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

[Marek Vasut]

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 ?