Re: [PATCH 2/2] dmaengine: mediatek: Add MediaTek Command-Queue DMA controller for MT6765 SoC

[Sean Wang]

On Tue, 2018-09-04 at 16:43 +0800, shun-chih.yu@xxxxxxxxxxxx wrote:
> From: Shun-Chih Yu <shun-chih.yu@xxxxxxxxxxxx>
> 
> MediaTek Command-Queue DMA controller (CQDMA) on MT6765 SoC is dedicated
> to memory-to-memory transfer through queue based descriptor management.
> 
> There are only 3 physical channels inside CQDMA, while the driver is
> extended to support 32 virtual channels for multiple dma users to issue
> dma requests onto the CQDMA simultaneously.
> 
> Signed-off-by: Shun-Chih Yu <shun-chih.yu@xxxxxxxxxxxx>
> ---
>  drivers/dma/mediatek/Kconfig     |   12 +
>  drivers/dma/mediatek/Makefile    |    1 +
>  drivers/dma/mediatek/mtk-cqdma.c |  952 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 965 insertions(+)
>  create mode 100644 drivers/dma/mediatek/mtk-cqdma.c
> 
> diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
> index 27bac0b..4a1582d 100644
> --- a/drivers/dma/mediatek/Kconfig
> +++ b/drivers/dma/mediatek/Kconfig
> @@ -11,3 +11,15 @@ config MTK_HSDMA
>  	  This controller provides the channels which is dedicated to
>  	  memory-to-memory transfer to offload from CPU through ring-
>  	  based descriptor management.
> +
> +config MTK_CQDMA
> +	tristate "MediaTek Command-Queue DMA controller support"
> +	depends on ARCH_MEDIATEK || COMPILE_TEST
> +	select DMA_ENGINE
> +	select DMA_VIRTUAL_CHANNELS
> +	help
> +	  Enable support for Command-Queue DMA controller on MediaTek
> +	  SoCs.
> +
> +	  This controller provides the channels which is dedicated to
> +	  memory-to-memory transfer to offload from CPU.
> diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
> index 6e778f8..41bb381 100644
> --- a/drivers/dma/mediatek/Makefile
> +++ b/drivers/dma/mediatek/Makefile
> @@ -1 +1,2 @@
>  obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
> +obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
> diff --git a/drivers/dma/mediatek/mtk-cqdma.c b/drivers/dma/mediatek/mtk-cqdma.c
> new file mode 100644
> index 0000000..c74aaa3
> --- /dev/null
> +++ b/drivers/dma/mediatek/mtk-cqdma.c
> @@ -0,0 +1,952 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2018-2019 MediaTek Inc.
> +
> +/*
> + * Driver for MediaTek Command-Queue DMA Controller
> + *
> + * Author: Shun-Chih Yu <shun-chih.yu@xxxxxxxxxxxx>
> + *
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/iopoll.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/refcount.h>
> +#include <linux/slab.h>
> +
> +#include "../virt-dma.h"
> +
> +#define MTK_CQDMA_USEC_POLL		10
> +#define MTK_CQDMA_TIMEOUT_POLL		1000
> +#define MTK_CQDMA_DMA_BUSWIDTHS		BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)
> +#define MTK_CQDMA_ALIGN_SIZE		1
> +
> +/* The default number of virtual channel */
> +#define MTK_CQDMA_NR_VCHANS		3
> +

commit message mentions there are 32 virtual channels available

> +/* The default number of physical channel */
> +#define MTK_CQDMA_NR_PCHANS		3
> +
> +/* Registers for underlying dma manipulation */
> +#define MTK_CQDMA_INT_FLAG		0x0
> +#define MTK_CQDMA_INT_EN		0x4
> +#define MTK_CQDMA_EN			0x8
> +#define MTK_CQDMA_RESET			0xc
> +#define MTK_CQDMA_STOP			0x10
> +#define MTK_CQDMA_FLUSH			0x14
> +#define MTK_CQDMA_SRC			0x1c
> +#define MTK_CQDMA_DST			0x20
> +#define MTK_CQDMA_LEN1			0x24
> +#define MTK_CQDMA_LEN2			0x28
> +#define MTK_CQDMA_SRC2			0x60
> +#define MTK_CQDMA_DST2			0x64
> +
> +/* Registers setting */
> +#define MTK_CQDMA_EN_BIT		BIT(0)
> +#define MTK_CQDMA_INT_FLAG_BIT		BIT(0)
> +#define MTK_CQDMA_INT_EN_BIT		BIT(0)
> +#define MTK_CQDMA_FLUSH_BIT		BIT(0)
> +
> +#define MTK_CQDMA_WARM_RST_BIT		BIT(0)
> +#define MTK_CQDMA_HARD_RST_BIT		BIT(1)
> +
> +#define MTK_CQDMA_MAX_LEN		(0xfffffff)
> +#define MTK_CQDMA_ADDR_LIMIT		(0xffffffff)
> +#define MTK_CQDMA_ADDR2_SHFIT		(32)

