On Wednesday 23 November 2011 04:12 PM, Tomi Valkeinen wrote:
On Wed, 2011-11-23 at 15:40 +0530, Archit Taneja wrote:
On Tuesday 22 November 2011 02:51 PM, Tomi Valkeinen wrote:
The current code uses dsi_video_mode_enable/disable functions to
enable/disable DISPC output for video mode displays. For command mode
displays we have no notion in the DISPC side of whether the panel is
enabled, except when a dss_start_update() call is made.
However, to properly maintain the DISPC state in apply.c, we need to
know if a manager used for a manual update display is currently in use.
This patch achieves that by changing dsi_video_mode_enable/disable to
dsi_enable/disable_video_output, which is called by both video and
command mode displays. For video mode displays it starts the actual
pixel stream, as it did before. For command mode displays it doesn't do
anything else than mark that the manager is currently in use.
dsi_video_mode_enable() doesn't only enable the DISPC output, it also
sends the long packet header to start video mode transfer.
I think it would be better if we had 2 separate functions, one which
starts/stops DSI video mode, and the other which enables/disables the
DISPC video port.
This way, a manual update panel would need to call only
dsi_enable/disable_video_output(which just enables or disables the
manager), whereas a video mode panel will need to call both.
This is just a suggestion though. It's probably okay to have both in the
same function too. We might have to separate them out later if we were
planning to standardise mipi dsi across SoCs.
If you think from the panel driver's point of view, it doesn't know
about DISPC. It just wants to enable the video stream (on video mode
displays).
If we had two functions, could only the first be used? I.e. is it
possible to just enable the video mode transfer, without enabling DISPC?
If not, I'm not sure what would be the use for two separate functions.
And even if it can, I'm not sure what use it would be to enable only the
video mode output without the actual pixel data from DISPC.
It is true that the function in thsi patch is not the best one. For
command mode display it's more about reserving the ovl manager for use
than actually enabling it. Then again, how I thought the function's
purpose was that it enables the DSI video output, but because for
command mode there's need to trigger the actual frame transfer later,
the function doesn't start the pixel feed for command mode displays. It
just "prepares" the output.
But even if we had the functions separated, the function called by video
mode and command mode displays would be different, as for the former one
it enables the pixel stream, and for latter one it just reserves the
output.
So, I'm fine with changing the function, but the reasoning for what
functions we have and what they do should come from the panel driver's
perspective, not because of OMAP DSS's HW details.
If you look from the panel driver's perspective, we shouldn't split this.
I think it would be best to stuff the 'video mode enabling and manager
enabling' functionality in omapdss_dsi_display_enable() itself, the
panel driver shouldn't need to call a function separately to enable
video mode for the panel. This way we would be more along the lines of
the dpi driver, where dpi_display_enable() enables the manager in the end.
I guess we can leave this the way you are doing it currently, and move
this code into dsi_display_enable() code later on.
Archit
Tomi
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