linux-kernel - Re: [PATCH v2] spi: imx: fix the burst length at DMA mode and CPU mode

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Message-ID: <20240131194207.GB12870@francesco-nb>
Date: Wed, 31 Jan 2024 20:42:07 +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 v2] spi: imx: fix the burst length at DMA mode and CPU
 mode

On Wed, Jan 31, 2024 at 06:19:16PM +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")
> ---
> Changes for V2:
> - Removed BITS_PER_BYTE defination
> ---
>  drivers/spi/spi-imx.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index 546cdce525fc..0436e7a161ef 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -660,15 +660,14 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx,
>  			<< MX51_ECSPI_CTRL_BL_OFFSET;
>  	else {
>  		if (spi_imx->usedma) {
> -			ctrl |= (spi_imx->bits_per_word *
> -				spi_imx_bytes_per_word(spi_imx->bits_per_word) - 1)
> +			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 - 1)
> +				ctrl |= (MX51_ECSPI_CTRL_MAX_BURST * BITS_PER_BYTE - 1)
>  						<< MX51_ECSPI_CTRL_BL_OFFSET;
>  			else
> -				ctrl |= (spi_imx->count * spi_imx->bits_per_word - 1)
> +				ctrl |= (spi_imx->count * BITS_PER_BYTE - 1)
>  						<< MX51_ECSPI_CTRL_BL_OFFSET;
>  		}
>  	}

Add #include <linux/bits.h> given you are using BITS_PER_BYTE

Francesco