linux-kernel - Re: [PATCH] drm: bridge: dw-hdmi: Fix overflow workaround for Rockchip SoCs

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Message-ID: <20190222122814.GW3522@pendragon.ideasonboard.com>
Date:   Fri, 22 Feb 2019 14:28:14 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jonas Karlman <jonas@...boo.se>
Cc:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sean Paul <seanpaul@...omium.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Heiko Stuebner <heiko@...ech.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: bridge: dw-hdmi: Fix overflow workaround for
 Rockchip SoCs

Hi Jonas,

Thank you for the patch.

On Wed, Feb 20, 2019 at 07:52:31AM +0000, Jonas Karlman wrote:
> The Rockchip RK3288 SoC (v2.00a) and RK3328/RK3399 SoCs (v2.11a) have
> also been identified as needing this workaround with a single iteration.
> 
> Fixes: be41fc55f1aa ("drm: bridge: dw-hdmi: Handle overflow workaround based on device version")
> Signed-off-by: Jonas Karlman <jonas@...boo.se>

This makes me wonder if we have any device at all that doesn't need the
workaround... The HDMI encoder in R-Car SoCs doesn't seem to require it,
but it reports the same version number as on other SoCs that require the
workaround, and enabling it doesn't seem to affect R-Car adversely.
Should we thus enable it unconditionally ? Input from Synopsys would be
useful.

> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 64c3cf027518..14223c0ee784 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -1655,6 +1655,8 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
>  	 * iteration for others.
>  	 * The Amlogic Meson GX SoCs (v2.01a) have been identified as needing
>  	 * the workaround with a single iteration.
> +	 * The Rockchip RK3288 SoC (v2.00a) and RK3328/RK3399 SoCs (v2.11a) have
> +	 * been identified as needing the workaround with a single iteration.
>  	 */
>  
>  	switch (hdmi->version) {
> @@ -1663,7 +1665,9 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
>  		break;
>  	case 0x131a:
>  	case 0x132a:
> +	case 0x200a:
>  	case 0x201a:
> +	case 0x211a:
>  	case 0x212a:
>  		count = 1;
>  		break;

-- 
Regards,

Laurent Pinchart