linux-kernel - Re: [PATCH v2 15/29] drm/bridge/synopsys: dw-hdmi: Enable workaround for v2.12a

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Date:   Tue, 09 Oct 2018 20:40:44 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     maxime.ripard@...tlin.com, wens@...e.org, robh+dt@...nel.org,
        sboyd@...nel.org, airlied@...ux.ie, architt@...eaurora.org,
        a.hajda@...sung.com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v2 15/29] drm/bridge/synopsys: dw-hdmi: Enable workaround for v2.12a

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@...libre.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@...e.org>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.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