Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface

Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface

[Sascha Hauer]

On Fri, Jul 13, 2018 at 09:08:46PM +0800, Robin Gong wrote:
> Add MEMCPY capability for imx-sdma driver.
> 
> Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> ---
>  drivers/dma/imx-sdma.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 92 insertions(+), 3 deletions(-)
> 
> @@ -1318,6 +1347,63 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac,
>  	return NULL;
>  }
>  
> +static struct dma_async_tx_descriptor *sdma_prep_memcpy(
> +		struct dma_chan *chan, dma_addr_t dma_dst,
> +		dma_addr_t dma_src, size_t len, unsigned long flags)
> +{
> +	struct sdma_channel *sdmac = to_sdma_chan(chan);
> +	struct sdma_engine *sdma = sdmac->sdma;
> +	int channel = sdmac->channel;
> +	size_t count;
> +	int i = 0, param;
> +	struct sdma_buffer_descriptor *bd;
> +	struct sdma_desc *desc;
> +
> +	if (!chan || !len)
> +		return NULL;
> +
> +	dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu, channel=%d.\n",
> +		&dma_src, &dma_dst, len, channel);
> +
> +	desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM,
> +					len / SDMA_BD_MAX_CNT + 1);
> +	if (!desc)
> +		return NULL;
> +
> +	do {
> +		count = min_t(size_t, len, SDMA_BD_MAX_CNT);
> +		bd = &desc->bd[i];
> +		bd->buffer_addr = dma_src;
> +		bd->ext_buffer_addr = dma_dst;
> +		bd->mode.count = count;
> +		desc->chn_count += count;
> +		/* align with sdma->dma_device.copy_align: 4bytes */
> +		bd->mode.command = 0;
> +
> +		dma_src += count;
> +		dma_dst += count;
> +		len -= count;
> +		i++;

NACK.

Please actually look at your code and find out where you do unaligned DMA
accesses. Hint: What happens when this loop body is executed more than once?

Sascha

> +
> +		param = BD_DONE | BD_EXTD | BD_CONT;
> +		/* last bd */
> +		if (!len) {
> +			param |= BD_INTR;
> +			param |= BD_LAST;
> +			param &= ~BD_CONT;
> +		}
> +
> +		dev_dbg(sdma->dev, "entry %d: count: %zd dma: 0x%x %s%s\n",
> +				i, count, bd->buffer_addr,
> +				param & BD_WRAP ? "wrap" : "",
> +				param & BD_INTR ? " intr" : "");
> +
> +		bd->mode.status = param;
> +	} while (len);
> +

-- 
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[PATCH v2 0/3] add memcpy support for sdma

[Robin Gong]

This patchset is to add memcpy interface for imx-sdma, besides,to
support dmatest and enable config by default, so that could test dma
easily without any other device support such as uart/audio/spi...

Change from v1:
  1. remove bus_width check for memcpy since only max bus width needed for
     memcpy case to speedup copy.
  2. remove DMATEST support patch, since DMATEST is a common memcpy case.
  3. split to single patch for SDMA_BD_MAX_CNT instead of '0xffff'
  4. move sdma_config_ownership() from alloc_chan into sdma_prep_memcpy.
  5. address some minor review comments.

Robin Gong (3):
  dmaengine: imx-sdma: add SDMA_BD_MAX_CNT to replace '0xffff'
  dmaengine: imx-sdma: add memcpy interface
  ARM: configs: imx_v6_v7_defconfig: add DMATEST support

 arch/arm/configs/imx_v6_v7_defconfig |   3 +-
 drivers/dma/imx-sdma.c               | 106 ++++++++++++++++++++++++++++++++---
 2 files changed, 99 insertions(+), 10 deletions(-)

-- 
2.7.4

[PATCH v2 1/3] dmaengine: imx-sdma: add SDMA_BD_MAX_CNT to replace '0xffff'

[Robin Gong]

Add macro SDMA_BD_MAX_CNT to replace '0xffff'.

Signed-off-by: Robin Gong <yibin.gong@nxp.com>
---
 drivers/dma/imx-sdma.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 3b622d6..e3d5e73 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -185,6 +185,7 @@
  * Mode/Count of data node descriptors - IPCv2
  */
 struct sdma_mode_count {
+#define SDMA_BD_MAX_CNT	0xffff
 	u32 count   : 16; /* size of the buffer pointed by this BD */
 	u32 status  :  8; /* E,R,I,C,W,D status bits stored here */
 	u32 command :  8; /* command mostly used for channel 0 */
@@ -1344,9 +1345,9 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
 
 		count = sg_dma_len(sg);
 
-		if (count > 0xffff) {
+		if (count > SDMA_BD_MAX_CNT) {
 			dev_err(sdma->dev, "SDMA channel %d: maximum bytes for sg entry exceeded: %d > %d\n",
-					channel, count, 0xffff);
+					channel, count, SDMA_BD_MAX_CNT);
 			goto err_bd_out;
 		}
 
@@ -1421,9 +1422,9 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic(
 
 	sdmac->flags |= IMX_DMA_SG_LOOP;
 
-	if (period_len > 0xffff) {
+	if (period_len > SDMA_BD_MAX_CNT) {
 		dev_err(sdma->dev, "SDMA channel %d: maximum period size exceeded: %zu > %d\n",
-				channel, period_len, 0xffff);
+				channel, period_len, SDMA_BD_MAX_CNT);
 		goto err_bd_out;
 	}
 
@@ -1970,7 +1971,7 @@ static int sdma_probe(struct platform_device *pdev)
 	sdma->dma_device.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
 	sdma->dma_device.device_issue_pending = sdma_issue_pending;
 	sdma->dma_device.dev->dma_parms = &sdma->dma_parms;
-	dma_set_max_seg_size(sdma->dma_device.dev, 65535);
+	dma_set_max_seg_size(sdma->dma_device.dev, SDMA_BD_MAX_CNT);
 
 	platform_set_drvdata(pdev, sdma);
 
-- 
2.7.4

[PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface

[Robin Gong]

Add MEMCPY capability for imx-sdma driver.

Signed-off-by: Robin Gong <yibin.gong@nxp.com>
---
 drivers/dma/imx-sdma.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 92 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index e3d5e73..ef50f2c 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -342,6 +342,7 @@ struct sdma_desc {
  * @pc_from_device:	script address for those device_2_memory
  * @pc_to_device:	script address for those memory_2_device
  * @device_to_device:	script address for those device_2_device
+ * @pc_to_pc:		script address for those memory_2_memory
  * @flags:		loop mode or not
  * @per_address:	peripheral source or destination address in common case
  *                      destination address in p_2_p case
@@ -367,6 +368,7 @@ struct sdma_channel {
 	enum dma_slave_buswidth		word_size;
 	unsigned int			pc_from_device, pc_to_device;
 	unsigned int			device_to_device;
+	unsigned int                    pc_to_pc;
 	unsigned long			flags;
 	dma_addr_t			per_address, per_address2;
 	unsigned long			event_mask[2];
@@ -869,14 +871,16 @@ static void sdma_get_pc(struct sdma_channel *sdmac,
 	 * These are needed once we start to support transfers between
 	 * two peripherals or memory-to-memory transfers
 	 */
-	int per_2_per = 0;
+	int per_2_per = 0, emi_2_emi = 0;
 
 	sdmac->pc_from_device = 0;
 	sdmac->pc_to_device = 0;
 	sdmac->device_to_device = 0;
+	sdmac->pc_to_pc = 0;
 
 	switch (peripheral_type) {
 	case IMX_DMATYPE_MEMORY:
+		emi_2_emi = sdma->script_addrs->ap_2_ap_addr;
 		break;
 	case IMX_DMATYPE_DSP:
 		emi_2_per = sdma->script_addrs->bp_2_ap_addr;
@@ -949,6 +953,7 @@ static void sdma_get_pc(struct sdma_channel *sdmac,
 	sdmac->pc_from_device = per_2_emi;
 	sdmac->pc_to_device = emi_2_per;
 	sdmac->device_to_device = per_2_per;
+	sdmac->pc_to_pc = emi_2_emi;
 }
 
 static int sdma_load_context(struct sdma_channel *sdmac)
@@ -965,6 +970,8 @@ static int sdma_load_context(struct sdma_channel *sdmac)
 		load_address = sdmac->pc_from_device;
 	else if (sdmac->direction == DMA_DEV_TO_DEV)
 		load_address = sdmac->device_to_device;
+	else if (sdmac->direction == DMA_MEM_TO_MEM)
+		load_address = sdmac->pc_to_pc;
 	else
 		load_address = sdmac->pc_to_device;
 
