From df75470b317b46affbe1f5f8f006b34175be9789 Mon Sep 17 00:00:00 2001 From: Marc Kleine-Budde Date: Tue, 18 Jun 2024 19:34:18 +0200 Subject: [PATCH] spi: spi-imx: imx51: revert burst length calculation back to bits_per_word The patch 15a6af94a277 ("spi: Increase imx51 ecspi burst length based on transfer length") increased the burst length calculation in mx51_ecspi_prepare_transfer() to be based on the transfer length. This breaks HW CS + SPI_CS_WORD support which was added in 6e95b23a5b2d ("spi: imx: Implement support for CS_WORD") and transfers with bits-per-word != 8, 16, 32. SPI_CS_WORD means the CS should be toggled after each word. The implementation in the imx-spi driver relies on the fact that the HW CS is toggled automatically by the controller after each burst length number of bits. Setting the burst length to the number of bits of the _whole_ message breaks this use case. Further the patch 15a6af94a277 ("spi: Increase imx51 ecspi burst length based on transfer length") claims to optimize the transfers. But even without this patch, on modern spi-imx controllers with "dynamic_burst = true" (imx51, imx6 and newer), the transfers are already optimized, i.e. the burst length is dynamically adjusted in spi_imx_push() to avoid the pause between the SPI bursts. This has been confirmed by a scope measurement on an imx6d. Subsequent Patches tried to fix these and other problems: - 5f66db08cbd3 ("spi: imx: Take in account bits per word instead of assuming 8-bits") - e9b220aeacf1 ("spi: spi-imx: correctly configure burst length when using dma") - c712c05e46c8 ("spi: imx: fix the burst length at DMA mode and CPU mode") - cf6d79a0f576 ("spi: spi-imx: fix off-by-one in mx51 CPU mode burst length") but the HW CS + SPI_CS_WORD use case is still broken. To fix the problems revert the burst size calculation in mx51_ecspi_prepare_transfer() back to the original form, before 15a6af94a277 ("spi: Increase imx51 ecspi burst length based on transfer length") was applied. Cc: Stefan Moring Cc: Stefan Bigler Cc: Clark Wang Cc: Carlos Song Cc: Sebastian Reichel Cc: Thorsten Scherer Fixes: 15a6af94a277 ("spi: Increase imx51 ecspi burst length based on transfer length") Fixes: 5f66db08cbd3 ("spi: imx: Take in account bits per word instead of assuming 8-bits") Fixes: e9b220aeacf1 ("spi: spi-imx: correctly configure burst length when using dma") Fixes: c712c05e46c8 ("spi: imx: fix the burst length at DMA mode and CPU mode") Fixes: cf6d79a0f576 ("spi: spi-imx: fix off-by-one in mx51 CPU mode burst length") Link: https://lore.kernel.org/all/20240618-oxpecker-of-ideal-mastery-db59f8-mkl@pengutronix.de Signed-off-by: Marc Kleine-Budde Tested-by: Thorsten Scherer Link: https://msgid.link/r/20240618-spi-imx-fix-bustlength-v1-1-2053dd5fdf87@pengutronix.de Signed-off-by: Mark Brown --- drivers/spi/spi-imx.c | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index f4006c82f867..33164ebdb583 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -660,18 +660,8 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx, ctrl |= (spi_imx->target_burst * 8 - 1) << MX51_ECSPI_CTRL_BL_OFFSET; else { - if (spi_imx->usedma) { - ctrl |= (spi_imx->bits_per_word - 1) - << MX51_ECSPI_CTRL_BL_OFFSET; - } else { - if (spi_imx->count >= MX51_ECSPI_CTRL_MAX_BURST) - 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 - 1) - << MX51_ECSPI_CTRL_BL_OFFSET; - } + ctrl |= (spi_imx->bits_per_word - 1) + << MX51_ECSPI_CTRL_BL_OFFSET; } /* set clock speed */