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From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Jernej Skrabec <jernej.skrabec@siol.net>
Cc:     maxime.ripard@bootlin.com, wens@csie.org, robh+dt@kernel.org,
        sboyd@kernel.org, airlied@linux.ie, architt@codeaurora.org,
        a.hajda@samsung.com, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-clk@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-sunxi@googlegroups.com
Subject: Re: [PATCH v2 15/29] drm/bridge/synopsys: dw-hdmi: Enable workaround for v2.12a
Date:   Tue, 09 Oct 2018 20:40:44 +0300
Message-ID: <3616158.EzHeIcd69b@avalon>
Organization: Ideas on Board Oy
In-Reply-To: <20181007093905.11253-16-jernej.skrabec@siol.net>
References: <20181007093905.11253-1-jernej.skrabec@siol.net> <20181007093905.11253-16-jernej.skrabec@siol.net>
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Hi Jernej,

Thank you for the patch.

On Sunday, 7 October 2018 12:38:51 EEST Jernej Skrabec wrote:
> It turns out that even new DW HDMI controllers exhibits same magenta
> line issues as older versions.
> 
> Enable workaround for v2.12a.

This doesn't affect the platforms I maintain, so I can't really test this, but 
I'm wondering whether there could be other platforms using a v2.12a DW HDMI 
that wouldn't need the workaround.

My platforms use a previous version, namely v2.01a. The workaround for that 
version has been enabled by

commit 9c305eb442f3b371fc722ade827bbf673514123e
Author: Neil Armstrong <narmstrong@baylibre.com>
Date:   Fri Feb 23 12:44:37 2018 +0100

    drm: bridge: dw-hdmi: Fix overflow workaround for Amlogic Meson GX SoCs

I haven't paid too much attention to the patch back then, and have now double-
checked the HDMI output on R-Car Gen3. Enabling the workaround doesn't cause 
any regression, and reverting the commit doesn't cause any issue either. I 
thus wonder whether we shouldn't enable the workaround with count = 1 in the 
default case instead of adding new IP core versions to the list. It would be 
nice if someone from Synopsys could comment on this.

> Reviewed-by: Chen-Yu Tsai <wens@csie.org>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index
> 5971976284bf..df1c7a2d6961 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -1664,6 +1664,7 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi
> *hdmi) case 0x131a:
>  	case 0x132a:
>  	case 0x201a:
> +	case 0x212a:
>  		count = 1;
>  		break;
>  	default:

-- 
Regards,

Laurent Pinchart