[PATCH 2/2] [RFC] video: display: Adding frame related ops to MIPI DSI video source struct

[Vikas Sajjan]

Hi Laurent,

On 10 January 2013 05:05, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> Hi Vikas,
>
> Thank you for the patch.
>
> On Friday 04 January 2013 10:24:04 Vikas Sajjan wrote:
>> On 3 January 2013 16:29, Tomasz Figa <t.figa at samsung.com> wrote:
>> > On Wednesday 02 of January 2013 18:47:22 Vikas C Sajjan wrote:
>> >> From: Vikas Sajjan <vikas.sajjan at linaro.org>
>> >>
>> >> Signed-off-by: Vikas Sajjan <vikas.sajjan at linaro.org>
>> >> ---
>> >>
>> >>  include/video/display.h |    6 ++++++
>> >>  1 file changed, 6 insertions(+)
>> >>
>> >> diff --git a/include/video/display.h b/include/video/display.h
>> >> index b639fd0..fb2f437 100644
>> >> --- a/include/video/display.h
>> >> +++ b/include/video/display.h
>> >> @@ -117,6 +117,12 @@ struct dsi_video_source_ops {
>> >>
>> >>       void (*enable_hs)(struct video_source *src, bool enable);
>> >>
>> >> +     /* frame related */
>> >> +     int (*get_frame_done)(struct video_source *src);
>> >> +     int (*clear_frame_done)(struct video_source *src);
>> >> +     int (*set_early_blank_mode)(struct video_source *src, int power);
>> >> +     int (*set_blank_mode)(struct video_source *src, int power);
>> >> +
>> >
>> > I'm not sure if all those extra ops are needed in any way.
>> >
>> > Looking and Exynos MIPI DSIM driver, set_blank_mode is handling only
>> > FB_BLANK_UNBLANK status, which basically equals to the already existing
>> > enable operation, while set_early_blank mode handles only
>> > FB_BLANK_POWERDOWN, being equal to disable callback.
>>
>> Right, exynos_mipi_dsi_blank_mode() only supports FB_BLANK_UNBLANK as
>> of now, but FB_BLANK_NORMAL will be supported in future.
>> If not for Exynos, i think it will be need for other SoCs which
>> support FB_BLANK_UNBLANK and FB_BLANK_NORMAL.
>
> Could you please explain in a bit more details what the set_early_blank_mode
> and set_blank_mode operations do ?
>

with reference to Mr. Inki Dae's patch and discussion
http://lkml.indiana.edu/hypermail/linux/kernel/1109.1/00413.html
http://lkml.indiana.edu/hypermail/linux/kernel/1109.1/02247.html

set_early_blank_mode:
  - sets the framebuffer blank mode.
  - this callback should be called prior to fb_blank() by a client
driver only if needed
set_blank_mode:
  - sets framebuffer blank mode
  -  this callback should be called after fb_blank() by a client
driver only if needed.

In case of MIPI-DSI based video mode LCD Panel, for lcd power off, the
power off commands should be transferred to lcd panel with display and
mipi-dsi controller enabled, because the commands is set to lcd panel
at vsync porch period, hence set_early_blank_mode() was introduced and
should be called prior to fb_blank() as mentioned in the above 2
links.

I think Mr. Inki Dae can throw more light on this.

>> > Both get_frame_done and clear_frame_done do not look at anything used at
>> > the moment and if frame done status monitoring will be ever needed, I
>> > think a better way should be implemented.
>>
>> You are right, as of now Exynos MIPI DSI Panels are NOT using these
>> callbacks, but as you mentioned we will need frame done status monitoring
>> anyways, so i included these callbacks here. Will check, if we can implement
>> any better method.
>
> Do you expect the entity drivers (and in particular the panel drivers) to
> require frame done notification ? If so, could you explain your use case(s) ?
>
In our Exynos MIPI DSIM H/W, once MIPI DSIM transfers whole image
frame, interrupt will raised to indicate the same.
as part of the mipi_dsim_master_ops() we have get_dsim_frame_done()
and clear_dsim_frame_done() ops. But as of now we are also _NOT_ using
these ops in any particular use case. So i guess as of now we can park
it, later if we find any need for the same we can add it.

> --
> Regards,
>
> Laurent Pinchart
>

--
Thanks and Regards
 Vikas Sajjan
 SAMSUNG Research India - Banglore.