remove these unused macros

> +
> +/**
> + * struct mtk_cqdma_vdesc - The struct holding info describing physical
> + *                         descriptor (PD)
> + * @len:                   The total data size device wants to move
> + * @src:                   The source address device wants to move from
> + * @dest:                  The destination address device wants to move to
> + */
> +struct mtk_cqdma_pdesc {
> +	size_t len;
> +	dma_addr_t src;
> +	dma_addr_t dest;
> +};
> +
> +/**
> + * struct mtk_cqdma_vdesc - The struct holding info describing virtual
> + *                         descriptor (VD)
> + * @vd:                    An instance for struct virt_dma_desc
> + * @len:                   The total data size device wants to move
> + * @residue:               The remaining data size device will move
> + * @dest:                  The destination address device wants to move to
> + * @src:                   The source address device wants to move from
> + * @ch:                    The pointer to the corresponding dma channel
> + * @pd_list		   The array for PDs
> + * @pd_list_len		   The size of PD list
> + * @pd_list_ptr            The index of the PD being processed
> + * @node                   The lise_head struct to build link-list for VDs
> + */
> +struct mtk_cqdma_vdesc {
> +	struct virt_dma_desc vd;
> +	size_t len;
> +	size_t residue;
> +	dma_addr_t dest;
> +	dma_addr_t src;

you already have src, dest, and len kept in cqdma_pdesc, i thought we can reuse them instead of holding another copy here

> +	struct dma_chan *ch;
> +
> +	size_t pd_list_len;
> +	size_t pd_list_ptr;
> +	struct mtk_cqdma_pdesc **pd_list;
> +
> +	struct list_head node;

you create another list to hold descriptors in the driver, 

in general, you can totally use list desc_[allocated, submitted, issued, and completed] vchan provides to mainatain the cycle of descriptors.

> +};
> +
> +/**
> + * struct mtk_cqdma_pchan - The struct holding info describing physical
> + *                         channel (PC)
> + * @queue:                 Queue for the PDs issued to this PC
> + * @base:                  The mapped register I/O base of this PC
> + * @irq:                   The IRQ that this PC are using
> + * @refcnt:                Track how many VCs are using this PC
> + * @lock:                  Lock protect agaisting multiple VCs access PC
> + */
> +struct mtk_cqdma_pchan {
> +	struct list_head queue;
> +	void __iomem *base;
> +	u32 irq;
> +
> +	refcount_t refcnt;
> +
> +	/* lock to protect PC */
> +	spinlock_t lock;
> +};
> +
> +/**
> + * struct mtk_cqdma_vchan - The struct holding info describing virtual
> + *                         channel (VC)
> + * @vc:                    An instance for struct virt_dma_chan
> + * @pc:                    The pointer to the underlying PC
> + * @issue_completion:	   The wait for all issued descriptors completited
> + * @issue_synchronize:	   Bool indicating channel synchronization starts
> + */
> +struct mtk_cqdma_vchan {
> +	struct virt_dma_chan vc;
> +	struct mtk_cqdma_pchan *pc;
> +	struct completion issue_completion;
> +	bool issue_synchronize;
> +};
> +
> +/**
> + * struct mtk_cqdma_device - The struct holding info describing CQDMA
> + *                          device
> + * @ddev:                   An instance for struct dma_device
> + * @clk:                    The clock that device internal is using
> + * @dma_requests:           The number of VCs the device supports to
> + * @dma_channels:           The number of PCs the device supports to
> + * @vc:                     The pointer to all available VCs
> + * @pc:                     The pointer to all the underlying PCs
> + */
> +struct mtk_cqdma_device {
> +	struct dma_device ddev;
> +	struct clk *clk;
> +
> +	u32 dma_requests;
> +	u32 dma_channels;
> +	struct mtk_cqdma_vchan *vc;
> +	struct mtk_cqdma_pchan **pc;
> +};
> +
> +static struct mtk_cqdma_device *to_cqdma_dev(struct dma_chan *chan)
> +{
> +	return container_of(chan->device, struct mtk_cqdma_device, ddev);
> +}
> +
> +static struct mtk_cqdma_vchan *to_cqdma_vchan(struct dma_chan *chan)
> +{
> +	return container_of(chan, struct mtk_cqdma_vchan, vc.chan);
> +}
> +
> +static struct mtk_cqdma_vdesc *to_cqdma_vdesc(struct virt_dma_desc *vd)
> +{
> +	return container_of(vd, struct mtk_cqdma_vdesc, vd);
> +}
> +
> +static struct device *cqdma2dev(struct mtk_cqdma_device *cqdma)
> +{
> +	return cqdma->ddev.dev;
> +}
> +
> +static u32 mtk_dma_read(struct mtk_cqdma_pchan *pc, u32 reg)
> +{
> +	return readl(pc->base + reg);
> +}
> +
> +static void mtk_dma_write(struct mtk_cqdma_pchan *pc, u32 reg, u32 val)
> +{
> +	writel_relaxed(val, pc->base + reg);
> +}
> +
> +static void mtk_dma_rmw(struct mtk_cqdma_pchan *pc, u32 reg,
> +			u32 mask, u32 set)
> +{
> +	u32 val;
> +
> +	val = mtk_dma_read(pc, reg);
> +	val &= ~mask;
> +	val |= set;
> +	mtk_dma_write(pc, reg, val);
> +}
> +
> +static void mtk_dma_set(struct mtk_cqdma_pchan *pc, u32 reg, u32 val)
> +{
> +	mtk_dma_rmw(pc, reg, 0, val);
> +}
> +
> +static void mtk_dma_clr(struct mtk_cqdma_pchan *pc, u32 reg, u32 val)
> +{
> +	mtk_dma_rmw(pc, reg, val, 0);
> +}
> +
> +static void mtk_cqdma_vdesc_free(struct virt_dma_desc *vd)
> +{
> +	struct mtk_cqdma_vdesc *cvd = to_cqdma_vdesc(vd);
> +	size_t i;
> +
> +	/* free PD list */
> +	for (i = 0; i < cvd->pd_list_len; ++i)
> +		kfree(cvd->pd_list[i]);
> +	kfree(cvd->pd_list);
> +
> +	/* free VD */
> +	kfree(cvd);
> +}
> +
> +static int mtk_cqdma_poll_engine_done(struct mtk_cqdma_pchan *pc)
> +{
> +	u32 status = 0;
> +
> +	return readl_poll_timeout(pc->base + MTK_CQDMA_EN, status,
> +				  !(status & MTK_CQDMA_EN_BIT),
> +				  MTK_CQDMA_USEC_POLL,
> +				  MTK_CQDMA_TIMEOUT_POLL);
> +}
> +
> +static int mtk_cqdma_warm_reset(struct mtk_cqdma_pchan *pc)
> +{
> +	mtk_dma_set(pc, MTK_CQDMA_RESET, MTK_CQDMA_WARM_RST_BIT);
> +
> +	return mtk_cqdma_poll_engine_done(pc);
> +}
> +
> +static int mtk_cqdma_hard_reset(struct mtk_cqdma_pchan *pc)
> +{
> +	mtk_dma_set(pc, MTK_CQDMA_RESET, MTK_CQDMA_HARD_RST_BIT);
> +	mtk_dma_clr(pc, MTK_CQDMA_RESET, MTK_CQDMA_HARD_RST_BIT);
> +
> +	return mtk_cqdma_poll_engine_done(pc);
> +}
> +
> +static void mtk_cqdma_start(struct mtk_cqdma_pchan *pc)
> +{
> +	mtk_dma_set(pc, MTK_CQDMA_EN, MTK_CQDMA_EN_BIT);

