linux-kernel - Re: [PATCH v7 03/12] drm/bridge: cdns-dsi: Fix phy de-init and flag it so

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Message-ID: <84ca02de-9788-4e16-bf24-1651bd365ebd@ideasonboard.com>
Date: Tue, 14 Jan 2025 14:30:17 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
Cc: Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Devarsh Thakkar <devarsht@...com>, Praneeth Bajjuri <praneeth@...com>,
 Udit Kumar <u-kumar1@...com>, Jayesh Choudhary <j-choudhary@...com>,
 DRI Development List <dri-devel@...ts.freedesktop.org>,
 Linux Kernel List <linux-kernel@...r.kernel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 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>
Subject: Re: [PATCH v7 03/12] drm/bridge: cdns-dsi: Fix phy de-init and flag
 it so

Hi,

On 14/01/2025 07:56, Aradhya Bhatia wrote:
> From: Aradhya Bhatia <a-bhatia1@...com>
> 
> The driver code doesn't have a Phy de-initialization path as yet, and so
> it does not clear the phy_initialized flag while suspending. This is a
> problem because after resume the driver looks at this flag to determine
> if a Phy re-initialization is required or not. It is in fact required
> because the hardware is resuming from a suspend, but the driver does not
> carry out any re-initialization causing the D-Phy to not work at all.
> 
> Call the counterparts of phy_init() and phy_power_on(), that are
> phy_exit() and phy_power_off(), from _bridge_disable(), and clear the
> flags so that the Phy can be initialized again when required.
> 
> Fixes: fced5a364dee ("drm/bridge: cdns: Convert to phy framework")
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> Signed-off-by: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
> ---
>   drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> index 056583e81155..039c5eb7fb66 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> @@ -672,6 +672,11 @@ static void cdns_dsi_bridge_disable(struct drm_bridge *bridge)
>   	if (dsi->platform_ops && dsi->platform_ops->disable)
>   		dsi->platform_ops->disable(dsi);
>   
> +	dsi->phy_initialized = false;
> +	dsi->link_initialized = false;
> +	phy_power_off(dsi->dphy);
> +	phy_exit(dsi->dphy);
> +

The phy related lines are counterparts to what's done in 
cdns_dsi_hs_init(), right? Maybe add cdns_dsi_hs_uninit(),

But is the phy_initialized even needed? phy_initialized() is called from 
cdns_dsi_bridge_enable() and cdns_dsi_bridge_pre_enable(). Won't the 
call in cdns_dsi_bridge_enable() be always skipped, as 
cdns_dsi_bridge_pre_enable() already set phy_initialized?

Same question for cdns_dsi_init_link(), although that's also called from 
cdns_dsi_transfer(), so we probably need dsi->link_initialized.

  Tomi

>   	pm_runtime_put(dsi->base.dev);
>   }
>   
> @@ -1130,7 +1135,6 @@ static int __maybe_unused cdns_dsi_suspend(struct device *dev)
>   	clk_disable_unprepare(dsi->dsi_sys_clk);
>   	clk_disable_unprepare(dsi->dsi_p_clk);
>   	reset_control_assert(dsi->dsi_p_rst);
> -	dsi->link_initialized = false;
>   	return 0;
>   }
>