bam_reg_p_en:1;
> +		u32 bam_psm_p_hd_data:1;
> +		u32 bam_au_accumed:1;
> +		u32 bam_cd_enable:1;
> +		u32 reserved2:4;
> +	} bits;
> +};
> +
> +union bam_pipe_ctrl {
> +	u32 value;
> +	struct {
> +		u32 reserved:1;
> +		u32 p_en:1;
> +		u32 reserved2:1;
> +		u32 p_direction:1;
> +		u32 p_sys_strm:1;
> +		u32 p_sys_mode:1;
> +		u32 p_auto_eob:1;
> +		u32 p_auto_eob_sel:2;
> +		u32 p_prefetch_limit:2;
> +		u32 p_write_nwd:1;
> +		u32 reserved3:4;
> +		u32 p_lock_group:5;
> +		u32 reserved4:11;
> +	} bits;
> +};

Hmm.. I believe bitfields are not portable and rely on
implementation defined behavior. The compiler is free to put
these bits in whatever order it wants. For example, you're not
guaranteed that p_en comes after reserved. Please move away from
these unions and just do the bit shifting in the code.

> +
> +/* BAM_DESC_CNT_TRSHLD */
> +#define CNT_TRSHLD		0xffff
> +#define DEFAULT_CNT_THRSHLD	0x4
> +
> +/* BAM_IRQ_SRCS */
> +#define BAM_IRQ			(0x1 << 31)
> +#define P_IRQ			0x7fffffff
> +
> +/* BAM_IRQ_SRCS_MSK */
> +#define BAM_IRQ_MSK		(0x1 << 31)
> +#define P_IRQ_MSK		0x7fffffff
> +
> +/* BAM_IRQ_STTS */
> +#define BAM_TIMER_IRQ		(0x1 << 4)
> +#define BAM_EMPTY_IRQ		(0x1 << 3)
> +#define BAM_ERROR_IRQ		(0x1 << 2)
> +#define BAM_HRESP_ERR_IRQ	(0x1 << 1)
> +
> +/* BAM_IRQ_CLR */
> +#define BAM_TIMER_CLR		(0x1 << 4)
> +#define BAM_EMPTY_CLR		(0x1 << 3)
> +#define BAM_ERROR_CLR		(0x1 << 2)
> +#define BAM_HRESP_ERR_CLR	(0x1 << 1)
> +
> +/* BAM_IRQ_EN */
> +#define BAM_TIMER_EN		(0x1 << 4)
> +#define BAM_EMPTY_EN		(0x1 << 3)
> +#define BAM_ERROR_EN		(0x1 << 2)
> +#define BAM_HRESP_ERR_EN	(0x1 << 1)
> +
> +/* BAM_P_IRQ_EN */
> +#define P_PRCSD_DESC_EN		(0x1 << 0)
> +#define P_TIMER_EN		(0x1 << 1)
> +#define P_WAKE_EN		(0x1 << 2)
> +#define P_OUT_OF_DESC_EN	(0x1 << 3)
> +#define P_ERR_EN		(0x1 << 4)
> +#define P_TRNSFR_END_EN		(0x1 << 5)
> +#define P_DEFAULT_IRQS_EN	(P_PRCSD_DESC_EN | P_ERR_EN | P_TRNSFR_END_EN)
> +
> +/* BAM_P_SW_OFSTS */
> +#define P_SW_OFSTS_MASK		0xffff
> +
> +#define BAM_DESC_FIFO_SIZE	SZ_32K
> +#define MAX_DESCRIPTORS (BAM_DESC_FIFO_SIZE / sizeof(struct bam_desc_hw) - 1)
> +#define BAM_MAX_DATA_SIZE	(SZ_32K - 8)
> +
> +struct bam_chan {
> +	struct dma_chan common;
> +	struct bam_device *device;
> +	u32 id;
> +	u32 ee;
> +	bool idle;

Is this used?

> +	struct bam_dma_slave_config bam_slave;	/* runtime configuration */
> +
> +	struct tasklet_struct tasklet;
> +	spinlock_t lock;		/* descriptor lock */
> +
> +	struct list_head pending;	/* desc pending queue */
> +	struct list_head active;	/* desc running queue */
> +
> +	struct bam_desc_hw *fifo_virt;
> +	dma_addr_t fifo_phys;
> +
> +	/* fifo markers */
> +	unsigned short head;		/* start of active descriptor entries */
> +	unsigned short tail;		/* end of active descriptor entries */
> +};
> +
> +static inline struct bam_chan *to_bam_chan(struct dma_chan *common)
> +{
> +	return container_of(common, struct bam_chan, common);
> +}
> +
> +struct bam_device {
> +	void __iomem *regs;
> +	struct device *dev;
> +	struct dma_device common;
> +	struct device_dma_parameters dma_parms;
> +	struct bam_chan *channels;
> +	u32 num_channels;
> +	u32 num_ees;
> +	unsigned long enabled_ees;
> +	u32 feature;

Is this used?

> +	int irq;
> +	struct clk *bamclk;
> +};
> +
> +static inline struct bam_device *to_bam_device(struct dma_device *common)
> +{
> +	return container_of(common, struct bam_device, common);
> +}
> +
> +#endif /* __MSM_BAM_DMA_PRIV_H__ */

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