there is only a user for the function and the logic is quite simple, so lets merge into where the user is

> +}
> +
> +static int mtk_cqdma_stop(struct mtk_cqdma_pchan *pc)
> +{
> +	int err;
> +
> +	mtk_dma_set(pc, MTK_CQDMA_FLUSH, MTK_CQDMA_FLUSH_BIT);
> +
> +	err = mtk_cqdma_poll_engine_done(pc);
> +
> +	mtk_dma_clr(pc, MTK_CQDMA_FLUSH, MTK_CQDMA_FLUSH_BIT);
> +	mtk_dma_clr(pc, MTK_CQDMA_INT_FLAG, MTK_CQDMA_INT_FLAG_BIT);
> +
> +	return err;

there is only a user for the function and the logic is quite simple, so lets merge into where the user is

> +}
> +
> +static void mtk_cqdma_set_tran(struct mtk_cqdma_pchan *pc, dma_addr_t src,
> +			       dma_addr_t dest, size_t len)
> +{
> +	/* setup source */
> +	mtk_dma_set(pc, MTK_CQDMA_SRC, src & MTK_CQDMA_ADDR_LIMIT);
> +	mtk_dma_set(pc, MTK_CQDMA_SRC2, src >> MTK_CQDMA_ADDR2_SHFIT);
> +
> +	/* setup destination */
> +	mtk_dma_set(pc, MTK_CQDMA_DST, dest & MTK_CQDMA_ADDR_LIMIT);
> +	mtk_dma_set(pc, MTK_CQDMA_DST2, dest >> MTK_CQDMA_ADDR2_SHFIT);
> +
> +	/* setup length */
> +	mtk_dma_set(pc, MTK_CQDMA_LEN1, len);

there is only a user for the function and the logic is quite simple, so lets merge into where the user is

> +}
> +
> +static void mtk_cqdma_alloc_pchan(struct mtk_cqdma_pchan *pc)
> +{
> +	/* hard reset the dma engine */
> +	mtk_cqdma_hard_reset(pc);
> +
> +	/* enable interrupt for this PC */
> +	mtk_dma_set(pc, MTK_CQDMA_INT_EN, MTK_CQDMA_INT_EN_BIT);

there is only a user for the function and the logic is quite simple, so lets merge into where the user is

> +}
> +
> +static void mtk_cqdma_free_pchan(struct mtk_cqdma_pchan *pc)
> +{
> +	/* stop the engine and wait for engine stop */
> +	if (mtk_cqdma_stop(pc) < 0)
> +		pr_warn("cqdma stop timeout\n");

dev_err

> +	/* disable interrupt for this PC */
> +	mtk_dma_clr(pc, MTK_CQDMA_INT_EN, MTK_CQDMA_INT_EN_BIT);

there is only a user for the function and the logic is quite simple, so lets merge into where the user is

