[PATCH V2 7/9] drm/bridge: ptn3460: add drm_panel controls

[Ajay kumar]

On Thu, Apr 24, 2014 at 10:55 PM, Rob Clark <robdclark at gmail.com> wrote:
> On Thu, Apr 24, 2014 at 12:55 PM, Ajay kumar <ajaynumb at gmail.com> wrote:
>> Rob,
>>
>> On Thu, Apr 24, 2014 at 9:41 PM, Rob Clark <robdclark at gmail.com> wrote:
>>> On Wed, Apr 23, 2014 at 3:02 PM, Ajay kumar <ajaynumb at gmail.com> wrote:
>>>> Sorry for the previous reply,
>>>>
>>>> Here goes the full explaination:
>>>>
>>>>> Rob,
>>>>>
>>>>> On Tue, Apr 22, 2014 at 5:04 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>>>> So what about, rather than adding drm_panel support to each bridge
>>>>>> individually, we introduce a drm_panel_bridge (with a form of
>>>>>> chaining).. ie:
>>>>>>
>>>>>>   struct drm_panel_bridge {
>>>>>>     struct drm_bridge base;
>>>>>>     struct drm_panel *panel;
>>>>>>     struct drm_bridge *bridge; /* optional */
>>>>>>   };
>>>>>>
>>>>>>   static void drm_panel_bridge_enable(struct drm_bridge *bridge)
>>>>>>   {
>>>>>>     struct drm_panel_bridge *pb = to_panel_bridge(bridge);
>>>>>>     if (pb->bridge)
>>>>>>       pb->bridge->funcs->enable(pb->bridge);
>>>>>>     pb->panel->funcs->enable(pb->panel);
>>>>>>   }
>>>>>>
>>>> We cannot call them like this from crtc helpers in the order you mentioned,
>>>> since each individual bridge chip expects the panel controls at
>>>> different places.
>>>> I mean,
>>>> -- sometimes panel controls needs to be done before bridge
>>>> controls(ptn3460: before RST_N and PD_N)
>>>
>>> well, this is why bridge has pre-enable/enable/disable/post-disable
>>> hooks, so you can choose before or after..
>> These calls are for a bridge to sync with the encoder calls.
>> We might end up defining pre-enable/enable/disable/post-disable for a
>> panel to sync
>> with the bridge calls! I have explained below.
>>
>>>> -- sometimes in between the bridge controls (ps8622: one panel control
>>>> before SLP_N and one after SLP_N)
>>>> -- sometimes panel controls needs to be done after bridge controls.
>>>
>>> I am not convinced that a generic panel/bridge adapter is not
>>> possible.  Maybe we need more fine grained fxn ptr callbacks, although
>>> seems like pre+post should give you enough.  It would certainly be
>>> easier than having to add panel support in each individual bridge
>>> driver (which seems like it will certainly result that only certain
>>> combinations of panel+bridge actually work as intended)
>> Ok. Consider this case:
>> Currently, we have the sequence as "bridge->pre_enable,
>> encoder_enable, bridge->enable"
>> And, the bridge should obviously be enabled in bridge->pre_enable.
>> Now, where do you choose to call panel->pre_enable?
>> -- as the first step of bridge->pre_enable, before we pull up/down bridge GPIOs.
>> -- at the last step of bridge->pre_enable, after we pull up/down the
>> bridge GPIOs.
>>
>> Ideally, PTN3460 expects it to be the second case, and PS8625 expects
>> it to be the first case.
>> So, we will end up adding pre_pre_enable, post_pre_enable to
>> accomodate such scenarios.
>
> ok, well I think we can deal with this with a slight modification of
> my original proposal.  Split drm_panel_bridge into
> drm_composite_bridge and drm_panel_bridge:
>
>   struct drm_composite_bridge {
>     struct drm_bridge base;
>     struct drm_bridge *b1, *b2;
>   }
>
>   static void drm_composite_bridge_enable(struct drm_bridge *bridge)
>   {
>     struct drm_composite_bridge *cbridge = to_composite_bridge(bridge);
>     cbridge->b1->funcs->enable(cbridge->b1);
>     cbridge->b2->funcs->enable(cbridge->b2);
>   }
>
>   .. and so on ..
>
>   struct drm_panel_bridge {
>     struct drm_bridge base;
>     struct drm_panel *panel;
>   }
>
>   static void drm_panel_bridge_enable(struct drm_bridge *bridge)
>   {
>     struct drm_panel_bridge *pbridge = to_panel_bridge(bridge);
>     pbridge->panel->funcs->enable(pbridge->panel);
>   }
>
>   .. and so on..
>
>
> then in initialization, order can be managed like:
>
>   if (panel_first)
>     bridge = drm_composite_bridge_init(panel_bridge, actual_bridge)
>   else
>     bridge = drm_composite_bridge_init(actual_bridge, panel_bridge);
>
>   possibly parametrize drm_panel_bridge if we need to map
> panel->enable() to bridge->pre_enable() vs bridge->enable(), etc..

Well, this really does seems complex to me.
Don't you think just having a drm_panel inside drm_bridge structure is
sufficient?!
And, make a call for pre_panel_enable and post_panel_enable around
bridge->pre_enable..and so on.?