linux-kernel - Re: [PATCH 1/1] spi-mxs: Fix chipselect glitch

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Date: Thu, 1 Feb 2024 16:38:38 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Ralf Schlatterbeck <rsc@...tux.com>
Cc: Mark Brown <broonie@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, NXP Linux Team <linux-imx@....com>, 
	Vinod Koul <vkoul@...nel.org>, Miquel Raynal <miquel.raynal@...tlin.com>, 
	linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] spi-mxs: Fix chipselect glitch

On 01.02.2024 14:15:40, Ralf Schlatterbeck wrote:
> There was a change in the mxs-dma engine that uses a new custom flag.
> The change was not applied to the mxs spi driver.
> This results in chipselect being deasserted too early.
> This fixes the chipselect problem by using the new flag in the mxs-spi
> driver.
> 
> Fixes: ceeeb99cd821 ("dmaengine: mxs: rename custom flag")
> Signed-off-by: Ralf Schlatterbeck <rsc@...tux.com>
> ---
> For oscilloscope screenshots and a verbose explanation see my blog post
> at https://blog.runtux.com/posts/2024/02/01/
> 
>  drivers/spi/spi-mxs.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c
> index 1bf080339b5a..a296050c8bd3 100644
> --- a/drivers/spi/spi-mxs.c
> +++ b/drivers/spi/spi-mxs.c
> @@ -39,6 +39,7 @@
>  #include <linux/spi/spi.h>
>  #include <linux/spi/mxs-spi.h>
>  #include <trace/events/spi.h>
> +#include <linux/dma/mxs-dma.h>
>  
>  #define DRIVER_NAME		"mxs-spi"
>  
> @@ -251,8 +252,9 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi,
>  
>  		desc = dmaengine_prep_slave_sg(ssp->dmach,
>  				&dma_xfer[sg_count].sg, 1,
> -				(flags & TXRX_WRITE) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM,
> -				DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +				(flags & TXRX_WRITE)
> +				? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM,
> +				DMA_PREP_INTERRUPT | MXS_DMA_CTRL_WAIT4END);

nitpick: Please omit the line break change from this patch.

Marc

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