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From:   Enric Balletbo Serra <eballetbo@gmail.com>
Date:   Wed, 14 Jul 2021 16:03:56 +0200
Message-ID: <CAFqH_52s0qtPT5SE1BUQrsrwg1XB7hLSExeC-ER5nTggKaeeOA@mail.gmail.com>
Subject: Re: [PATCH] media: mtk-vpu: Ensure alignment of 8 for DTCM buffer
To:     Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Cc:     Linux Media Mailing List <linux-media@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Collabora Kernel ML <kernel@collabora.com>, dafna3@gmail.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Tomasz Figa <tfiga@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Minghsiu Tsai <minghsiu.tsai@mediatek.com>,
        Houlong Wei <houlong.wei@mediatek.com>,
        Andrew-CT Chen <andrew-ct.chen@mediatek.com>,
        Tiffany Lin <tiffany.lin@mediatek.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Alexandre Courbot <acourbot@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Eizan Miyamoto <eizan@chromium.org>
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Hi Dafna,

Thank you for working on this and sending the patch to upstream for
further discussion.

Missatge de Dafna Hirschfeld <dafna.hirschfeld@collabora.com> del dia
dc., 14 de jul. 2021 a les 15:49:
>
> From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>

Sorry to confuse you, but I'm not the author of this patch, my from is
only here because I shared with you that patch that I really picked
from a discussion that took place here:

  https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2251840

It'd be really nice to continue the discussion here and set a proper
fix and understand better the root cause and the fix. The patch really
fixes an issue in mainline for mtk-vcodec driver on the mt8173
devices, I can confirm that without it doesn't work properly.

Waiting for your thoughts,
  Enric

> 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@chromium.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.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));
> +       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);
>
> --
> 2.17.1
>
>
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