@@ -1214,10 +1221,28 @@ static int sdma_alloc_chan_resources(struct dma_chan *chan)
 {
 	struct sdma_channel *sdmac = to_sdma_chan(chan);
 	struct imx_dma_data *data = chan->private;
+	struct imx_dma_data mem_data;
 	int prio, ret;
 
-	if (!data)
-		return -EINVAL;
+	/*
+	 * MEMCPY may never setup chan->private by filter function such as
+	 * dmatest, thus create 'struct imx_dma_data mem_data' for this case.
+	 * Please note in any other slave case, you have to setup chan->private
+	 * with 'struct imx_dma_data' in your own filter function if you want to
+	 * request dma channel by dma_request_channel() rather than
+	 * dma_request_slave_channel(). Othwise, 'MEMCPY in case?' will appear
+	 * to warn you to correct your filter function.
+	 */
+	if (!data) {
+		dev_dbg(sdmac->sdma->dev, "MEMCPY in case?\n");
+		mem_data.priority = 2;
+		mem_data.peripheral_type = IMX_DMATYPE_MEMORY;
+		mem_data.dma_request = 0;
+		mem_data.dma_request2 = 0;
+		data = &mem_data;
+
+		sdma_get_pc(sdmac, IMX_DMATYPE_MEMORY);
+	}
 
 	switch (data->priority) {
 	case DMA_PRIO_HIGH:
@@ -1307,6 +1332,10 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac,
 	if (sdma_alloc_bd(desc))
 		goto err_desc_out;
 
+	/* No slave_config called in MEMCPY case, so do here */
+	if (direction == DMA_MEM_TO_MEM)
+		sdma_config_ownership(sdmac, false, true, false);
+
 	if (sdma_load_context(sdmac))
 		goto err_desc_out;
 
@@ -1318,6 +1347,63 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac,
 	return NULL;
 }
 
+static struct dma_async_tx_descriptor *sdma_prep_memcpy(
+		struct dma_chan *chan, dma_addr_t dma_dst,
+		dma_addr_t dma_src, size_t len, unsigned long flags)
+{
+	struct sdma_channel *sdmac = to_sdma_chan(chan);
+	struct sdma_engine *sdma = sdmac->sdma;
+	int channel = sdmac->channel;
+	size_t count;
+	int i = 0, param;
+	struct sdma_buffer_descriptor *bd;
+	struct sdma_desc *desc;
+
+	if (!chan || !len)
+		return NULL;
+
+	dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu, channel=%d.\n",
+		&dma_src, &dma_dst, len, channel);
+
+	desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM,
+					len / SDMA_BD_MAX_CNT + 1);
+	if (!desc)
+		return NULL;
+
+	do {
+		count = min_t(size_t, len, SDMA_BD_MAX_CNT);
+		bd = &desc->bd[i];
+		bd->buffer_addr = dma_src;
+		bd->ext_buffer_addr = dma_dst;
+		bd->mode.count = count;
+		desc->chn_count += count;
+		/* align with sdma->dma_device.copy_align: 4bytes */
+		bd->mode.command = 0;
+
+		dma_src += count;
+		dma_dst += count;
+		len -= count;
+		i++;
+
+		param = BD_DONE | BD_EXTD | BD_CONT;
+		/* last bd */
+		if (!len) {
+			param |= BD_INTR;
+			param |= BD_LAST;
+			param &= ~BD_CONT;
+		}
+
+		dev_dbg(sdma->dev, "entry %d: count: %zd dma: 0x%x %s%s\n",
+				i, count, bd->buffer_addr,
+				param & BD_WRAP ? "wrap" : "",
+				param & BD_INTR ? " intr" : "");
+
+		bd->mode.status = param;
+	} while (len);
+
+	return vchan_tx_prep(&sdmac->vc, &desc->vd, flags);
+}
+
 static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
 		struct dma_chan *chan, struct scatterlist *sgl,
 		unsigned int sg_len, enum dma_transfer_direction direction,
@@ -1903,6 +1989,7 @@ static int sdma_probe(struct platform_device *pdev)
 
