linux-kernel - Re: [PATCH v2] drm/bridge: adv7533: Reset DSI receiver logic

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Message-ID: <26b95b57-05b6-40c8-b64c-2cb1ae5e8454@kontron.de>
Date: Tue, 10 Dec 2024 16:21:09 +0100
From: Frieder Schrempf <frieder.schrempf@...tron.de>
To: Stefan Ekenberg <stefan.ekenberg@...s.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 kernel@...s.com, Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2] drm/bridge: adv7533: Reset DSI receiver logic

On 19.11.24 8:42 AM, Stefan Ekenberg wrote:
> Reset DSI receiver logic during power on. The need for this change was
> discovered when investigating issue with ADV7535. The symptom of the
> problem was that ADV7535 continuously outputs a black image. This
> happened for about 10% of the times that ADV7535 was powered on. The
> rest of the times the image was as expected.
> 
> The solution in this patch (placement of reset and sleep time of 200ms)
> is implemented as outlined by the Analog Devices support team.
> 
> Tested-by: Biju Das <biju.das.jz@...renesas.com>
> Signed-off-by: Stefan Ekenberg <stefan.ekenberg@...s.com>

If this is a generic issue for this chip, it would be great if we could
add a Fixes tag here to get this backported. Depending on the scope
(ADV7533 + ADV7535 or only ADV7535), candidates would be:

  * 2437e7cd88e87 ("drm/bridge: adv7533: Initial support for ADV7533")
  * 8501fe4b14a35 ("drm: bridge: adv7511: Add support for ADV7535")

Thanks!

> ---
> Changes in v2:
> - Add Tested-by tag
> - Link to v1: https://lore.kernel.org/r/20241113-adv7533-dsi-reset-v1-1-6c1069e35fd3@axis.com
> ---
>  drivers/gpu/drm/bridge/adv7511/adv7533.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7533.c b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> index 4481489aaf5ebf164313c86cbf3447d2d7914ab9..93085c2b872ed98f4ee394236dc66c568c0e5ccf 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7533.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> @@ -67,6 +67,15 @@ void adv7533_dsi_power_on(struct adv7511 *adv)
>  {
>  	struct mipi_dsi_device *dsi = adv->dsi;
>  
> +	/*
> +	 * Reset DSI receiver block logic to avoid ADV7535 startup problem.
> +	 * Without this reset it sometimes continuously fails to receive
> +	 * incoming DSI packets and outputs black image.
> +	 */
> +	regmap_write(adv->regmap_cec, 0x26, 0x18);
> +	msleep(200);
> +	regmap_write(adv->regmap_cec, 0x26, 0x38);
> +
>  	if (adv->use_timing_gen)
>  		adv7511_dsi_config_timing_gen(adv);
>  
> 
> ---
> base-commit: 59b723cd2adbac2a34fc8e12c74ae26ae45bf230
> change-id: 20241108-adv7533-dsi-reset-488c6fbb5e42
> 
> Best regards,