linux-kernel - Re: [PATCH v2 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

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Message-ID: <ldhyfuczwtwydwnvno4xn6ppjtt7mtcj35fp52xrqaajtfbtpb@2pgkytczb5k5>
Date: Sun, 27 Jul 2025 20:07:37 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Henrik Grimler <henrik@...mler.se>
Cc: 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>,
        dri-devel@...ts.freedesktop.org, linux-samsung-soc@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, replicant@...osl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] drm/bridge: sii9234: use extcon cable detection
 logic to detect MHL

On Thu, Jul 24, 2025 at 08:50:53PM +0200, Henrik Grimler wrote:
> To use MHL we currently need the MHL chip to be permanently on, which
> consumes unnecessary power. Let's use extcon attached to MUIC to enable
> the MHL chip only if it detects an MHL cable.

Does HPD GPIO reflect the correct state of the cable? What is the order
of events in such a case? Should the sii9234 signal to Exynos HDMI that
the link is established?

> 
> Signed-off-by: Henrik Grimler <henrik@...mler.se>
> ---
> v2: add dependency on extcon. Issue reported by kernel test robot
>     <lkp@...el.com>
> ---
>  drivers/gpu/drm/bridge/Kconfig   |  1 +
>  drivers/gpu/drm/bridge/sii9234.c | 89 ++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 87 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b9e0ca85226a603a24f90c6879d1499f824060cb..f18a083f6e1c6fe40bde5e65a1548acc61a162ae 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -303,6 +303,7 @@ config DRM_SII902X
>  config DRM_SII9234
>  	tristate "Silicon Image SII9234 HDMI/MHL bridge"
>  	depends on OF
> +	select EXTCON

Either this or 'depends on EXTCON || !EXTCON'

>  	help
>  	  Say Y here if you want support for the MHL interface.
>  	  It is an I2C driver, that detects connection of MHL bridge

-- 
With best wishes
Dmitry