linux-kernel - Re: spi: imx: Increase imx51 ecspi burst length fails on imx6dl and imx8mm

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Date:   Mon, 27 Nov 2023 10:09:27 +0100
From:   linux@...ler.io
To:     Benjamin Bigler <benjamin@...ler.one>
Cc:     broonie@...nel.org, francesco@...cini.it,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        regressions@...ts.linux.dev, stefan.moring@...hnolution.nl
Subject: Re: spi: imx: Increase imx51 ecspi burst length fails on imx6dl and
 imx8mm

Hi 

Thank you Benjamin for the patch.
I have tested the patch and is works fine.

Best regards
Stefan Bigler

Am 2023-11-26T14:19:56.000+01:00 hat Benjamin Bigler <benjamin@...ler.one> geschrieben:
>  Hi
> 
> I did some debugging and I think the problem is that in this case bits_per_word is 8. So in
> spi_imx_dma_configure the buswidth is set to DMA_SLAVE_BUSWIDTH_1_BYTE. But in
> mx51_ecspi_prepare_transfer the BURST_LENGTH is now set to (spi_imx->count * spi_imx->bits_per_word
> - 1)
> before 15a6af94a2779d5dfb42ee4bfac858ea8e964a3f it was (spi_imx->bits_per_word - 1). Now the spi
> transmits 4 byte per byte except for the first word. I added the following patch and it worked again
> 
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index 498e35c8db2c..f514966e2ada 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -659,11 +659,22 @@ 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->count &gt;= 512)
> -			ctrl |= 0xFFF << MX51_ECSPI_CTRL_BL_OFFSET;
> -		else
> -			ctrl |= (spi_imx->count * spi_imx->bits_per_word - 1)
> +		if (spi_imx->usedma)
> +			ctrl |= (spi_imx->bits_per_word *
> +					 spi_imx_bytes_per_word(
> +						 spi_imx->bits_per_word) -
> +				 1)
>  				<< MX51_ECSPI_CTRL_BL_OFFSET;
> +		else {
> +			if (spi_imx->count &gt;= MX51_ECSPI_CTRL_MAX_BURST)
> +				ctrl |= (MX51_ECSPI_CTRL_MAX_BURST - 1)
> +					<< MX51_ECSPI_CTRL_BL_OFFSET;
> +			else
> +				ctrl |= (spi_imx->count *
> +						 spi_imx->bits_per_word -
> +					 1)
> +					<< MX51_ECSPI_CTRL_BL_OFFSET;
> +		}
>  	}
>  
>  	/* set clock speed */
> 
> Best regards,
Benjamin Bigler