[PATCHv3 28/30] drm/omap: fix display SYNC/DE flags

[Tomi Valkeinen]

On 29/03/17 11:58, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Tuesday 28 Mar 2017 16:08:14 Tomi Valkeinen wrote:
>> At the moment VSYNC/HSYNC/DE high/low flags set by the panel/encoder
>> drivers get lost when the videotimings are translated to DRM's
>> videomode, as DRM's mode does not have corresponding flags.
>>
>> DRM has bus-flags for this purpose, and while it lacks a few flags at
>> the moment, it should be used here. However, until we rewrite omapdrm's
>> device model, using bus-flags is rather difficult.
>>
>> As a short term fix, this patch makes sure that every time the videomode
>> is set in omap_crtc_mode_set_nofb(), the driver asks for the SYNC/DE
>> flags from the panel/encoder drivers, and thus we get the correct flags
>> into use.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
>> ---
>>  drivers/gpu/drm/omapdrm/omap_connector.c |  2 --
>>  drivers/gpu/drm/omapdrm/omap_crtc.c      | 28 +++++++++++++++++++++++++---
>>  2 files changed, 25 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/omapdrm/omap_connector.c
>> b/drivers/gpu/drm/omapdrm/omap_connector.c index 50d2b641c28b..d62c035f050f
>> 100644
>> --- a/drivers/gpu/drm/omapdrm/omap_connector.c
>> +++ b/drivers/gpu/drm/omapdrm/omap_connector.c
>> @@ -146,8 +146,6 @@ static int omap_connector_mode_valid(struct
>> drm_connector *connector, int r, ret = MODE_BAD;
>>
>>  	drm_display_mode_to_videomode(mode, &vm);
>> -	vm.flags |= DISPLAY_FLAGS_DE_HIGH | DISPLAY_FLAGS_PIXDATA_POSEDGE |
>> -		    DISPLAY_FLAGS_SYNC_NEGEDGE;
> 
> The dssdrv->get_timings() call below will return a video mode with polarity 
> flags set, which will then be compared to vm. As you don't set the vm flags 
> anymore, won't the comparison fail ?

Hmm, true. We never go to that code path, though, as we have
check_timings in all the drivers, except panel-dsi-cs.c (but there's a
patch adding it). And the panels don't check the flags, only things like
resolution or porches.

I think we can just require all drivers to have check_timings. It's
hiding the problem a bit, but should work fine until this can be solved
properly.

Or actually, perhaps as a quick fix I should change the check to ignore
the flags for now.

>>  	mode->vrefresh = drm_mode_vrefresh(mode);
>>
>>  	/*
>> diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c
>> b/drivers/gpu/drm/omapdrm/omap_crtc.c index 1db96b077ae8..606ef807741a
>> 100644
>> --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
>> +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
>> @@ -373,6 +373,11 @@ static void omap_crtc_mode_set_nofb(struct drm_crtc
>> *crtc) {
>>  	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
>>  	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
>> +	struct omap_drm_private *priv = crtc->dev->dev_private;
>> +	const u32 flags_mask = DISPLAY_FLAGS_DE_HIGH | DISPLAY_FLAGS_DE_LOW |
>> +		DISPLAY_FLAGS_PIXDATA_POSEDGE | DISPLAY_FLAGS_PIXDATA_NEGEDGE 
> |
>> +		DISPLAY_FLAGS_SYNC_POSEDGE | DISPLAY_FLAGS_SYNC_NEGEDGE;
>> +	int i;
> 
> i only takes positive values, you can make it an unsigned int.

Yep.

>>
>>  	DBG("%s: set mode: %d:\"%s\" %d %d %d %d %d %d %d %d %d %d 0x%x 0x%x",
>>  	    omap_crtc->name, mode->base.id, mode->name,
>> @@ -382,9 +387,26 @@ static void omap_crtc_mode_set_nofb(struct drm_crtc
>> *crtc) mode->type, mode->flags);
>>
>>  	drm_display_mode_to_videomode(mode, &omap_crtc->vm);
>> -	omap_crtc->vm.flags |= DISPLAY_FLAGS_DE_HIGH |
>> -			       DISPLAY_FLAGS_PIXDATA_POSEDGE |
>> -			       DISPLAY_FLAGS_SYNC_NEGEDGE;
>> +
> 
> Could you add a HACK/FIXME comment to explain how this should be fixed 
> properly ? I want to make sure we won't forget to remove this hack.

I'll add a comment. I don't know exactly how this should be fixed, but
at least I can explain the hack there.

 Tomi

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