linux-kernel - Re: [PATCH v2] media: imx-jpeg: Leave a blank space before the configuration data

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Message-ID: <20220527102820.GB24226@tom-ThinkPad-T14s-Gen-2i>
Date:   Fri, 27 May 2022 12:28:20 +0200
From:   Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
To:     Ming Qian <ming.qian@....com>
Cc:     mchehab@...nel.org, mirela.rabulea@....nxp.com,
        hverkuil-cisco@...all.nl, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] media: imx-jpeg: Leave a blank space before the
 configuration data

On Fri, May 27, 2022 at 06:24:44PM +0800, Ming Qian wrote:
> There is a hardware bug that it will load
> the first 128 bytes of configuration data twice,
> it will led to some configure error.
> so shift the configuration data 128 bytes,
> and make the first 128 bytes all zero,
> then hardware will load the 128 zero twice,
> and ignore them as garbage.
> then the configuration data can be loaded correctly
> 
> Signed-off-by: Ming Qian <ming.qian@....com>
> Reviewed-by: Mirela Rabulea <mirela.rabulea@....com>
> Reviewed-by: Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
> ---
> v2
> - add some comments about why the 0x80 offset is needed
>  drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> index 734e1b65fbc7..c0fd030d0f19 100644
> --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> @@ -519,6 +519,7 @@ static bool mxc_jpeg_alloc_slot_data(struct mxc_jpeg_dev *jpeg,
>  				     GFP_ATOMIC);
>  	if (!cfg_stm)
>  		goto err;
> +	memset(cfg_stm, 0, MXC_JPEG_MAX_CFG_STREAM);
>  	jpeg->slot_data[slot].cfg_stream_vaddr = cfg_stm;
>  
>  skip_alloc:
> @@ -755,7 +756,13 @@ static unsigned int mxc_jpeg_setup_cfg_stream(void *cfg_stream_vaddr,
>  					      u32 fourcc,
>  					      u16 w, u16 h)
>  {
> -	unsigned int offset = 0;
> +	/*
> +	 * There is a hardware issue that first 128 bytes of configuration data
> +	 * can't be loaded correctly.
> +	 * To avoid this issue, we need to write the configuration from
> +	 * an offset which should be no less than 0x80 (128 bytes).
> +	 */
> +	unsigned int offset = 0x80;
>  	u8 *cfg = (u8 *)cfg_stream_vaddr;
>  	struct mxc_jpeg_sof *sof;
>  	struct mxc_jpeg_sos *sos;
> -- 
> 2.36.1
> 

Looks good to me!

Thanks,
Tommaso

-- 
Tommaso Merciai
Embedded Linux Engineer
tommaso.merciai@...rulasolutions.com
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