> +}
> +
> +static void mtk_cqdma_start_tran(struct mtk_cqdma_pchan *pc,
> +				 struct mtk_cqdma_pdesc *cpd)
> +{
> +	/* reset the dma engine for the transaction */
> +	if (mtk_cqdma_warm_reset(pc) < 0)
> +		pr_warn("cqdma warm reset timeout\n");

dev_err

> +
> +	/* setup dma engine for this PD */
> +	mtk_cqdma_set_tran(pc, cpd->src, cpd->dest, cpd->len);
> +
> +	/* start dma engine */
> +	mtk_cqdma_start(pc);
> +}
> +
> +static int mtk_cqdma_issue_pending_vdesc(struct mtk_cqdma_device *cqdma,
> +					 struct mtk_cqdma_pchan *pc,
> +					 struct mtk_cqdma_vdesc *cvd)
> +{
> +	bool trigger_engine = false;
> +
> +	if (!cvd->pd_list)
> +		return 0;
> +
> +	lockdep_assert_held(&pc->lock);
> +
> +	/* need to trigger dma engine if PC's queue is empty */
> +	if (list_empty(&pc->queue))
> +		trigger_engine = true;
> +
> +	/* add VD into PC's queue */
> +	list_add_tail(&cvd->node, &pc->queue);

the hardware only can handle a descriptor at a time

so I thought the pc->queue seems complete no need, instead, you can just get a descriptor from ->desc_issued list to handle
, leave others descriptors still in ->desc_issued list until the the active descriptor finishes and then fire them
in sequence.

> +
> +	/* start transaction for this VD */
> +	if (trigger_engine)
> +		mtk_cqdma_start_tran(pc, cvd->pd_list[cvd->pd_list_ptr]);
> +
> +	return 0;
> +}
> +
> +static void mtk_cqdma_issue_vchan_pending(struct mtk_cqdma_device *cqdma,
> +					  struct mtk_cqdma_vchan *cvc)
> +{
> +	struct virt_dma_desc *vd, *vd2;
> +	int err;
> +
> +	lockdep_assert_held(&cvc->vc.lock);
> +
> +	list_for_each_entry_safe(vd, vd2, &cvc->vc.desc_issued, node) {
> +		struct mtk_cqdma_vdesc *cvd;
> +
> +		cvd = to_cqdma_vdesc(vd);
> +
> +		/* issue VD to PC's queue */
> +		err = mtk_cqdma_issue_pending_vdesc(cqdma, cvc->pc, cvd);
> +
> +		if (err == -ENOSPC)

the error seems never happens 

> +			break;
> +
> +		/* remove VD from list desc_issued */
> +		list_del(&vd->node);
> +	}
> +}
> +
> +/*
> + * return true if this VC is active,
> + * meaning that there are VDs under processing by the PC
> + */
> +static bool mtk_cqdma_is_vchan_active(struct mtk_cqdma_vchan *cvc)
> +{
> +	struct mtk_cqdma_vdesc *cvd;
> +
> +	list_for_each_entry(cvd, &cvc->pc->queue, node)
> +		if (cvc == to_cqdma_vchan(cvd->ch))
> +			return true;
> +
> +	return false;
> +}
> +
> +static void mtk_cqdma_consume_work_queue(struct mtk_cqdma_pchan *pc)
> +{
> +	struct mtk_cqdma_vchan *cvc;
> +	struct mtk_cqdma_vdesc *cvd;
> +
> +	/* consume a VD from queue */
> +	cvd = list_first_entry_or_null(&pc->queue,
> +				       struct mtk_cqdma_vdesc, node);
> +	if (unlikely(!cvd))
> +		return;
> +
> +	/* update residue of VD */
> +	cvd->residue -= cvd->pd_list[cvd->pd_list_ptr]->len;
> +
> +	cvc = to_cqdma_vchan(cvd->ch);
> +
> +	if (cvd->pd_list_ptr == cvd->pd_list_len - 1) {
> +		/* delete VD from queue if its PD list completed */
> +		list_del(&cvd->node);
> +
> +		spin_lock(&cvc->vc.lock);
> +
> +		/* add VD into list desc_completed */
> +		vchan_cookie_complete(&cvd->vd);
> +
> +		/* setup completion if this VC is under synchronization */
> +		if (cvc->issue_synchronize && !mtk_cqdma_is_vchan_active(cvc)) {
> +			complete(&cvc->issue_completion);
> +			cvc->issue_synchronize = false;
> +		}
> +
> +		spin_unlock(&cvc->vc.lock);
> +	} else {
> +		/* there are physical descs queueing to be served */
> +		cvd->pd_list_ptr++;
> +	}
> +
> +	/* start transaction for next PD if queue is not empty */
> +	cvd = list_first_entry_or_null(&pc->queue,
> +				       struct mtk_cqdma_vdesc, node);
> +	if (cvd)
> +		mtk_cqdma_start_tran(pc, cvd->pd_list[cvd->pd_list_ptr]);

