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[PATCH v5 08/11] spi: imx: allow only WML aligned transfers to use DMA

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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
and RX TAIL events. And RX TAIL event does not work correctly.
This can be easily verified by sending SPI transaction with size modulus
WML(32 in our case) not equal 0.

Also removing change introduced in f6ee9b582d2db652497b73c1f117591dfb6d3a90
since this change only fix usecases with transfer size from 33 to 128 bytes
and does not fix 129 bytes etc.

This is output from transaction with len 138 bytes in loopback mode at 10Mhz:
TX0000: a3 97 a2 55 53 be f1 fc f9 79 6b 52 14 13 e9 e2
TX0010: 2d 51 8e 1f 56 08 57 27 a7 05 d4 d0 52 82 77 75
TX0020: 1b 99 4a ed 58 3d 6a 52 36 d5 24 4a 68 8e ad 95
TX0030: 5f 3c 35 b5 c4 8c dd 6c 11 32 3d e2 b4 b4 59 cf
TX0040: ce 23 3d 27 df a7 f9 96 fc 1e e0 66 2c 0e 7b 8c
TX0050: ca 30 42 8f bc 9f 7b ce d1 b8 b1 87 ec 8a d6 bb
TX0060: 2e 15 63 0e 3c dc a4 3a 7a 06 20 a7 93 1b 34 dd
TX0070: 4c f5 ec 88 96 68 d6 68 a0 09 6f 8e 93 47 c9 41
TX0080: db ac cf 97 89 f3 51 05 79 71

RX0000: a3 97 a2 55 53 be f1 fc f9 79 6b 52 14 13 e9 e2
RX0010: 2d 51 8e 1f 56 08 57 27 a7 05 d4 d0 52 82 77 75
RX0020: 1b 99 4a ed 58 3d 6a 52 36 d5 24 4a 68 8e ad 95
RX0030: 5f 3c 35 00 00 b5 00 00 00 c4 00 00 8c 00 00 dd
RX0040: 6c 11 32 3d e2 b4 b4 59 cf ce 23 3d 27 df a7 f9
RX0050: 96 fc 1e e0 66 2c 0e 7b 8c ca 30 42 8f 1f 1f bc
RX0060: 9f 7b ce d1 b8 b1 87 ec 8a d6 bb 2e 15 63 0e ed
RX0070: ed 3c 58 58 58 dc 3d 3d a4 6a 6a 3a 52 52 7a 36
RX0080: 06 20 a7 93 1b 34 dd 4c f5 ec

Zeros at offset 33 and 34 caused by reading empty RX FIFO which not possible
if DMA RX read was triggered by RX event. This mean DMA was triggered
by RX TAIL event.

Signed-off-by: Anton Bondarenko <anton.bondarenko.sama@gmail.com>
---
 drivers/spi/spi-imx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index fa24637..7a68c62 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -204,8 +204,8 @@ 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->wml * sizeof(u32))
+	if (spi_imx->dma_is_inited && transfer->len > spi_imx->wml &&
+	    (transfer->len % spi_imx->wml) == 0)
 		return true;
 	return false;
 }
-- 
2.6.3

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[PATCH v5 00/11] Improvements for SPI IMX driver for Freescale IMX51, IMX53 and IMX6 Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
  [PATCH v5 06/11] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
    Re: [PATCH v5 06/11] spi: imx: return error from dma channel request Sascha Hauer <s.hauer@pengutronix.de> - 2015-12-07 10:40 +0100
      Re: [PATCH v5 06/11] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-08 00:40 +0100
  [PATCH v5 01/11] spi: imx: terminate RX DMA transaction in case of TX DMA timeout Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
  [PATCH v5 08/11] spi: imx: allow only WML aligned transfers to use DMA Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
    Re: [PATCH v5 08/11] spi: imx: allow only WML aligned transfers to  use DMA Sascha Hauer <s.hauer@pengutronix.de> - 2015-12-07 10:50 +0100
      Re: [PATCH v5 08/11] spi: imx: allow only WML aligned transfers to  use DMA Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-08 01:40 +0100
        Re: [PATCH v5 08/11] spi: imx: allow only WML aligned transfers to  use DMA Sascha Hauer <s.hauer@pengutronix.de> - 2015-12-08 07:10 +0100
  [PATCH v5 07/11] spi: imx: defer spi initialization, if DMA engine is Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
  [PATCH v5 02/11] spi: imx: reorder HW operations enable order to avoid possible RX data loss Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100
  [PATCH v5 10/11] spi: imx: replace fixed timeout with calculated Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-12-05 18:00 +0100

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