[PATCH v3] spi: spi-imx: fix off-by-one in mx51 CPU mode burst length

[PATCH v3] spi: spi-imx: fix off-by-one in mx51 CPU mode burst length

[Adam Butcher]

From: Adam Butcher <adam@jessamine.co.uk>

c712c05e46c8 ("spi: imx: fix the burst length at DMA mode and CPU mode")
corrects three cases of setting the ECSPI burst length but erroneously
leaves the in-range CPU case one bit to big (in that field a value of
0 means 1 bit).  The effect was that transmissions that should have been
8-bit bytes appeared as 9-bit causing failed communication with SPI
devices.

Link: https://lore.kernel.org/all/20240201105451.507005-1-carlos.song@nxp.com/
Link: https://lore.kernel.org/all/20240204091912.36488-1-carlos.song@nxp.com/
Fixes: c712c05e46c8 ("spi: imx: fix the burst length at DMA mode and CPU mode")
Signed-off-by: Adam Butcher <adam@jessamine.co.uk>
---

v2. Cleaned up body text.  No diff change.
v3. Corrected log message ref to upstream commit being fixed.  No diff change.

The original patch submission up to v4 (first link above) did not contain
the bug that this patch fixes.  It was introduced in the v5 update (second
link).

---
 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 7c1fcd5ed52f7..100552e6c56bc 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -743,8 +743,8 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx,
 				ctrl |= (MX51_ECSPI_CTRL_MAX_BURST * BITS_PER_BYTE - 1)
 						<< MX51_ECSPI_CTRL_BL_OFFSET;
 			else
-				ctrl |= spi_imx->count / DIV_ROUND_UP(spi_imx->bits_per_word,
-						BITS_PER_BYTE) * spi_imx->bits_per_word
+				ctrl |= (spi_imx->count / DIV_ROUND_UP(spi_imx->bits_per_word,
+						BITS_PER_BYTE) * spi_imx->bits_per_word - 1)
 						<< MX51_ECSPI_CTRL_BL_OFFSET;
 		}
 	}
-- 
2.43.0

Re: [PATCH v3] spi: spi-imx: fix off-by-one in mx51 CPU mode burst length

[Mark Brown]

On Mon, 18 Mar 2024 17:50:52 +0000, Adam Butcher wrote:
> c712c05e46c8 ("spi: imx: fix the burst length at DMA mode and CPU mode")
> corrects three cases of setting the ECSPI burst length but erroneously
> leaves the in-range CPU case one bit to big (in that field a value of
> 0 means 1 bit).  The effect was that transmissions that should have been
> 8-bit bytes appeared as 9-bit causing failed communication with SPI
> devices.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: spi-imx: fix off-by-one in mx51 CPU mode burst length
      commit: cf6d79a0f5769b5f4d9579ddaf88d2c30b03b873

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark