Re: [RFC v2 PATCH v3 10/14] drm/panel: add S6E3FA0 driver

[YoungJun Cho <yj44.cho@samsung.com>]

On 04/29/2014 03:02 PM, YoungJun Cho wrote:
> Hi Laurent,
>
> Thank you for sharing your idea.
>
> On 04/29/2014 12:05 AM, Laurent Pinchart wrote:
>> Hi YoungJun,
>>
>> On Tuesday 22 April 2014 10:24:39 YoungJun Cho wrote:
>>> On 04/22/2014 08:00 AM, Laurent Pinchart wrote:
>>>> Hi YoungJun,
>>>>
>>>> Thank you for the patch.
>>>>
>>>> On Monday 21 April 2014 21:28:37 YoungJun Cho wrote:
>>>>> This patch adds MIPI-DSI command mode based S6E3FA0 AMOLED LCD Panel
>>>>> driver.
>>>>>
>>>>> Changelog v2:
>>>>> - Declares delay, size properties in probe routine instead of DT
>>>>> Changelog v3:
>>>>> - Moves CPU timings relevant properties from FIMD DT
>>>>>
>>>>>     (commented by Laurent Pinchart, Andrzej Hajda)
>>>>>
>>>>> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
>>>>> Acked-by: Inki Dae <inki.dae@samsung.com>
>>>>> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
>>>>> ---
>>>>>
>>>>>    drivers/gpu/drm/panel/Kconfig         |    7 +
>>>>>    drivers/gpu/drm/panel/Makefile        |    1 +
>>>>>    drivers/gpu/drm/panel/panel-s6e3fa0.c |  569
>>>>> ++++++++++++++++++++++++++
>>>>>    3 files changed, 577 insertions(+)
>>>>>    create mode 100644 drivers/gpu/drm/panel/panel-s6e3fa0.c
>>>>
>>>> [snip]
>>>>
>>>>> diff --git a/drivers/gpu/drm/panel/panel-s6e3fa0.c
>>>>> b/drivers/gpu/drm/panel/panel-s6e3fa0.c new file mode 100644
>>>>> index 0000000..1282678
>>>>> --- /dev/null
>>>>> +++ b/drivers/gpu/drm/panel/panel-s6e3fa0.c
>>>>> @@ -0,0 +1,569 @@
>>>>
>>>> [snip]
>>>>
>>>>> +static int s6e3fa0_get_modes(struct drm_panel *panel)
>>>>> +{
>>>>> +    struct drm_connector *connector = panel->connector;
>>>>> +    struct s6e3fa0 *ctx = panel_to_s6e3fa0(panel);
>>>>> +    struct drm_display_mode *mode;
>>>>> +
>>>>> +    mode = drm_mode_create(connector->dev);
>>>>> +    if (!mode) {
>>>>> +        DRM_ERROR("failed to create a new display mode\n");
>>>>> +        return 0;
>>>>> +    }
>>>>> +
>>>>> +    drm_display_mode_from_videomode(&ctx->vm, mode);
>>>>> +    mode->width_mm = ctx->width_mm;
>>>>> +    mode->height_mm = ctx->height_mm;
>>>>> +    connector->display_info.width_mm = mode->width_mm;
>>>>> +    connector->display_info.height_mm = mode->height_mm;
>>>>> +
>>>>> +    mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
>>>>> +    mode->private = (void *)&ctx->cpu_timings;
>>>>
>>>> Wouldn't it make sense to create a new get_interface_params (or
>>>> similar)
>>>> operation for drm_panel to query interface configuration parameters
>>>> instead of shoving it in the mode private field ?
>>>
>>> You mean "new get_interface_params operation" is different from
>>> get_modes() ?
>>>
>>> Till now, struct drm_display_mode and most of mode relevant APIs are
>>> only for video interface.
>>> And CPU interface also needs video mode configurations.
>>>
>>> I have a plan to implement the CPU interface relevant APIs like video
>>> mode ones, but I think they should be used under current DRM mode APIs
>>> like fill_modes, get_modes and so on.
>>> So after that implementation, this private field will be replaced by
>>> new ones.
>>>
>>> Could you explain it in more detail?
>>
>> The idea is that the interface parameters (RD/WR signals timings in
>> this case,
>> but this could also include MIPI DSI lane configuration or any other
>> kind of
>> physical interface parameters) are distinct from the video modes.
>
> Yes. The RD/WR signals timings are distinct from the video modes,
> but in my opinion, others are covered by video mode already.
>
>>
>> Do you see a need to tie tie interface parameters with
>> drm_display_mode ? Can
>> they be mode-specific ? In any case I'd like not to use the private
>> field of
>> drm_display_mode. If we need to tie both information together then it
>> should
>> be done in a standard way.
>
> I think this cpu-mode-timings is in struct drm_display_mode
> (NOT by *private) and requires drm_display_mode_from_cpumode()
> because the drm_display_mode_from_videomode() covers only video mode.
>
> I'll try implement it as soon as possible.
>

For your information, there are two modes in MIPI DSI specification,
which are video mode and command mode.
And CS, RD/WR timings are related with MIPI DBI specification,
VSYNC, HSYNC timings are related with MIPI DPI specification.

So I think all things relevant with command mode should be arranged
the name of command mode(NOT CPU mode, like video mode NOT RGB mode)
in MIPI DSI, and we don't need to consider MIPI DBI like we do MIPI DPI 
for video mode.

Thank you.
Best regards YJ

> Thank you,
> Best regards YJ.
>>
>
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