I really thinks reuse desc_issued list can simplify the whole logic, otherwise you should 

take care the synchronization between desc_completed list and pc->queue

> +}
> +
> +static irqreturn_t mtk_cqdma_irq(int irq, void *devid)
> +{
> +	struct mtk_cqdma_device *cqdma = devid;
> +	irqreturn_t ret = IRQ_NONE;
> +	u32 i;
> +
> +	/* clear interrupt flags for each PC */
> +	for (i = 0; i < cqdma->dma_channels; ++i) {
> +		spin_lock(&cqdma->pc[i]->lock);
> +		if (mtk_dma_read(cqdma->pc[i],
> +				 MTK_CQDMA_INT_FLAG) & MTK_CQDMA_INT_FLAG_BIT) {
> +			/* clear interrupt */
> +			mtk_dma_clr(cqdma->pc[i], MTK_CQDMA_INT_FLAG,
> +				    MTK_CQDMA_INT_FLAG_BIT);
> +
> +			/* consume the queue */
> +			mtk_cqdma_consume_work_queue(cqdma->pc[i]);
> +			ret = IRQ_HANDLED;
> +		}
> +		spin_unlock(&cqdma->pc[i]->lock);
> +	}
> +
> +	return ret;
> +}
> +
> +static struct virt_dma_desc *mtk_cqdma_find_active_desc(struct dma_chan *c,
> +							dma_cookie_t cookie)
> +{
> +	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> +	struct virt_dma_desc *vd;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&cvc->pc->lock, flags);
> +	list_for_each_entry(vd, &cvc->pc->queue, node)
> +		if (vd->tx.cookie == cookie) {
> +			spin_unlock_irqrestore(&cvc->pc->lock, flags);
> +			return vd;
> +		}
> +	spin_unlock_irqrestore(&cvc->pc->lock, flags);
> +
> +	list_for_each_entry(vd, &cvc->vc.desc_issued, node)
> +		if (vd->tx.cookie == cookie)
> +			return vd;
> +
> +	return NULL;
> +}
> +
> +static enum dma_status mtk_cqdma_tx_status(struct dma_chan *c,
> +					   dma_cookie_t cookie,
> +					   struct dma_tx_state *txstate)
> +{
> +	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> +	struct mtk_cqdma_vdesc *cvd;
> +	struct virt_dma_desc *vd;
> +	enum dma_status ret;
> +	unsigned long flags;
> +	size_t bytes = 0;
> +
> +	ret = dma_cookie_status(c, cookie, txstate);
> +	if (ret == DMA_COMPLETE || !txstate)
> +		return ret;
> +
> +	spin_lock_irqsave(&cvc->vc.lock, flags);
> +	vd = mtk_cqdma_find_active_desc(c, cookie);
> +	spin_unlock_irqrestore(&cvc->vc.lock, flags);
> +
> +	if (vd) {
> +		cvd = to_cqdma_vdesc(vd);
> +		bytes = cvd->residue;
> +	}
> +
> +	dma_set_residue(txstate, bytes);
> +
> +	return ret;
> +}
> +
> +static void mtk_cqdma_issue_pending(struct dma_chan *c)
> +{
> +	struct mtk_cqdma_device *cqdma = to_cqdma_dev(c);
> +	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> +	unsigned long pc_flags;
> +	unsigned long vc_flags;
> +
> +	/* acquire PC's lock first due to lock dependency in ISR */
> +	spin_lock_irqsave(&cvc->pc->lock, pc_flags);
> +	spin_lock_irqsave(&cvc->vc.lock, vc_flags);
> +
> +	if (vchan_issue_pending(&cvc->vc))
> +		mtk_cqdma_issue_vchan_pending(cqdma, cvc);
> +
> +	spin_unlock_irqrestore(&cvc->vc.lock, vc_flags);
> +	spin_unlock_irqrestore(&cvc->pc->lock, pc_flags);
> +}
> +
> +static struct dma_async_tx_descriptor *
> +mtk_cqdma_prep_dma_memcpy(struct dma_chan *c, dma_addr_t dest,
> +			  dma_addr_t src, size_t len, unsigned long flags)
> +{
> +	struct mtk_cqdma_vdesc *cvd;
> +	size_t pd_list_len, tlen, i;
> +
> +	cvd = kzalloc(sizeof(*cvd), GFP_NOWAIT);
> +	if (!cvd)
> +		return NULL;
> +
> +	/* setup dma channel */
> +	cvd->ch = c;
> +
> +	/* setup sourece, destination, and length */
> +	cvd->len = len;
> +	cvd->residue = len;
> +	cvd->src = src;
> +	cvd->dest = dest;
> +
> +	/* setup PD list */
> +	pd_list_len = DIV_ROUND_UP(len, MTK_CQDMA_MAX_LEN);
> +	cvd->pd_list_len = pd_list_len;
> +	cvd->pd_list_ptr = 0;
> +
> +	cvd->pd_list = kcalloc(pd_list_len, sizeof(struct mtk_cqdma_pdesc **),
> +			       GFP_NOWAIT);
> +	if (!cvd->pd_list) {
> +		kfree(cvd);
> +		return NULL;
> +	}
> +
> +	for (i = 0; i < pd_list_len; ++i) {
> +		cvd->pd_list[i] = kzalloc(sizeof(struct mtk_cqdma_pdesc *),
> +					  GFP_NOWAIT);
> +		if (!cvd->pd_list[i]) {
> +			for (; i > 0; --i)
> +				kfree(cvd->pd_list[i - 1]);
> +			kfree(cvd->pd_list);
> +			kfree(cvd);
> +			return NULL;
> +		}
> +
> +		tlen = (len > MTK_CQDMA_MAX_LEN) ? MTK_CQDMA_MAX_LEN : len;
> +
> +		cvd->pd_list[i]->src = cvd->src + cvd->len - tlen;
> +		cvd->pd_list[i]->dest = cvd->dest + cvd->len - tlen;
> +		cvd->pd_list[i]->len = tlen;
> +		len -= tlen;
> +	}
> +
> +	return vchan_tx_prep(to_virt_chan(c), &cvd->vd, flags);
> +}
> +
> +static void mtk_cqdma_free_inactive_desc(struct dma_chan *c)
> +{
> +	struct virt_dma_chan *vc = to_virt_chan(c);
> +	unsigned long flags;
> +	LIST_HEAD(head);
> +
> +	/*
> +	 * set desc_allocated, desc_submitted,
