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Groups > linux.kernel > #1232979 > unrolled thread

[PATCH v2 1/8] spi: imx: Fix DMA transfer

Started byAnton Bondarenko <anton_bondarenko@mentor.com>
First post2015-09-25 20:00 +0200
Last post2015-10-01 02:10 +0200
Articles 3 — 3 participants

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  [PATCH v2 1/8] spi: imx: Fix DMA transfer Anton Bondarenko <anton_bondarenko@mentor.com> - 2015-09-25 20:00 +0200
    Re: [PATCH v2 1/8] spi: imx: Fix DMA transfer kbuild test robot <lkp@intel.com> - 2015-09-28 05:50 +0200
    Re: [PATCH v2 1/8] spi: imx: Fix DMA transfer "Bondarenko, Anton" <Anton_Bondarenko@mentor.com> - 2015-10-01 02:10 +0200

#1232979 — [PATCH v2 1/8] spi: imx: Fix DMA transfer

FromAnton Bondarenko <anton_bondarenko@mentor.com>
Date2015-09-25 20:00 +0200
Subject[PATCH v2 1/8] spi: imx: Fix DMA transfer
Message-ID<qcFrQ-8B-15@gated-at.bofh.it>
RX DMA tail data handling doesn't work correctly in many cases with
current implementation. It happens because SPI core was setup
to generates both RX watermark level and RX DATA TAIL events
incorrectly. SPI transfer triggering for DMA also done in wrong way.

SPI client wants to transfer 70 words for example. The old DMA
implementation setup RX DATA TAIL equal 6 words. In this case
RX DMA event will be generated after 6 words read from RX FIFO.
The garbage can be read out from RX FIFO because SPI HW does
not receive all required words to trigger RX watermark event.

New implementation change handling of RX data tail. DMA is used to process
all TX data and only full chunks of RX data with size aligned to FIFO/2.
Driver is waiting until both TX and RX DMA transaction done and all
TX data are pushed out. At that moment there is only RX data tail in
the RX FIFO. This data read out using PIO.

Transfer triggering changed to avoid RX data loss.

Signed-off-by: Anton Bondarenko <anton_bondarenko@mentor.com>
---
 drivers/spi/spi-imx.c | 105 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 66 insertions(+), 39 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index f9deb84..165bc2c 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -39,6 +39,8 @@
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>
 
+#include <asm/cacheflush.h>
+
 #include <linux/platform_data/dma-imx.h>
 #include <linux/platform_data/spi-imx.h>
 
@@ -53,6 +55,7 @@
 /* generic defines to abstract from the different register layouts */
 #define MXC_INT_RR	(1 << 0) /* Receive data ready interrupt */
 #define MXC_INT_TE	(1 << 1) /* Transmit FIFO empty interrupt */
+#define MXC_INT_TCEN	BIT(7)   /* Transfer complete */
 
 /* The maximum  bytes that a sdma BD can transfer.*/
 #define MAX_SDMA_BD_BYTES  (1 << 15)
@@ -104,9 +107,7 @@ struct spi_imx_data {
 	unsigned int dma_is_inited;
 	unsigned int dma_finished;
 	bool usedma;
-	u32 rx_wml;
-	u32 tx_wml;
-	u32 rxt_wml;
+	u32 wml;
 	struct completion dma_rx_completion;
 	struct completion dma_tx_completion;
 
@@ -201,9 +202,8 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 {
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
 
-	if (spi_imx->dma_is_inited
-	    && transfer->len > spi_imx->rx_wml * sizeof(u32)
-	    && transfer->len > spi_imx->tx_wml * sizeof(u32))
+	if (spi_imx->dma_is_inited &&
+	    (transfer->len > spi_imx->wml * sizeof(u32)))
 		return true;
 	return false;
 }
@@ -228,6 +228,7 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 #define MX51_ECSPI_INT		0x10
 #define MX51_ECSPI_INT_TEEN		(1 <<  0)
 #define MX51_ECSPI_INT_RREN		(1 <<  3)
+#define MX51_ECSPI_INT_TCEN		BIT(7)
 
 #define MX51_ECSPI_DMA      0x14
 #define MX51_ECSPI_DMA_TX_WML_OFFSET	0
@@ -292,6 +293,9 @@ static void __maybe_unused mx51_ecspi_intctrl(struct spi_imx_data *spi_imx, int
 	if (enable & MXC_INT_RR)
 		val |= MX51_ECSPI_INT_RREN;
 
+	if (enable & MXC_INT_TCEN)
+		val |= MX51_ECSPI_INT_TCEN;
+
 	writel(val, spi_imx->base + MX51_ECSPI_INT);
 }
 
@@ -311,8 +315,9 @@ static void __maybe_unused mx51_ecspi_trigger(struct spi_imx_data *spi_imx)
 static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
 		struct spi_imx_config *config)
 {
-	u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0, dma = 0;
-	u32 tx_wml_cfg, rx_wml_cfg, rxt_wml_cfg;
+	u32 ctrl = MX51_ECSPI_CTRL_ENABLE, dma = 0;
+	u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
+
 	u32 clk = config->speed_hz, delay;
 
 	/*
@@ -369,19 +374,10 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
 	 * and enable DMA request.
 	 */
 	if (spi_imx->dma_is_inited) {
-		dma = readl(spi_imx->base + MX51_ECSPI_DMA);
-
-		spi_imx->rxt_wml = spi_imx_get_fifosize(spi_imx) / 2;
-		rx_wml_cfg = spi_imx->rx_wml << MX51_ECSPI_DMA_RX_WML_OFFSET;
-		tx_wml_cfg = spi_imx->tx_wml << MX51_ECSPI_DMA_TX_WML_OFFSET;
-		rxt_wml_cfg = spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET;
-		dma = (dma & ~MX51_ECSPI_DMA_TX_WML_MASK
-			   & ~MX51_ECSPI_DMA_RX_WML_MASK
-			   & ~MX51_ECSPI_DMA_RXT_WML_MASK)
-			   | rx_wml_cfg | tx_wml_cfg | rxt_wml_cfg
-			   |(1 << MX51_ECSPI_DMA_TEDEN_OFFSET)
-			   |(1 << MX51_ECSPI_DMA_RXDEN_OFFSET)
-			   |(1 << MX51_ECSPI_DMA_RXTDEN_OFFSET);
+		dma = (spi_imx->wml - 1) << MX51_ECSPI_DMA_RX_WML_OFFSET
+		      | (spi_imx->wml - 1) << MX51_ECSPI_DMA_TX_WML_OFFSET
+		      | (1 << MX51_ECSPI_DMA_TEDEN_OFFSET)
+		      | (1 << MX51_ECSPI_DMA_RXDEN_OFFSET);
 
 		writel(dma, spi_imx->base + MX51_ECSPI_DMA);
 	}
@@ -825,6 +821,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
 	if (of_machine_is_compatible("fsl,imx6dl"))
 		return 0;
 
+	spi_imx->wml = spi_imx_get_fifosize(spi_imx) / 2;
+
 	/* Prepare for TX DMA: */
 	master->dma_tx = dma_request_slave_channel(dev, "tx");
 	if (!master->dma_tx) {
@@ -836,7 +834,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
 	slave_config.direction = DMA_MEM_TO_DEV;
 	slave_config.dst_addr = res->start + MXC_CSPITXDATA;
 	slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
-	slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
+	slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx)
+					- spi_imx->wml;
 	ret = dmaengine_slave_config(master->dma_tx, &slave_config);
 	if (ret) {
 		dev_err(dev, "error in TX dma configuration.\n");
@@ -854,7 +853,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
 	slave_config.direction = DMA_DEV_TO_MEM;
 	slave_config.src_addr = res->start + MXC_CSPIRXDATA;
 	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
-	slave_config.src_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
+	slave_config.src_maxburst = spi_imx_get_fifosize(spi_imx)
+					- spi_imx->wml;
 	ret = dmaengine_slave_config(master->dma_rx, &slave_config);
 	if (ret) {
 		dev_err(dev, "error in RX dma configuration.\n");
@@ -867,8 +867,6 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
 	master->max_dma_len = MAX_SDMA_BD_BYTES;
 	spi_imx->bitbang.master->flags = SPI_MASTER_MUST_RX |
 					 SPI_MASTER_MUST_TX;
-	spi_imx->tx_wml = spi_imx_get_fifosize(spi_imx) / 2;
-	spi_imx->rx_wml = spi_imx_get_fifosize(spi_imx) / 2;
 	spi_imx->dma_is_inited = 1;
 
 	return 0;
@@ -897,8 +895,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 	struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
 	int ret;
 	unsigned long timeout;
-	u32 dma;
-	int left;
+	const int left = transfer->len % spi_imx->wml;
 	struct spi_master *master = spi_imx->bitbang.master;
 	struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;
 
@@ -915,9 +912,23 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 	}
 
 	if (rx) {
+		/* Cut RX data tail */
+		const unsigned int old_nents = rx->nents;
+
+		WARN_ON(sg_dma_len(&rx->sgl[rx->nents - 1]) < left);
+		sg_dma_len(&rx->sgl[rx->nents - 1]) -= left;
+		if (sg_dma_len(&rx->sgl[rx->nents - 1]) == 0)
+			--rx->nents;
+
 		desc_rx = dmaengine_prep_slave_sg(master->dma_rx,
 					rx->sgl, rx->nents, DMA_DEV_TO_MEM,
 					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+
+		/* Restore old SG table state */
+		if (old_nents > rx->nents)
+			++rx->nents;
+		sg_dma_len(&rx->sgl[rx->nents - 1]) += left;
+
 		if (!desc_rx)
 			goto no_dma;
 
@@ -932,17 +943,10 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 	/* Trigger the cspi module. */
 	spi_imx->dma_finished = 0;
 
-	dma = readl(spi_imx->base + MX51_ECSPI_DMA);
-	dma = dma & (~MX51_ECSPI_DMA_RXT_WML_MASK);
-	/* Change RX_DMA_LENGTH trigger dma fetch tail data */
-	left = transfer->len % spi_imx->rxt_wml;
-	if (left)
-		writel(dma | (left << MX51_ECSPI_DMA_RXT_WML_OFFSET),
-				spi_imx->base + MX51_ECSPI_DMA);
+	dma_async_issue_pending(master->dma_rx);
+	dma_async_issue_pending(master->dma_tx);
 	spi_imx->devtype_data->trigger(spi_imx);
 
-	dma_async_issue_pending(master->dma_tx);
-	dma_async_issue_pending(master->dma_rx);
 	/* Wait SDMA to finish the data transfer.*/
 	timeout = wait_for_completion_timeout(&spi_imx->dma_tx_completion,
 						IMX_DMA_TIMEOUT);
@@ -951,6 +955,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 			dev_driver_string(&master->dev),
 			dev_name(&master->dev));
 		dmaengine_terminate_all(master->dma_tx);
+		dmaengine_terminate_all(master->dma_rx);
 	} else {
 		timeout = wait_for_completion_timeout(
 				&spi_imx->dma_rx_completion, IMX_DMA_TIMEOUT);
@@ -960,10 +965,32 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 				dev_name(&master->dev));
 			spi_imx->devtype_data->reset(spi_imx);
 			dmaengine_terminate_all(master->dma_rx);
+		} else if (left) {
+			void *pio_buffer = transfer->rx_buf
+						+ (transfer->len - left);
+
+			dma_sync_sg_for_cpu(master->dma_rx->device->dev,
+					    rx->sgl, rx->nents,
+					    DMA_FROM_DEVICE);
+
+			spi_imx->rx_buf = pio_buffer;
+			spi_imx->txfifo = left;
+			reinit_completion(&spi_imx->xfer_done);
+
+			spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TCEN);
+
+			timeout = wait_for_completion_timeout(
+					&spi_imx->xfer_done, IMX_DMA_TIMEOUT);
+			if (!timeout) {
+				pr_warn("%s %s: I/O Error in RX tail\n",
+					dev_driver_string(&master->dev),
+					dev_name(&master->dev));
+			}
+
+			dmac_flush_range(pio_buffer, pio_buffer + left);
+			outer_flush_range(virt_to_phys(pio_buffer),
+					  virt_to_phys(pio_buffer) + left);
 		}
-		writel(dma |
-		       spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET,
-		       spi_imx->base + MX51_ECSPI_DMA);
 	}
 
