linux-kernel - Re: [PATCH] media: mtk-vpu: Ensure alignment of 8 for DTCM buffer

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Date:   Tue, 20 Jul 2021 14:33:52 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        linux-media@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     kernel@...labora.com, dafna3@...il.com, mchehab@...nel.org,
        tfiga@...omium.org, enric.balletbo@...labora.com,
        minghsiu.tsai@...iatek.com, houlong.wei@...iatek.com,
        andrew-ct.chen@...iatek.com, tiffany.lin@...iatek.com,
        matthias.bgg@...il.com, acourbot@...omium.org, hsinyi@...omium.org,
        eizan@...omium.org
Subject: Re: [PATCH] media: mtk-vpu: Ensure alignment of 8 for DTCM buffer

On 14/07/2021 15:48, Dafna Hirschfeld wrote:
> From: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> 
> When running memcpy_toio:
> memcpy_toio(send_obj->share_buf, buf, len);
> it was found that errors appear if len is not a multiple of 8:
> 
> [58.350841] mtk-mdp 14001000.rdma: processing failed: -22
> 
> This patch ensure copy of a multile of 8 size by calling
> round_up(len, 8) when copying
> 
> Fixes: e6599adfad30 ("media: mtk-vpu: avoid unaligned access to DTCM buffer.")
> Reported-by: Alexandre Courbot <acourbot@...omium.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@...labora.com>
> ---
>  drivers/media/platform/mtk-vpu/mtk_vpu.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.c b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> index ec290dde59cf..b464d8192119 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.c
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> @@ -316,6 +316,7 @@ int vpu_ipi_send(struct platform_device *pdev,
>  {
>  	struct mtk_vpu *vpu = platform_get_drvdata(pdev);
>  	struct share_obj __iomem *send_obj = vpu->send_buf;
> +	unsigned char data[SHARE_BUF_SIZE];
>  	unsigned long timeout;
>  	int ret = 0;
>  
> @@ -349,7 +350,9 @@ int vpu_ipi_send(struct platform_device *pdev,
>  		}
>  	} while (vpu_cfg_readl(vpu, HOST_TO_VPU));
>  
> -	memcpy_toio(send_obj->share_buf, buf, len);
> +	memset(data, 0, sizeof(data));

Hmm, how about:

	memset(data + len, 0, sizeof(data) - len);

> +	memcpy(data, buf, len);
> +	memcpy_toio(send_obj->share_buf, data, round_up(len, 8));
>  	writel(len, &send_obj->len);
>  	writel(id, &send_obj->id);
>  
> 

Also note Enric's reply.

Regards,

	Hans