Re: [PATCH 2/2] OMAPDSS: DISPC: Handle synclost errors in OMAP3

Mahapatra, Chandrabhanu
2012-03-16T14:15:42Z

2012/3/16 Tomi Valkeinen <tomi.valkeinen@ti.com>:
> On Fri, 2012-03-16 at 01:04 +0200, Ville Syrjälä wrote:
>> On Thu, Mar 15, 2012 at 05:18:52PM +0530, Chandrabhanu Mahapatra wrote:
>> > In OMAP3 DISPC video overlays suffer from some undocumented horizontal position
>> > and timing related limitations leading to SYNCLOST errors. Whenever the image
>> > window is moved towards the right of the screen SYNCLOST errors become
>> > frequent. Checks have been implemented to see that DISPC driver rejects
>> > configuration exceeding above limitations.
>> >
>> > This code was successfully tested on OMAP3. This code is written based on code
>> > written by Ville Syrjälä <ville.syrjala@nokia.com> in Linux OMAP kernel. Ville
>> > Syrjälä <ville.syrjala@nokia.com> had added checks for video overlay horizontal
>> > timing and DISPC horizontal blanking length limitations.
>> >
>> > Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com>
>> > ---
>> >  drivers/video/omap2/dss/dispc.c |   67 +++++++++++++++++++++++++++++++++++++--
>> >  1 files changed, 64 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
>> > index 5a1963e..ebfa613 100644
>> > --- a/drivers/video/omap2/dss/dispc.c
>> > +++ b/drivers/video/omap2/dss/dispc.c
>> > @@ -1622,6 +1622,58 @@ static void calc_dma_rotation_offset(u8 rotation, bool mirror,
>> >     }
>> >  }
>> >
>> > +static int check_horiz_timing(enum omap_channel channel, u16 pos_x,
>> > +           u16 width, u16 height, u16 out_width, u16 out_height)
>> > +{
>> > +   int DS = DIV_ROUND_UP(height, out_height);
>> > +   struct omap_dss_device *dssdev = dispc_mgr_get_device(channel);
>> > +   struct omap_video_timings t = dssdev->panel.timings;
>> > +   int pcd = REG_GET(DISPC_DIVISORo(channel), 7, 0);
>>
>> pcd doesn't exist for TV out, which is the reason why you see
>> 'lclk/pclk' ratio used instead in the harmattan kernel.
>
> I'm surprised you still remember these things =). And even more
> surprised that you actually bothered to review it, thanks for that.
>
> Chandrabhanu, do you have an omap3 board with composite/svideo tv-out?
> It'd be good to test on that also, as, like Ville points out, the above
> code can't work for tv-out. Hmm, then again, it shouldn't work for HDMI
> on OMAP4 either. Did you test with HDMI?
>
> Or is the above code called for TV-manager at all? If not, perhaps it
> could be named *_lcd or something. Or perhaps have a BUG_ON(channel !=
> lcd1 or lcd2);
>

Yes, I do have a Beagle board and I have tested on HDMI which works
without synclost errors upto 640 * 480 resolution.
The above errata exists only upto OMAP4430 ES1 which is currently not
supported. Please refer to errata 2.14 Downscaling Limitations in
errata sheet.
This patch is only for Omap3.

>  Tomi
>
>

--
Chandrabhanu Mahapatra
Texas Instruments India Pvt. Ltd.