[PATCH] drm: bridge: dw-mipi-dsi: Drop panel_bridge post_disable call

[Marek Vasut]

On 5/16/23 10:25, Jagan Teki wrote:
> On Tue, May 16, 2023 at 1:47 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 5/16/23 10:12, Jagan Teki wrote:
>>> Hi Marek and Neil,
>>>
>>> On Sun, May 14, 2023 at 1:40 AM Marek Vasut <marex at denx.de> wrote:
>>>>
>>>> This panel_bridge post_disable callback is called from the bridge chain now,
>>>> so drop the explicit call here. This fixes call imbalance, where this driver
>>>> does not call ->pre_enable, but does call ->post_disable . In case either of
>>>> the two callbacks implemented in one of the panel or bridge drivers contains
>>>> any operation with refcounted object, like regulator, this would make kernel
>>>> complain about the imbalance.
>>>>
>>>> This can be triggered e.g. with ST7701 driver, which operates on regulators
>>>> in its prepare/unprepare callbacks, which are called from pre_enable/post_disable
>>>> callbacks respectively. The former is called once, the later twice, during
>>>> entry to suspend.
>>>>
>>>> Drop the post_disable call to fix the imbalance.
>>>>
>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>> ---
>>>> Cc: Andrzej Hajda <andrzej.hajda at intel.com>
>>>> Cc: Antonio Borneo <antonio.borneo at foss.st.com>
>>>> Cc: Daniel Vetter <daniel at ffwll.ch>
>>>> Cc: David Airlie <airlied at gmail.com>
>>>> Cc: Jernej Skrabec <jernej.skrabec at gmail.com>
>>>> Cc: Jonas Karlman <jonas at kwiboo.se>
>>>> Cc: Laurent Pinchart <Laurent.pinchart at ideasonboard.com>
>>>> Cc: Marek Vasut <marex at denx.de>
>>>> Cc: Neil Armstrong <neil.armstrong at linaro.org>
>>>> Cc: Philipp Zabel <p.zabel at pengutronix.de>
>>>> Cc: Philippe Cornu <philippe.cornu at foss.st.com>
>>>> Cc: Robert Foss <robert.foss at linaro.org>
>>>> Cc: Vincent Abriou <vincent.abriou at st.com>
>>>> Cc: Yannick Fertre <yannick.fertre at foss.st.com>
>>>> Cc: dri-devel at lists.freedesktop.org
>>>> ---
>>>>    drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 9 ---------
>>>>    1 file changed, 9 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>>>> index b2efecf7d1603..63ac972547361 100644
>>>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>>>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>>>> @@ -859,15 +859,6 @@ static void dw_mipi_dsi_bridge_post_atomic_disable(struct drm_bridge *bridge,
>>>>            */
>>>>           dw_mipi_dsi_set_mode(dsi, 0);
>>>>
>>>> -       /*
>>>> -        * TODO Only way found to call panel-bridge post_disable &
>>>> -        * panel unprepare before the dsi "final" disable...
>>>> -        * This needs to be fixed in the drm_bridge framework and the API
>>>> -        * needs to be updated to manage our own call chains...
>>>> -        */
>>>> -       if (dsi->panel_bridge->funcs->post_disable)
>>>> -               dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>>>> -
>>>
>>> If my understanding was correct, the controller set the low-speed DCS
>>> in pre_enable and high-speed DCS in enable. So I'm thinking this
>>> explicit post_disable still needs to revert the operation within the
>>> bridge chain. I didn't test this but trying to understand how the
>>> existing behaviour is satisfied if we drop this.
>>
>> Did I miss a panel_bridge pre_enable call somewhere in the driver ?
>> Where is it ?
> 
> Haa, sorry the next bridge pre_enable.  driver setting the
> command-mode (low-speed) in mode_set so when the next bridge
> pre_enable is called, low-speed DCS can be sent, then the bridge
> enable() sets video mode (high-speed). This is where an explicit
> post_disable would be required, this is what I understood so far.

So, in the end, all is good with this patch or is there anything missing ?