linux-kernel - Re: [PATCH v1 2/5] drm: bridge: dw_hdmi: enable overflow workaround for v2.13a

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Message-ID: <45668d73-a9fb-b23a-fb32-2e50eb4982aa@baylibre.com>
Date:   Wed, 6 Apr 2022 11:17:25 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Sandor.yu@....com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, andrzej.hajda@...el.com,
        robert.foss@...aro.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com
Cc:     shengjiu.wang@....com, cai.huoqing@...ux.dev, maxime@...no.tech,
        harry.wentland@....com, hverkuil-cisco@...all.nl,
        amuel@...lland.org
Subject: Re: [PATCH v1 2/5] drm: bridge: dw_hdmi: enable overflow workaround
 for v2.13a

Hi,

On 06/04/2022 10:48, Sandor.yu@....com wrote:
> From: Sandor Yu <Sandor.yu@....com>
> 
> iMX865 HDMI (v2.13a) have been identified as needing the workaround.
> Tests show that one iteration is enough.
> 
> Without the workaround, iMX865 HDMI audio may not work
> after cable plugout/in, because HDMI mode is not really set in
> register HDMI_FC_INVIDCONF.
> 
> Signed-off-by: Sandor Yu <Sandor.yu@....com>
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 4befc104d220..b11577de4836 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2087,9 +2087,9 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
>   	 *
>   	 * The number of iterations matters and depends on the HDMI TX revision
>   	 * (and possibly on the platform). So far i.MX6Q (v1.30a), i.MX6DL
> -	 * (v1.31a) and multiple Allwinner SoCs (v1.32a) have been identified
> -	 * as needing the workaround, with 4 iterations for v1.30a and 1
> -	 * iteration for others.
> +	 * (v1.31a), iMX865(v2.13a) and multiple Allwinner SoCs (v1.32a)
> +	 * have been identified as needing the workaround,
> +	 * with 4 iterations for v1.30a and 1 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
> @@ -2106,6 +2106,7 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
>   	case 0x201a:
>   	case 0x211a:
>   	case 0x212a:
> +	case 0x213a:
>   		count = 1;
>   		break;

At some point we must consider only v1.30a needs 4, and other needs 1.

It would be simpler to put the "count = 1" in a default case.

The comment change is still welcome so we can track.

Thanks,
Neil

>   	default: