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mxs: spi: clear XFER_LEN in CTRL0 register during DMA

PATCH New Juha Lumme 2 participants 2 messages Dec 26, 2012

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Arm i.MX and Layerscape SPI
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Juha Lumme

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#0 lore raw

PATCH 1/1 mxs: spi: clear XFER_LEN in CTRL0 register during DMA

On MX23 the XFER_LEN part in CTRL0 register was improperly OR'd, and because of that too many characters were being expected from SPI.
This caused a timeout (SSP_TIMEOUT) to happen in the last package in the DMA chain, and resulted into a corrupted read.
This is a workaround for the problem, by clearing the XFER_LEN bytes always before reading the new size for XFER_LEN.

Cc Marek Vasut <[email protected]>
Cc Fabio Estevam <[email protected]>
Cc Shawn Guo <shawn.guo at linaro.org
Signed-off-by Juha Lumme <[email protected]>
---
 drivers/spi/spi-mxs.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
drivers/spi/spi-mxs.c +4 -1
index 86dd04d..265c33f 100644
@@ -241,6 +241,7 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int cs,
 	INIT_COMPLETION(spi->c);
 
 	ctrl0 = readl(ssp->base + HW_SSP_CTRL0);
+	ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT;
 	ctrl0 |= BM_SSP_CTRL0_DATA_XFER | mxs_spi_cs_to_reg(cs);
 
 	if (*first)

@@ -256,8 +257,10 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int cs,
 		if ((sg_count + 1 == sgs) && *last)
 			ctrl0 |= BM_SSP_CTRL0_IGNORE_CRC;
 
-		if (ssp->devid == IMX23_SSP)
+		if (ssp->devid == IMX23_SSP) {
+			ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT;
 			ctrl0 |= min;
+		}
 
 		dma_xfer[sg_count].pio[0] = ctrl0;
 		dma_xfer[sg_count].pio[3] = min;
Signature · 1 line
1.7.10.4
#1 lore raw

PATCH 1/1 mxs: spi: clear XFER_LEN in CTRL0 register during DMA

Dear Juha Lumme,

Quoted 1 line

On MX23 the XFER_LEN

XFER_COUNT ;-)

Quoted 1 line

part in CTRL0 register was improperly OR'd

... during construction of DMA descriptor chain. Instead of being freshly set.

Quoted 2 lines

, and
because of that too many characters

Bytes

Quoted 1 line

were being expected from SPI.

expected from SPI during the last DMA cycle.

Quoted 1 line

This caused a timeout (SSP_TIMEOUT) to happen in the last package

... during the processing of the last DMA descriptor ...

Quoted 2 lines

in the
DMA chain, and resulted into a corrupted read.

Write too, really ;-)

Quoted 1 line

This is a workaround for the problem

This is actually a correct fix for the issue.

Quoted 2 lines

, by clearing the XFER_LEN bytes always before reading the new size for XFER_LEN.

before setting new XFER_COUNT into the ctrl0 field of DMA control transfer.

Quoted 4 lines
Cc Marek Vasut <[email protected]>
Cc Fabio Estevam <[email protected]>
Cc Shawn Guo <[email protected]
Signed-off-by Juha Lumme <[email protected]>

All but the commit message,

Acked-by Marek Vasut <[email protected]>
Quoted 18 lines
---
 drivers/spi/spi-mxs.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
drivers/spi/spi-mxs.c +1 -0
index 86dd04d..265c33f 100644
@@ -241,6 +241,7 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int
 cs, INIT_COMPLETION(spi->c);
 
 	ctrl0 = readl(ssp->base + HW_SSP_CTRL0);
+	ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT;
 	ctrl0 |= BM_SSP_CTRL0_DATA_XFER | mxs_spi_cs_to_reg(cs);
 
 	if (*first)

@@ -256,8 +257,10 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int
 cs, if ((sg_count + 1 == sgs) && *last)

drivers/spi/spi-mxs.c static int mxs_spi_txrx_dma(struct mxs_spi *spi, int · line 266

Quoted 10 lines
drivers/spi/spi-mxs.c +3 -1
 			ctrl0 |= BM_SSP_CTRL0_IGNORE_CRC;
 
-		if (ssp->devid == IMX23_SSP)
+		if (ssp->devid == IMX23_SSP) {
+			ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT;
 			ctrl0 |= min;
+		}
 
 		dma_xfer[sg_count].pio[0] = ctrl0;
 		dma_xfer[sg_count].pio[3] = min;

Best regards,
Marek Vasut