Re: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller

[Vinod Koul]

On Tue, Sep 26, 2017 at 02:22:05AM +0300, Dmitry Osipenko wrote:

> +config TEGRA20_AHB_DMA
> +	tristate "NVIDIA Tegra20 AHB DMA support"
> +	depends on ARCH_TEGRA

Can we add COMPILE_TEST, helps me compile drivers

> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>

no vchan.h, so i presume we are not using that here, any reason why?

> +
> +#include "dmaengine.h"
> +
> +#define TEGRA_AHBDMA_CMD			0x0
> +#define TEGRA_AHBDMA_CMD_ENABLE			BIT(31)
> +
> +#define TEGRA_AHBDMA_IRQ_ENB_MASK		0x20
> +#define TEGRA_AHBDMA_IRQ_ENB_CH(ch)		BIT(ch)
> +
> +#define TEGRA_AHBDMA_CHANNEL_BASE(ch)		(0x1000 + (ch) * 0x20)
> +
> +#define TEGRA_AHBDMA_CHANNEL_CSR		0x0
> +#define TEGRA_AHBDMA_CHANNEL_ADDR_WRAP		BIT(18)
> +#define TEGRA_AHBDMA_CHANNEL_FLOW		BIT(24)
> +#define TEGRA_AHBDMA_CHANNEL_ONCE		BIT(26)
> +#define TEGRA_AHBDMA_CHANNEL_DIR_TO_XMB		BIT(27)
> +#define TEGRA_AHBDMA_CHANNEL_IE_EOC		BIT(30)
> +#define TEGRA_AHBDMA_CHANNEL_ENABLE		BIT(31)
> +#define TEGRA_AHBDMA_CHANNEL_REQ_SEL_SHIFT	16
> +#define TEGRA_AHBDMA_CHANNEL_WCOUNT_MASK	0xFFFC

GENMASK() ?

> +static void tegra_ahbdma_tasklet(unsigned long data)
> +{
> +	struct tegra_ahbdma_tx_desc *tx = (struct tegra_ahbdma_tx_desc *)data;
> +	struct dma_async_tx_descriptor *desc = &tx->desc;
> +
> +	dmaengine_desc_get_callback_invoke(desc, NULL);
> +
> +	if (!tx->cyclic && !dmaengine_desc_test_reuse(desc))
> +		kfree(tx);

lot of code here can be reduced if we use vchan

> +static struct dma_async_tx_descriptor *tegra_ahbdma_prep_dma_cyclic(
> +					struct dma_chan *chan,
> +					dma_addr_t buf_addr,
> +					size_t buf_len,
> +					size_t period_len,
> +					enum dma_transfer_direction dir,
> +					unsigned long flags)
> +{
> +	struct tegra_ahbdma_tx_desc *tx;
> +
> +	/* unimplemented */
> +	if (buf_len != period_len || buf_len > SZ_64K)
> +		return NULL;
> +
> +	tx = kzalloc(sizeof(*tx), GFP_KERNEL);
> +	if (!tx)
> +		return NULL;
> +
> +	dma_async_tx_descriptor_init(&tx->desc, chan);
> +
> +	tx->desc.tx_submit	= tegra_ahbdma_tx_submit;
> +	tx->mem_paddr		= buf_addr;
> +	tx->size		= buf_len;
> +	tx->flags		= flags;
> +	tx->cyclic		= true;
> +	tx->dir			= dir;
> +
> +	tasklet_init(&tx->tasklet, tegra_ahbdma_tasklet, (unsigned long)tx);

why not precalulcate the register settings here. While submitting you are in
hot path keeping dmaengine idle so faster you can submit, better the perf

> +static void tegra_ahbdma_issue_pending(struct dma_chan *chan)
> +{
> +	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
> +	struct tegra_ahbdma_tx_desc *tx;
> +	struct list_head *entry, *tmp;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&ahbdma_chan->lock, flags);
> +
> +	list_for_each_safe(entry, tmp, &ahbdma_chan->pending_list)
> +		list_move_tail(entry, &ahbdma_chan->active_list);
> +
> +	if (completion_done(&ahbdma_chan->idling)) {
> +		tx = list_first_entry_or_null(&ahbdma_chan->active_list,
> +					      struct tegra_ahbdma_tx_desc,
> +					      node);
> +		if (tx) {
> +			tegra_ahbdma_submit_tx(ahbdma_chan, tx);

what is chan is already running?

> +			reinit_completion(&ahbdma_chan->idling);
> +		}
> +	}
> +
> +	spin_unlock_irqrestore(&ahbdma_chan->lock, flags);
> +}
> +
> +static enum dma_status tegra_ahbdma_tx_status(struct dma_chan *chan,
> +					      dma_cookie_t cookie,
> +					      struct dma_tx_state *state)
> +{
> +	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
> +	struct tegra_ahbdma_tx_desc *tx;
> +	enum dma_status cookie_status;
> +	unsigned long flags;
> +	size_t residual;
> +	u32 status;
> +
> +	spin_lock_irqsave(&ahbdma_chan->lock, flags);
> +
> +	cookie_status = dma_cookie_status(chan, cookie, state);
> +	if (cookie_status != DMA_COMPLETE) {

residue can be NULL so check it before proceeding ahead

> +static int tegra_ahbdma_config(struct dma_chan *chan,
> +			       struct dma_slave_config *sconfig)
> +{
> +	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
> +	enum dma_transfer_direction dir = sconfig->direction;
> +	u32 burst, ahb_seq, ahb_addr;
> +
> +	if (sconfig->src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES ||
> +	    sconfig->dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> +		return -EINVAL;
> +
> +	if (dir == DMA_DEV_TO_MEM) {
> +		burst    = sconfig->src_maxburst;
> +		ahb_addr = sconfig->src_addr;
> +	} else {
> +		burst    = sconfig->dst_maxburst;
> +		ahb_addr = sconfig->dst_addr;
> +	}
> +
> +	switch (burst) {
> +	case 1: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_1; break;
> +	case 4: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_4; break;
> +	case 8: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_8; break;

pls make this statement and break on subsequent lines, readablity matters

> +	default:
> +		return -EINVAL;
> +	}
> +
> +	ahb_seq  = burst << TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT;
> +	ahb_seq |= TEGRA_AHBDMA_CHANNEL_ADDR_WRAP;
> +	ahb_seq |= TEGRA_AHBDMA_CHANNEL_INTR_ENB;
> +
> +	writel_relaxed(ahb_seq,
> +		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_SEQ);
> +
> +	writel_relaxed(ahb_addr,
> +		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_PTR);

oh no, you don't write to HW here. This can be called anytime when you have
txn running! You should save these and use them in prep_ calls.

> +static int tegra_ahbdma_remove(struct platform_device *pdev)
> +{
> +	struct tegra_ahbdma *tdma = platform_get_drvdata(pdev);
> +
> +	of_dma_controller_free(pdev->dev.of_node);
> +	dma_async_device_unregister(&tdma->dma_dev);
> +	clk_disable_unprepare(tdma->clk);

not ensuring tasklets are killed and irq is freed so no more tasklets can
run? I think that needs to be done...

> +MODULE_DESCRIPTION("NVIDIA Tegra AHB DMA Controller driver");
> +MODULE_AUTHOR("Dmitry Osipenko <digetx@xxxxxxxxx>");
> +MODULE_LICENSE("GPL");

MODULE_ALIAS?

-- 
~Vinod