 	spi_imx->dma_finished = 1;
-- 
2.5.2

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#1233832

Fromkbuild test robot <lkp@intel.com>
Date2015-09-28 05:50 +0200
Message-ID<qdxBT-2kC-1@gated-at.bofh.it>
In reply to#1232979

[Multipart message — attachments visible in raw view] — view raw

Hi Anton,

[auto build test results on v4.3-rc2 -- if it's inappropriate base, please ignore]

config: arm-arm5 (attached as .config)
reproduce:
  wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
  chmod +x ~/bin/make.cross
  git checkout 82f1264caef01600e640af28b9f92d5a86efd25b
  # save the attached .config to linux build tree
  make.cross ARCH=arm 

All error/warnings (new ones prefixed by >>):

>> ERROR: "arm926_dma_flush_range" [drivers/spi/spi-imx.ko] undefined!

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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#1236863

From"Bondarenko, Anton" <Anton_Bondarenko@mentor.com>
Date2015-10-01 02:10 +0200
Message-ID<qezBD-3SU-5@gated-at.bofh.it>
In reply to#1232979
>> @@ -201,9 +202,8 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
>>  {
>>  	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
>>  
>> -	if (spi_imx->dma_is_inited
>> -	    && transfer->len > spi_imx->rx_wml * sizeof(u32)
>> -	    && transfer->len > spi_imx->tx_wml * sizeof(u32))
>> +	if (spi_imx->dma_is_inited &&
>> +	    (transfer->len > spi_imx->wml * sizeof(u32)))
> Add Sascha in the loop. I don't think "* sizeof(u32)", since even 1 byte data
> will consume one position of 32bit FIFO Thus if here
> spi_imx->wml = spi_imx_get_fifosize(spi_imx) / 2 = 32, the threshold value
> which judge DMA mode used or not should be 32 not 32 * 4.
> Of course, it will not cause any function break since both DMA and PIO can work
> ,but I think we'd better correct it.
I agree, in case of 1 byte SPI word we do not need to multiply by 4.
But for 16 bit and 32 bit SPI words it's necessary. This part is
addressed in patch 3.
I could remove "* sizeof(u32)" for now.
>>  		return true;
>>  	return false;
>>  }
>> @@ -369,19 +374,10 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>>  	 * and enable DMA request.
>>  	 */
>>  	if (spi_imx->dma_is_inited) {
>> -		dma = readl(spi_imx->base + MX51_ECSPI_DMA);
>> -
>> -		spi_imx->rxt_wml = spi_imx_get_fifosize(spi_imx) / 2;
>> -		rx_wml_cfg = spi_imx->rx_wml << MX51_ECSPI_DMA_RX_WML_OFFSET;
>> -		tx_wml_cfg = spi_imx->tx_wml << MX51_ECSPI_DMA_TX_WML_OFFSET;
>> -		rxt_wml_cfg = spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET;
>> -		dma = (dma & ~MX51_ECSPI_DMA_TX_WML_MASK
>> -			   & ~MX51_ECSPI_DMA_RX_WML_MASK
>> -			   & ~MX51_ECSPI_DMA_RXT_WML_MASK)
>> -			   | rx_wml_cfg | tx_wml_cfg | rxt_wml_cfg
>> -			   |(1 << MX51_ECSPI_DMA_TEDEN_OFFSET)
>> -			   |(1 << MX51_ECSPI_DMA_RXDEN_OFFSET)
>> -			   |(1 << MX51_ECSPI_DMA_RXTDEN_OFFSET);
>> +		dma = (spi_imx->wml - 1) << MX51_ECSPI_DMA_RX_WML_OFFSET
>> +		      | (spi_imx->wml - 1) << MX51_ECSPI_DMA_TX_WML_OFFSET
>> +		      | (1 << MX51_ECSPI_DMA_TEDEN_OFFSET)
>> +		      | (1 << MX51_ECSPI_DMA_RXDEN_OFFSET);
> Please set tx threshold as 0 as your v1 patch if I remember right, as our
> internal tree done:
> http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/commit/drivers/spi/spi-imx.c?h=imx_3.14.28_7d_alpha&id=2e7615e2f399e39c58dd31f84a31f7c2592da7e7
