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Date:   Thu, 30 Jul 2020 17:29:25 +0200
From:   Sam Ravnborg <sam@ravnborg.org>
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        od@zcrc.me, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/3] drm/ingenic: ipu: Remove YUV422 from supported
 formats on JZ4725B
Message-ID: <20200730152925.GA1474381@ravnborg.org>
References: <20200730144830.10479-1-paul@crapouillou.net>
 <20200730144830.10479-3-paul@crapouillou.net>
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Hi Paul

On Thu, Jul 30, 2020 at 04:48:29PM +0200, Paul Cercueil wrote:
> When configuring the IPU for packed YUV 4:2:2, depending on the scaling
> ratios given by the source and destination resolutions, it is possible
> to crash the IPU block, to the point where a software reset of the IP
> does not fix it. This can happen anytime, in the first few frames, or
> after dozens of minutes. The same crash also happens when the IPU is
> fully controlled by the LCD controller (in that case no HW register is
> written at any moment after startup), which points towards a hardware
> bug.
> 
> Thanksfully multiplanar YUV is not affected.
> 
> Until this bug is fixed or worked around, address this issue by removing
> support for YUV 4:2:2 on the IPU of the JZ4725B.
> 
> v2: Update commit message (remove the "crash beyond repair" bit)
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>  drivers/gpu/drm/ingenic/ingenic-ipu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-ipu.c b/drivers/gpu/drm/ingenic/ingenic-ipu.c
> index 7eae56fa92ea..7dd2a6ae4994 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-ipu.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-ipu.c
> @@ -795,10 +795,16 @@ static int ingenic_ipu_remove(struct platform_device *pdev)
>  }
>  
>  static const u32 jz4725b_ipu_formats[] = {
> +	/*
> +	 * While officially supported, packed YUV 4:2:2 formats can cause
> +	 * random hardware crashes on JZ4725B under certain circumstances.
> +	 * It seems to happen with some specific resize ratios.
> +	 * Until a proper workaround or fix is found, disable these formats.
>  	DRM_FORMAT_YUYV,
>  	DRM_FORMAT_YVYU,
>  	DRM_FORMAT_UYVY,
>  	DRM_FORMAT_VYUY,
> +	*/
>  	DRM_FORMAT_YUV411,
>  	DRM_FORMAT_YUV420,
>  	DRM_FORMAT_YUV422,
> -- 
> 2.27.0