linux-kernel - Re: [PATCH] spi: imx: fix the burst length at DMA mode and CPU mode

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Message-ID: <20240131193814.GA12870@francesco-nb>
Date: Wed, 31 Jan 2024 20:38:14 +0100
From: Francesco Dolcini <francesco@...cini.it>
To: carlos.song@....com
Cc: broonie@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
	kernel@...gutronix.de, linux-imx@....com, benjamin@...ler.one,
	stefanmoring@...il.com, linux-spi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: imx: fix the burst length at DMA mode and CPU mode

On Wed, Jan 31, 2024 at 10:46:23AM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
> 
> For DMA mode, the bus width of the DMA is equal to the size of data
> word, so burst length should be configured as bits per word.
> 
> For CPU mode, because of the spi transfer len is in byte, so burst
> length should be configured as bits per byte * spi_imx->count.
> 
> Signed-off-by: Carlos Song <carlos.song@....com>
> Reviewed-by: Clark Wang <xiaoning.wang@....com>
> Fixes: e9b220aeacf1 ("spi: spi-imx: correctly configure burst length when using dma")
> Fixes: 5f66db08cbd3 ("spi: imx: Take in account bits per word instead of assuming 8-bits")

Cc:stable...

> ---
>  drivers/spi/spi-imx.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index 546cdce525fc..b4ade2d53fef 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -54,7 +54,7 @@ MODULE_PARM_DESC(polling_limit_us,
>  #define MX51_ECSPI_CTRL_MAX_BURST	512
>  /* The maximum bytes that IMX53_ECSPI can transfer in target mode.*/
>  #define MX53_MAX_TRANSFER_BYTES		512
> -
> +#define BITS_PER_BYTE	8

this is already defined in linux/bits.h, just use it from there.

Francesco