Will be fixed in V3 patchset
>>  
>>  		writel(dma, spi_imx->base + MX51_ECSPI_DMA);
>>  	}
>> @@ -825,6 +821,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
>>  	if (of_machine_is_compatible("fsl,imx6dl"))
>>  		return 0;
>>  
>> +	spi_imx->wml = spi_imx_get_fifosize(spi_imx) / 2;
>> +
>>  	/* Prepare for TX DMA: */
>>  	master->dma_tx = dma_request_slave_channel(dev, "tx");
>>  	if (!master->dma_tx) {
>> @@ -836,7 +834,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
>>  	slave_config.direction = DMA_MEM_TO_DEV;
>>  	slave_config.dst_addr = res->start + MXC_CSPITXDATA;
>>  	slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>> -	slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
>> +	slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx)
>> +					- spi_imx->wml;
> slave_config.dst_maxburst = spi_imx->wml;?
Will be fixed in V3
>>  	ret = dmaengine_slave_config(master->dma_tx, &slave_config);
>>  	if (ret) {
>>  		dev_err(dev, "error in TX dma configuration.\n");
>> @@ -854,7 +853,8 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
>>  	slave_config.direction = DMA_DEV_TO_MEM;
>>  	slave_config.src_addr = res->start + MXC_CSPIRXDATA;
>>  	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>> -	slave_config.src_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
>> +	slave_config.src_maxburst = spi_imx_get_fifosize(spi_imx)
>> +					- spi_imx->wml;
> slave_config.src_maxburst = spi_imx->wml;?
Will be fixed in V3
>>  	ret = dmaengine_slave_config(master->dma_rx, &slave_config);
>>  	if (ret) {
>>  		dev_err(dev, "error in RX dma configuration.\n");
>> @@ -867,8 +867,6 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
>>  	master->max_dma_len = MAX_SDMA_BD_BYTES;
>>  	spi_imx->bitbang.master->flags = SPI_MASTER_MUST_RX |
>>  					 SPI_MASTER_MUST_TX;
>> -	spi_imx->tx_wml = spi_imx_get_fifosize(spi_imx) / 2;
>> -	spi_imx->rx_wml = spi_imx_get_fifosize(spi_imx) / 2;
>>  	spi_imx->dma_is_inited = 1;
>>  
>>  	return 0;
>> @@ -897,8 +895,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>>  	struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
>>  	int ret;
>>  	unsigned long timeout;
>> -	u32 dma;
>> -	int left;
>> +	const int left = transfer->len % spi_imx->wml;
>>  	struct spi_master *master = spi_imx->bitbang.master;
>>  	struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;
>>  
>> @@ -915,9 +912,23 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>>  	}
>>  
>>  	if (rx) {
>> +		/* Cut RX data tail */
>> +		const unsigned int old_nents = rx->nents;
>> +
>> +		WARN_ON(sg_dma_len(&rx->sgl[rx->nents - 1]) < left);
>> +		sg_dma_len(&rx->sgl[rx->nents - 1]) -= left;
>> +		if (sg_dma_len(&rx->sgl[rx->nents - 1]) == 0)
>> +			--rx->nents;
>> +
>>  		desc_rx = dmaengine_prep_slave_sg(master->dma_rx,
>>  					rx->sgl, rx->nents, DMA_DEV_TO_MEM,
>>  					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>> +
>> +		/* Restore old SG table state */
>> +		if (old_nents > rx->nents)
>> +			++rx->nents;
>> +		sg_dma_len(&rx->sgl[rx->nents - 1]) += left;
>> +
>>  		if (!desc_rx)
>>  			goto no_dma;
>>  
>> @@ -932,17 +943,10 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>>  	/* Trigger the cspi module. */