> +	 * and desc_issued as the candicates to be freed
> +	 */
> +	spin_lock_irqsave(&vc->lock, flags);
> +	list_splice_tail_init(&vc->desc_allocated, &head);
> +	list_splice_tail_init(&vc->desc_submitted, &head);
> +	list_splice_tail_init(&vc->desc_issued, &head);
> +	spin_unlock_irqrestore(&vc->lock, flags);
> +
> +	/* free descriptor lists */
> +	vchan_dma_desc_free_list(vc, &head);
> +}
> +
> +static void mtk_cqdma_free_active_desc(struct dma_chan *c)
> +{
> +	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> +	bool sync_needed = false;
> +	unsigned long pc_flags;
> +	unsigned long vc_flags;
> +
> +	/* acquire PC's lock first due to lock dependency in dma ISR */
> +	spin_lock_irqsave(&cvc->pc->lock, pc_flags);
> +	spin_lock_irqsave(&cvc->vc.lock, vc_flags);
> +
> +	/* synchronization is required if this VC is active */
> +	if (mtk_cqdma_is_vchan_active(cvc)) {
> +		cvc->issue_synchronize = true;
> +		sync_needed = true;
> +	}
> +
> +	spin_unlock_irqrestore(&cvc->vc.lock, vc_flags);
> +	spin_unlock_irqrestore(&cvc->pc->lock, pc_flags);
> +
> +	/* waiting for the completion of this VC */
> +	if (sync_needed)
> +		wait_for_completion(&cvc->issue_completion);
> +
> +	/* free all descriptors in list desc_completed */
> +	vchan_synchronize(&cvc->vc);
> +
> +	WARN_ONCE(!list_empty(&cvc->vc.desc_completed),
> +		  "Desc pending still in list desc_completed\n");
> +}
> +
> +static int mtk_cqdma_terminate_all(struct dma_chan *c)
> +{
> +	/* free descriptors not processed yet by hardware */
> +	mtk_cqdma_free_inactive_desc(c);
> +
> +	/* free descriptors being processed by hardware */
> +	mtk_cqdma_free_active_desc(c);
> +
> +	return 0;
> +}
> +
> +static int mtk_cqdma_alloc_chan_resources(struct dma_chan *c)
> +{
> +	struct mtk_cqdma_device *cqdma = to_cqdma_dev(c);
> +	struct mtk_cqdma_vchan *vc = to_cqdma_vchan(c);
> +	struct mtk_cqdma_pchan *pc = NULL;
> +	u32 i, min_refcnt = U32_MAX, refcnt;
> +	unsigned long flags;
> +
> +	/* allocate PC with the minimun refcount */
> +	for (i = 0; i < cqdma->dma_channels; ++i) {
> +		refcnt = refcount_read(&cqdma->pc[i]->refcnt);
> +		if (refcnt < min_refcnt) {
> +			pc = cqdma->pc[i];
> +			min_refcnt = refcnt;
> +		}
> +	}
> +
> +	if (!pc)
> +		return -ENOSPC;
> +
> +	spin_lock_irqsave(&pc->lock, flags);
> +
> +	if (!refcount_read(&pc->refcnt)) {
> +		/* allocate PC when the refcount is zero */
> +		mtk_cqdma_alloc_pchan(pc);
> +		/*
> +		 * refcount_inc would complain increment on 0; use-after-free.
> +		 * Thus, we need to explicitly set it as 1 initially.
> +		 */
> +		refcount_set(&pc->refcnt, 1);
> +	} else {
> +		refcount_inc(&pc->refcnt);
> +	}
> +
> +	spin_unlock_irqrestore(&pc->lock, flags);
> +
> +	vc->pc = pc;
> +
> +	return 0;
> +}
> +
> +static void mtk_cqdma_free_chan_resources(struct dma_chan *c)
> +{
> +	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> +	unsigned long flags;
> +
> +	/* free all descriptors in all lists on the VC */
> +	mtk_cqdma_terminate_all(c);
> +
> +	spin_lock_irqsave(&cvc->pc->lock, flags);
> +
> +	/* PC is not freed until there is no VC mapped to it */
> +	if (refcount_dec_and_test(&cvc->pc->refcnt))
> +		mtk_cqdma_free_pchan(cvc->pc);
> +
> +	spin_unlock_irqrestore(&cvc->pc->lock, flags);
> +}
> +
> +static int mtk_cqdma_hw_init(struct mtk_cqdma_device *cqdma)
> +{
> +	unsigned long flags;
> +	int err;
> +	u32 i;
> +
> +	pm_runtime_enable(cqdma2dev(cqdma));
> +	pm_runtime_get_sync(cqdma2dev(cqdma));
> +
> +	err = clk_prepare_enable(cqdma->clk);
> +
> +	if (err) {
> +		pm_runtime_put_sync(cqdma2dev(cqdma));
> +		pm_runtime_disable(cqdma2dev(cqdma));
> +		return err;
> +	}
> +
> +	/* reset all PCs */
> +	for (i = 0; i < cqdma->dma_channels; ++i) {
> +		spin_lock_irqsave(&cqdma->pc[i]->lock, flags);
> +		if (mtk_cqdma_hard_reset(cqdma->pc[i]) < 0) {
> +			pr_warn("cqdma hard reset timeout\n");
> +			spin_unlock_irqrestore(&cqdma->pc[i]->lock, flags);
> +
> +			clk_disable_unprepare(cqdma->clk);
> +			pm_runtime_put_sync(cqdma2dev(cqdma));
> +			pm_runtime_disable(cqdma2dev(cqdma));
> +			return -EINVAL;
> +		}
> +		spin_unlock_irqrestore(&cqdma->pc[i]->lock, flags);
> +	}
> +
> +	return 0;
> +}
> +
> +static void mtk_cqdma_hw_deinit(struct mtk_cqdma_device *cqdma)
> +{
> +	unsigned long flags;
> +	u32 i;
> +
> +	/* reset all PCs */
> +	for (i = 0; i < cqdma->dma_channels; ++i) {
> +		spin_lock_irqsave(&cqdma->pc[i]->lock, flags);
> +		if (mtk_cqdma_hard_reset(cqdma->pc[i]) < 0)
> +			pr_warn("cqdma hard reset timeout\n");

