On Tuesday 14 August 2012 11:03 PM, Tomi Valkeinen wrote:
On Tue, 2012-08-14 at 22:26 +0530, Archit Taneja wrote:
On Tuesday 14 August 2012 07:14 PM, Tomi Valkeinen wrote:
I guess it depends on how drm/fb want to use it. I guess an output
should have a set_timings() kind of op if it can do it seamlessly. I
guess we can do that easily in DPI, for example, we could reduce the fps
from 60 to 30 without causing an artefacts(I think). For outputs which
Yes, that kind of thing is easy to do by just changing the pck divider,
which is in a shadow register. I mean, "easy" in theory, at least. Our
clock calculation doesn't work like that currently, though, so it could
end up changing DSS fck.
can't do it, we could remove the set_timings totally.
But we do need set_timings for other outputs also (like sdi). We just
can't change them just like that. Only outputs that do not need timings
are DSI command mode and rfbi.
However, it'll be kind of inconsistent for some outputs to set timings,
and for others to not, and if in the future drm/fb gets exposed to ops
too, we may have dirty checks to see if set_timings is populated or not.
The easiest way would be to make all set_timings just update the copy of
the timings output has, and expect drm/fb to disable and re enable the
panel. We may end up doing unnecessary gpio resets and configuration of
the panels though.
I think changing things like timings is quite a rare operation. The only
case it'd be necessary to change timings often, with speed, and without
artifacts would be the fps drop you mentioned, for lower power use with
panels that don't mind the fps drop.
If I understood correctly, Rob said that drm already disables the output
when changing the mode, when I asked if it's ok for the apply's
set_timings to require the output to be off.
In any case this is not a big issue, I mean, it's not causing any
problems. Somebody is going to disable the output anyway when changing
the timings. Perhaps even these patches are good, because they make the
set_timings consistent across the output drivers (don't they?).
Yes, they do, there isn't a set_timings for RFBI though, only a
set_size, and DSI has set_timings for video mode and a set_size for
command mode, I haven't put checks in the ops for a panel driver to
wrongly call set_timings in commmand mode, and set_size in video mode.
I haven't done that yet because a future patch of mine will have a DSI
specific op called set_operation_mode() to make us independent of
dssdev->panel.dsi_mode, there is no guarantee that the panel driver to
first call set_operation_mode(), and then set_timings(), so I'm not sure
yet how to deal with that. Probably having a mode/state which says that
a field is unintialized might help, but that would overcomplicate things.
Archit
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