>>  	spi_imx->dma_finished = 0;
>>  
>> -	dma = readl(spi_imx->base + MX51_ECSPI_DMA);
>> -	dma = dma & (~MX51_ECSPI_DMA_RXT_WML_MASK);
>> -	/* Change RX_DMA_LENGTH trigger dma fetch tail data */
>> -	left = transfer->len % spi_imx->rxt_wml;
>> -	if (left)
>> -		writel(dma | (left << MX51_ECSPI_DMA_RXT_WML_OFFSET),
>> -				spi_imx->base + MX51_ECSPI_DMA);
>> +	dma_async_issue_pending(master->dma_rx);
>> +	dma_async_issue_pending(master->dma_tx);
>>  	spi_imx->devtype_data->trigger(spi_imx);
>>  
>> -	dma_async_issue_pending(master->dma_tx);
>> -	dma_async_issue_pending(master->dma_rx);
> why change the sequence of issue_pending and trigger? I don't think need to do so.
The reason for order change for TX/RX requests is avoiding buffer
overflow for RX. This will happen if our code will be interrupted after
SPI HW and TX DMA started. This mean we will sent TX data, but there is
no one to consume RX data. So RX DMA should start before TX DMA.
On other hand TX DMA should start work earlier to fill buffer before SPI
HW starts pushing data out. This will give us a small performance bonus.
Not a big one, but still something for free.
>>  	/* Wait SDMA to finish the data transfer.*/
>>  	timeout = wait_for_completion_timeout(&spi_imx->dma_tx_completion,
>>  						IMX_DMA_TIMEOUT);
>> @@ -951,6 +955,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>>  			dev_driver_string(&master->dev),
>>  			dev_name(&master->dev));
>>  		dmaengine_terminate_all(master->dma_tx);
>> +		dmaengine_terminate_all(master->dma_rx);
>>  	} else {
>>  		timeout = wait_for_completion_timeout(
>>  				&spi_imx->dma_rx_completion, IMX_DMA_TIMEOUT);
>> @@ -960,10 +965,32 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>>  				dev_name(&master->dev));
>>  			spi_imx->devtype_data->reset(spi_imx);
>>  			dmaengine_terminate_all(master->dma_rx);
>> +		} else if (left) {
>> +			void *pio_buffer = transfer->rx_buf
>> +						+ (transfer->len - left);
>> +
>> +			dma_sync_sg_for_cpu(master->dma_rx->device->dev,
>> +					    rx->sgl, rx->nents,
>> +					    DMA_FROM_DEVICE);
> Only the last entry needed:
> dma_sync_sg_for_cpu(master->dma_rx->device->dev,
> 			rx->sgl[rx->nents - 1], 1,
> 			DMA_FROM_DEVICE);
Agree. Will be fixed in V3
>> +
>> +			spi_imx->rx_buf = pio_buffer;
>> +			spi_imx->txfifo = left;
>> +			reinit_completion(&spi_imx->xfer_done);
>> +
>> +			spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TCEN);
>> +
>> +			timeout = wait_for_completion_timeout(
>> +					&spi_imx->xfer_done, IMX_DMA_TIMEOUT);
>> +			if (!timeout) {
>> +				pr_warn("%s %s: I/O Error in RX tail\n",
>> +					dev_driver_string(&master->dev),
>> +					dev_name(&master->dev));
>> +			}
>> +
>> +			dmac_flush_range(pio_buffer, pio_buffer + left);
The line above causing build error in some configurations. Replacing it
with dma_sync_sg call similar to previous one, but with
>> +			outer_flush_range(virt_to_phys(pio_buffer),
>> +					  virt_to_phys(pio_buffer) + left);
>>  		}
>> -		writel(dma |
>> -		       spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET,
>> -		       spi_imx->base + MX51_ECSPI_DMA);
>>  	}
>>  
>>  	spi_imx->dma_finished = 1;
>> -- 
>> 2.5.2
>>

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