 	dma_cap_set(DMA_SLAVE, sdma->dma_device.cap_mask);
 	dma_cap_set(DMA_CYCLIC, sdma->dma_device.cap_mask);
+	dma_cap_set(DMA_MEMCPY, sdma->dma_device.cap_mask);
 
 	INIT_LIST_HEAD(&sdma->dma_device.channels);
 	/* Initialize channel parameters */
@@ -1969,8 +2056,10 @@ static int sdma_probe(struct platform_device *pdev)
 	sdma->dma_device.dst_addr_widths = SDMA_DMA_BUSWIDTHS;
 	sdma->dma_device.directions = SDMA_DMA_DIRECTIONS;
 	sdma->dma_device.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
+	sdma->dma_device.device_prep_dma_memcpy = sdma_prep_memcpy;
 	sdma->dma_device.device_issue_pending = sdma_issue_pending;
 	sdma->dma_device.dev->dma_parms = &sdma->dma_parms;
+	sdma->dma_device.copy_align = DMAENGINE_ALIGN_4_BYTES;
 	dma_set_max_seg_size(sdma->dma_device.dev, SDMA_BD_MAX_CNT);
 
 	platform_set_drvdata(pdev, sdma);
-- 
2.7.4

[PATCH v2 3/3] ARM: configs: imx_v6_v7_defconfig: add DMATEST support

[Robin Gong]

Add DMATEST support and remove invalid options, such as
CONFIG_BT_HCIUART_H4 is default enabled and CONFIG_SND_SOC_IMX_WM8962
is out of date and not appear in any config file. Please refer to
Documentation/driver-api/dmaengine/dmatest.rst to test MEMCPY feature
of imx-sdma.

Signed-off-by: Robin Gong <yibin.gong@nxp.com>
---
 arch/arm/configs/imx_v6_v7_defconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/configs/imx_v6_v7_defconfig b/arch/arm/configs/imx_v6_v7_defconfig
index e381d05..f28d4d9 100644
--- a/arch/arm/configs/imx_v6_v7_defconfig
+++ b/arch/arm/configs/imx_v6_v7_defconfig
@@ -81,7 +81,6 @@ CONFIG_CAN=y
 CONFIG_CAN_FLEXCAN=y
 CONFIG_BT=y
 CONFIG_BT_HCIUART=y
-CONFIG_BT_HCIUART_H4=y
 CONFIG_BT_HCIUART_LL=y
 CONFIG_CFG80211=y
 CONFIG_CFG80211_WEXT=y
@@ -282,7 +281,6 @@ CONFIG_SND_SOC_FSL_ASRC=y
 CONFIG_SND_IMX_SOC=y
 CONFIG_SND_SOC_PHYCORE_AC97=y
 CONFIG_SND_SOC_EUKREA_TLV320=y
-CONFIG_SND_SOC_IMX_WM8962=y
 CONFIG_SND_SOC_IMX_ES8328=y
 CONFIG_SND_SOC_IMX_SGTL5000=y
 CONFIG_SND_SOC_IMX_SPDIF=y
@@ -371,6 +369,7 @@ CONFIG_DMADEVICES=y
 CONFIG_FSL_EDMA=y
 CONFIG_IMX_SDMA=y
 CONFIG_MXS_DMA=y
+CONFIG_DMATEST=m
 CONFIG_STAGING=y
 CONFIG_STAGING_MEDIA=y
 CONFIG_VIDEO_IMX_MEDIA=y
-- 
2.7.4

Re: [PATCH v2 3/3] ARM: configs: imx_v6_v7_defconfig: add DMATEST support

[Shawn Guo]

On Fri, Jul 13, 2018 at 09:08:47PM +0800, Robin Gong wrote:
> Add DMATEST support and remove invalid options, such as
> CONFIG_BT_HCIUART_H4 is default enabled and CONFIG_SND_SOC_IMX_WM8962
> is out of date and not appear in any config file. Please refer to
> Documentation/driver-api/dmaengine/dmatest.rst to test MEMCPY feature
> of imx-sdma.
> 
> Signed-off-by: Robin Gong <yibin.gong@nxp.com>

Applied this one, thanks.