dev_err

> +		spin_unlock_irqrestore(&cqdma->pc[i]->lock, flags);
> +	}
> +
> +	clk_disable_unprepare(cqdma->clk);
> +
> +	pm_runtime_put_sync(cqdma2dev(cqdma));
> +	pm_runtime_disable(cqdma2dev(cqdma));
> +}
> +
> +static const struct of_device_id mtk_cqdma_match[] = {
> +	{ .compatible = "mediatek,mt6765-cqdma" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mtk_cqdma_match);
> +
> +static int mtk_cqdma_probe(struct platform_device *pdev)
> +{
> +	struct mtk_cqdma_device *cqdma;
> +	struct mtk_cqdma_vchan *vc;
> +	struct dma_device *dd;
> +	struct resource *res;
> +	int err;
> +	u32 i;
> +
> +	cqdma = devm_kzalloc(&pdev->dev, sizeof(*cqdma), GFP_KERNEL);
> +	if (!cqdma)
> +		return -ENOMEM;
> +
> +	dd = &cqdma->ddev;
> +
> +	cqdma->clk = devm_clk_get(&pdev->dev, "cqdma");
> +	if (IS_ERR(cqdma->clk)) {
> +		dev_err(&pdev->dev, "No clock for %s\n",
> +			dev_name(&pdev->dev));
> +		return PTR_ERR(cqdma->clk);
> +	}
> +
> +	dma_cap_set(DMA_MEMCPY, dd->cap_mask);
> +
> +	dd->copy_align = MTK_CQDMA_ALIGN_SIZE;
> +	dd->device_alloc_chan_resources = mtk_cqdma_alloc_chan_resources;
> +	dd->device_free_chan_resources = mtk_cqdma_free_chan_resources;
> +	dd->device_tx_status = mtk_cqdma_tx_status;
> +	dd->device_issue_pending = mtk_cqdma_issue_pending;
> +	dd->device_prep_dma_memcpy = mtk_cqdma_prep_dma_memcpy;
> +	dd->device_terminate_all = mtk_cqdma_terminate_all;
> +	dd->src_addr_widths = MTK_CQDMA_DMA_BUSWIDTHS;
> +	dd->dst_addr_widths = MTK_CQDMA_DMA_BUSWIDTHS;
> +	dd->directions = BIT(DMA_MEM_TO_MEM);
> +	dd->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> +	dd->dev = &pdev->dev;
> +	INIT_LIST_HEAD(&dd->channels);
> +
> +	if (pdev->dev.of_node && of_property_read_u32(pdev->dev.of_node,
> +						      "dma-requests",
> +						      &cqdma->dma_requests)) {
> +		dev_info(&pdev->dev,
> +			 "Using %u as missing dma-requests property\n",
> +			 MTK_CQDMA_NR_VCHANS);
> +
> +		cqdma->dma_requests = MTK_CQDMA_NR_VCHANS;
> +	}
> +
> +	if (pdev->dev.of_node && of_property_read_u32(pdev->dev.of_node,
> +						      "dma-channels",
> +						      &cqdma->dma_channels)) {
> +		dev_info(&pdev->dev,
> +			 "Using %u as missing dma-channels property\n",
> +			 MTK_CQDMA_NR_PCHANS);
> +
> +		cqdma->dma_channels = MTK_CQDMA_NR_PCHANS;
> +	}
> +
> +	cqdma->pc = devm_kcalloc(&pdev->dev, cqdma->dma_channels,
> +				 sizeof(*cqdma->pc), GFP_KERNEL);

what happens when cqdma->dma_channels is more than MTK_CQDMA_NR_PCHANS ?

