linux-kernel - Re: [PATCH v4 03/11] drm/bridge: cdns-dsi: Fix Phy _init() and

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Date: Wed, 26 Jun 2024 13:25:15 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Aradhya Bhatia <a-bhatia1@...com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 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>, Jyri Sarha <jyri.sarha@....fi>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>
Cc: DRI Development List <dri-devel@...ts.freedesktop.org>,
 Linux Kernel List <linux-kernel@...r.kernel.org>,
 Dominik Haller <d.haller@...tec.de>, Sam Ravnborg <sam@...nborg.org>,
 Thierry Reding <treding@...dia.com>,
 Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
 Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Praneeth Bajjuri <praneeth@...com>, Udit Kumar <u-kumar1@...com>,
 Devarsh Thakkar <devarsht@...com>, Jayesh Choudhary <j-choudhary@...com>,
 Jai Luthra <j-luthra@...com>
Subject: Re: [PATCH v4 03/11] drm/bridge: cdns-dsi: Fix Phy _init() and
 _exit()

Hi,

On 22/06/2024 14:09, Aradhya Bhatia wrote:
> Initialize the Phy during the cdns-dsi _resume(), and de-initialize it
> during the _suspend().
> 
> Also power-off the Phy from bridge_disable.
> 
> Fixes: fced5a364dee ("drm/bridge: cdns: Convert to phy framework")
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>   drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> index 5159c3f0853e..d89c32bae2b9 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> @@ -672,6 +672,10 @@ static void cdns_dsi_bridge_disable(struct drm_bridge *bridge)
>   	if (dsi->platform_ops && dsi->platform_ops->disable)
>   		dsi->platform_ops->disable(dsi);
>   
> +	phy_power_off(dsi->dphy);
> +	dsi->link_initialized = false;
> +	dsi->phy_initialized = false;
> +
>   	pm_runtime_put(dsi->base.dev);
>   }
>   
> @@ -698,7 +702,6 @@ static void cdns_dsi_hs_init(struct cdns_dsi *dsi)
>   	       DPHY_CMN_PDN | DPHY_PLL_PDN,
>   	       dsi->regs + MCTL_DPHY_CFG0);
>   
> -	phy_init(dsi->dphy);
>   	phy_set_mode(dsi->dphy, PHY_MODE_MIPI_DPHY);
>   	phy_configure(dsi->dphy, &output->phy_opts);
>   	phy_power_on(dsi->dphy);
> @@ -1120,6 +1123,8 @@ static int __maybe_unused cdns_dsi_resume(struct device *dev)
>   	clk_prepare_enable(dsi->dsi_p_clk);
>   	clk_prepare_enable(dsi->dsi_sys_clk);
>   
> +	phy_init(dsi->dphy);
> +
>   	return 0;
>   }
>   
> @@ -1127,10 +1132,11 @@ static int __maybe_unused cdns_dsi_suspend(struct device *dev)
>   {
>   	struct cdns_dsi *dsi = dev_get_drvdata(dev);
>   
> +	phy_exit(dsi->dphy);
> +
>   	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;
>   }
>   

So with this patch, phy_init/exit will be called in the resume/suspend 
functions. That looks fine.

But the phy_power_on/phy_power_off looks odd to me. Here you add 
phy_power_off() to cdns_dsi_bridge_disable(), which sounds fine. But 
phy_power_on() is called in cdns_dsi_hs_init(), and that is called in 
cdns_dsi_bridge_enable() (which sounds fine), but also in 
cdns_dsi_bridge_pre_enable().

So doesn't that mean cdns_dsi_hs_init() call in cdns_dsi_bridge_enable() 
is extra, as it effectively does nothing (it exists right away if 
dsi->phy_initialized == true)?

  Tomi