RE: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface

[Robin Gong]

> -----Original Message-----
> From: Sascha Hauer [mailto:s.hauer@pengutronix.de]
> Sent: 2018年7月13日 14:16
> To: Robin Gong <yibin.gong@nxp.com>
> Cc: vkoul@kernel.org; dan.j.williams@intel.com; shawnguo@kernel.org; Fabio
> Estevam <fabio.estevam@nxp.com>; linux@armlinux.org.uk;
> linux-arm-kernel@lists.infradead.org; kernel@pengutronix.de;
> dmaengine@vger.kernel.org; linux-kernel@vger.kernel.org; dl-linux-imx
> <linux-imx@nxp.com>
> Subject: Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface
> 
> On Fri, Jul 13, 2018 at 09:08:46PM +0800, Robin Gong wrote:
> > Add MEMCPY capability for imx-sdma driver.
> >
> > Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> > ---
> >  drivers/dma/imx-sdma.c | 95
> > ++++++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 92 insertions(+), 3 deletions(-)
> >
> > @@ -1318,6 +1347,63 @@ static struct sdma_desc
> *sdma_transfer_init(struct sdma_channel *sdmac,
> >  	return NULL;
> >  }
> >
> > +static struct dma_async_tx_descriptor *sdma_prep_memcpy(
> > +		struct dma_chan *chan, dma_addr_t dma_dst,
> > +		dma_addr_t dma_src, size_t len, unsigned long flags) {
> > +	struct sdma_channel *sdmac = to_sdma_chan(chan);
> > +	struct sdma_engine *sdma = sdmac->sdma;
> > +	int channel = sdmac->channel;
> > +	size_t count;
> > +	int i = 0, param;
> > +	struct sdma_buffer_descriptor *bd;
> > +	struct sdma_desc *desc;
> > +
> > +	if (!chan || !len)
> > +		return NULL;
> > +
> > +	dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu, channel=%d.\n",
> > +		&dma_src, &dma_dst, len, channel);
> > +
> > +	desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM,
> > +					len / SDMA_BD_MAX_CNT + 1);
> > +	if (!desc)
> > +		return NULL;
> > +
> > +	do {
> > +		count = min_t(size_t, len, SDMA_BD_MAX_CNT);
> > +		bd = &desc->bd[i];
> > +		bd->buffer_addr = dma_src;
> > +		bd->ext_buffer_addr = dma_dst;
> > +		bd->mode.count = count;
> > +		desc->chn_count += count;
> > +		/* align with sdma->dma_device.copy_align: 4bytes */
> > +		bd->mode.command = 0;
> > +
> > +		dma_src += count;
> > +		dma_dst += count;
> > +		len -= count;
> > +		i++;
> 
> NACK.
> 
> Please actually look at your code and find out where you do unaligned DMA
> accesses. Hint: What happens when this loop body is executed more than
> once?
> 
> Sascha
Actually internal sdma script has already take such 'align' matter like below:
Burst with words if source/dest address and data length are all aligned with words, burst with
Byte if not. So I will remove the comment '/* align with sdma->dma_device.copy_align: 4bytes */'
In v3. Besides, I have found another bug which introduced by my virt-dma patch. Will send
V3 later.
> 
> > +
> > +		param = BD_DONE | BD_EXTD | BD_CONT;
> > +		/* last bd */
> > +		if (!len) {
> > +			param |= BD_INTR;
> > +			param |= BD_LAST;
> > +			param &= ~BD_CONT;
> > +		}
> > +
> > +		dev_dbg(sdma->dev, "entry %d: count: %zd dma: 0x%x %s%s\n",
> > +				i, count, bd->buffer_addr,
> > +				param & BD_WRAP ? "wrap" : "",
> > +				param & BD_INTR ? " intr" : "");
> > +
> > +		bd->mode.status = param;
> > +	} while (len);
> > +
> 
> --
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> Amtsgericht Hildesheim, HRA 2686           | Fax:
> +49-5121-206917-5555 |

Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface

[Sascha Hauer]

On Fri, Jul 20, 2018 at 09:40:51AM +0000, Robin Gong wrote:
> > -----Original Message-----
> > From: Sascha Hauer [mailto:s.hauer@pengutronix.de]
> > Sent: 2018年7月13日 14:16
> > To: Robin Gong <yibin.gong@nxp.com>
> > Cc: vkoul@kernel.org; dan.j.williams@intel.com; shawnguo@kernel.org; Fabio
> > Estevam <fabio.estevam@nxp.com>; linux@armlinux.org.uk;
> > linux-arm-kernel@lists.infradead.org; kernel@pengutronix.de;
> > dmaengine@vger.kernel.org; linux-kernel@vger.kernel.org; dl-linux-imx
> > <linux-imx@nxp.com>
> > Subject: Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface
> > 
> > On Fri, Jul 13, 2018 at 09:08:46PM +0800, Robin Gong wrote:
> > > Add MEMCPY capability for imx-sdma driver.
> > >
> > > Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> > > ---
> > >  drivers/dma/imx-sdma.c | 95
> > > ++++++++++++++++++++++++++++++++++++++++++++++++--
> > >  1 file changed, 92 insertions(+), 3 deletions(-)
> > >
> > > @@ -1318,6 +1347,63 @@ static struct sdma_desc
> > *sdma_transfer_init(struct sdma_channel *sdmac,
> > >  	return NULL;
> > >  }
> > >
> > > +static struct dma_async_tx_descriptor *sdma_prep_memcpy(
> > > +		struct dma_chan *chan, dma_addr_t dma_dst,
> > > +		dma_addr_t dma_src, size_t len, unsigned long flags) {
> > > +	struct sdma_channel *sdmac = to_sdma_chan(chan);
> > > +	struct sdma_engine *sdma = sdmac->sdma;
> > > +	int channel = sdmac->channel;
> > > +	size_t count;
> > > +	int i = 0, param;
> > > +	struct sdma_buffer_descriptor *bd;
> > > +	struct sdma_desc *desc;
> > > +
> > > +	if (!chan || !len)
> > > +		return NULL;
> > > +
> > > +	dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu, channel=%d.\n",
> > > +		&dma_src, &dma_dst, len, channel);
> > > +
> > > +	desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM,
> > > +					len / SDMA_BD_MAX_CNT + 1);
> > > +	if (!desc)
> > > +		return NULL;
> > > +
> > > +	do {
> > > +		count = min_t(size_t, len, SDMA_BD_MAX_CNT);
> > > +		bd = &desc->bd[i];
> > > +		bd->buffer_addr = dma_src;
> > > +		bd->ext_buffer_addr = dma_dst;
> > > +		bd->mode.count = count;
> > > +		desc->chn_count += count;
> > > +		/* align with sdma->dma_device.copy_align: 4bytes */
> > > +		bd->mode.command = 0;
> > > +
> > > +		dma_src += count;
> > > +		dma_dst += count;
> > > +		len -= count;
> > > +		i++;
> > 
> > NACK.
> > 
> > Please actually look at your code and find out where you do unaligned DMA
> > accesses. Hint: What happens when this loop body is executed more than
> > once?
> > 
> > Sascha
> Actually internal sdma script has already take such 'align' matter like below:
> Burst with words if source/dest address and data length are all aligned with words, burst with
> Byte if not.

If that's the case why did you add the DMAENGINE_ALIGN_4_BYTES flag in the
first place?

Also, if the SDMA script falls back to byte copy when necessary, doing
so probably has performance impacts, so I wonder why you don't just cut
'count' to something that is four byte aligned.

Sascha

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