> +	if (!cqdma->pc)
> +		return -ENOMEM;
> +
> +	/* initialization for PCs */
> +	for (i = 0; i < cqdma->dma_channels; ++i) {
> +		cqdma->pc[i] = devm_kcalloc(&pdev->dev, 1,
> +					    sizeof(**cqdma->pc), GFP_KERNEL);
> +		if (!cqdma->pc[i])
> +			return -ENOMEM;
> +
> +		INIT_LIST_HEAD(&cqdma->pc[i]->queue);
> +		spin_lock_init(&cqdma->pc[i]->lock);
> +		refcount_set(&cqdma->pc[i]->refcnt, 0);
> +
> +		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> +		if (!res) {
> +			dev_err(&pdev->dev, "No mem resource for %s\n",
> +				dev_name(&pdev->dev));
> +			return -EINVAL;
> +		}
> +
> +		cqdma->pc[i]->base = devm_ioremap_resource(&pdev->dev, res);
> +		if (IS_ERR(cqdma->pc[i]->base))
> +			return PTR_ERR(cqdma->pc[i]->base);
> +
> +		/* allocate IRQ resource */
> +		res = platform_get_resource(pdev, IORESOURCE_IRQ, i);
> +		if (!res) {
> +			dev_err(&pdev->dev, "No irq resource for %s\n",
> +				dev_name(&pdev->dev));
> +			return -EINVAL;
> +		}
> +		cqdma->pc[i]->irq = res->start;
> +
> +		err = devm_request_irq(&pdev->dev, cqdma->pc[i]->irq,
> +				       mtk_cqdma_irq, 0, dev_name(&pdev->dev),
> +				       cqdma);
> +		if (err) {
> +			dev_err(&pdev->dev,
> +				"request_irq failed with err %d\n", err);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	/* allocate resource for VCs */
> +	cqdma->vc = devm_kcalloc(&pdev->dev, cqdma->dma_requests,
> +				 sizeof(*cqdma->vc), GFP_KERNEL);
> +	if (!cqdma->vc)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < cqdma->dma_requests; i++) {
> +		vc = &cqdma->vc[i];
> +		vc->vc.desc_free = mtk_cqdma_vdesc_free;
> +		vchan_init(&vc->vc, dd);
> +		init_completion(&vc->issue_completion);
> +	}
> +
> +	err = dma_async_device_register(dd);
> +	if (err)
> +		return err;
> +
> +	err = of_dma_controller_register(pdev->dev.of_node,
> +					 of_dma_xlate_by_chan_id, cqdma);
> +	if (err) {
> +		dev_err(&pdev->dev,
> +			"MediaTek CQDMA OF registration failed %d\n", err);
> +		goto err_unregister;
> +	}
> +
> +	err = mtk_cqdma_hw_init(cqdma);
> +	if (err) {
> +		dev_err(&pdev->dev,
> +			"MediaTek CQDMA HW initialization failed %d\n", err);
> +		goto err_unregister;
> +	}
> +
> +	platform_set_drvdata(pdev, cqdma);
> +
> +	dev_info(&pdev->dev, "MediaTek CQDMA driver registered\n");
> +
> +	return 0;
> +
> +err_unregister:
> +	dma_async_device_unregister(dd);
> +
> +	return err;
> +}
> +
> +static int mtk_cqdma_remove(struct platform_device *pdev)
> +{
> +	struct mtk_cqdma_device *cqdma = platform_get_drvdata(pdev);
> +	struct mtk_cqdma_vchan *vc;
> +	unsigned long flags;
> +	int i;
> +
> +	/* kill VC task */
> +	for (i = 0; i < cqdma->dma_requests; i++) {
> +		vc = &cqdma->vc[i];
> +
> +		list_del(&vc->vc.chan.device_node);
> +		tasklet_kill(&vc->vc.task);
> +	}
> +
> +	/* disable interrupt */
> +	for (i = 0; i < cqdma->dma_channels; i++) {
> +		spin_lock_irqsave(&cqdma->pc[i]->lock, flags);
> +		mtk_dma_clr(cqdma->pc[i], MTK_CQDMA_INT_EN,
> +			    MTK_CQDMA_INT_EN_BIT);
> +		spin_unlock_irqrestore(&cqdma->pc[i]->lock, flags);
> +
> +		/* Waits for any pending IRQ handlers to complete */
> +		synchronize_irq(cqdma->pc[i]->irq);
> +	}
> +
> +	/* disable hardware */
> +	mtk_cqdma_hw_deinit(cqdma);
> +
> +	dma_async_device_unregister(&cqdma->ddev);
> +	of_dma_controller_free(pdev->dev.of_node);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver mtk_cqdma_driver = {
> +	.probe = mtk_cqdma_probe,
> +	.remove = mtk_cqdma_remove,
> +	.driver = {
> +		.name           = KBUILD_MODNAME,
> +		.of_match_table = mtk_cqdma_match,
> +	},
> +};
> +module_platform_driver(mtk_cqdma_driver);
> +
> +MODULE_DESCRIPTION("MediaTek CQDMA Controller Driver");
> +MODULE_AUTHOR("Shun-Chih Yu <shun-chih.yu@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");