linux-kernel - Re: [PATCH v3 02/10] drm/bridge: cdns-dsi: Fix the phy

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Date: Wed, 19 Jun 2024 17:26:16 +0530
From: Aradhya Bhatia <a-bhatia1@...com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Tomi Valkeinen <tomi.valkeinen@...asonboard.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>, Jyri
 Sarha <jyri.sarha@....fi>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David
 Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        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 v3 02/10] drm/bridge: cdns-dsi: Fix the phy_initialized
 variable



On 18/06/24 01:04, Dmitry Baryshkov wrote:
> On Mon, 17 Jun 2024 at 17:16, Aradhya Bhatia <a-bhatia1@...com> wrote:
>>
>> Hi Dmitry,
>>
>> Thanks for reviewing the patches!
>>
>> On 17/06/24 17:29, Dmitry Baryshkov wrote:
>>> On Mon, Jun 17, 2024 at 04:23:03PM GMT, Aradhya Bhatia wrote:
>>>> Update the Phy initialized state to "not initialized" when the driver
>>>> (and the hardware by extension) gets suspended. This will allow the Phy
>>>> to get initialized again after resume.
>>>>
>>>> Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
>>>> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
>>>> ---
>>>>  drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>>>> index b016f2ba06bb..42565e253b2d 100644
>>>> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>>>> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>>>> @@ -1153,6 +1153,7 @@ static int __maybe_unused cdns_dsi_suspend(struct device *dev)
>>>>      clk_disable_unprepare(dsi->dsi_p_clk);
>>>>      reset_control_assert(dsi->dsi_p_rst);
>>>>      dsi->link_initialized = false;
>>>
>>> Most likely you should also call phy_exit() here. And in _remove() too.
>>
>> I agree that phy_exit should be called here. But why in _remove()?
>> Wouldn't having phy_exit in 2 places mess up the internal ref count?
> 
> If suspend() is going to be called in the teardown path, then it's
> fine to have just one call here. Otherwise you might add one guarded
> with if (phy_initialized) to _remove() too.

Since the _suspend() and _resume() hooks are registered for both, system
sleep PM and runtime PM, the _suspend() hook does get called when I
remove the cdns_dsi module using modprobe. Tested that on my setup.

I believe having phy_exit() only in  _suspend() would suffice for now.

> 
>>
>>>
>>>> +    dsi->phy_initialized = false;
>>>>      return 0;
>>>>  }
>>>>
>>>> --
>>>> 2.34.1
>>>>
>>>
>> --
>> Regards
>> Aradhya
> 
> 
> 

--
Regards
Aradhya