[PATCH] drm/modes: do not enforce an odd vtotal for interlaced modes

[PATCH] drm/modes: do not enforce an odd vtotal for interlaced modes

[Daniel Vetter]

CEA actually specifies an interlaced mode with even vtotal and
supplies a diagram showing how this is supposed to work.

Note that interlaced modes with an even vtotal seem to be a fairly
recent invention. All modelines lore I could dig up with googling says
that vtotal for interlaced modes _needs_ to be odd. But the even
modelines in CEA are not a spec-bug, there's a figure in CEA-861-E
called "Figure 5 Special Interlaced Video Format Timing (Even Vtotal)"
that explains how it's supposed to work. Furthermore intel Bspec
explicitly mentions that both odd and even interlaced vtotal are
supported (VTOTAL register in the south display engine of PCH split
chips).

Cc: Adam Jackson <ajax@redhat.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_modes.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index fb8e46b..7ff13bc 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -686,8 +686,6 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
 			p->crtc_vsync_end /= 2;
 			p->crtc_vtotal /= 2;
 		}
-
-		p->crtc_vtotal |= 1;
 	}
 
 	if (p->flags & DRM_MODE_FLAG_DBLSCAN) {
-- 
1.7.7.5

Re: [PATCH] drm/modes: do not enforce an odd vtotal for interlaced modes

[Dave Airlie]

On Fri, Jan 27, 2012 at 9:40 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> CEA actually specifies an interlaced mode with even vtotal and
> supplies a diagram showing how this is supposed to work.
>
> Note that interlaced modes with an even vtotal seem to be a fairly
> recent invention. All modelines lore I could dig up with googling says
> that vtotal for interlaced modes _needs_ to be odd. But the even
> modelines in CEA are not a spec-bug, there's a figure in CEA-861-E
> called "Figure 5 Special Interlaced Video Format Timing (Even Vtotal)"
> that explains how it's supposed to work. Furthermore intel Bspec
> explicitly mentions that both odd and even interlaced vtotal are
> supported (VTOTAL register in the south display engine of PCH split
> chips).
>
> Cc: Adam Jackson <ajax@redhat.com>
> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---

Ajax? I'd like your ack/review on this.

Thanks,
Dave.

Re: [PATCH] drm/modes: do not enforce an odd vtotal for interlaced modes

[Adam Jackson]

On 2/3/12 4:37 AM, Dave Airlie wrote:
> On Fri, Jan 27, 2012 at 9:40 PM, Daniel Vetter<daniel.vetter@ffwll.ch>  wrote:
>> CEA actually specifies an interlaced mode with even vtotal and
>> supplies a diagram showing how this is supposed to work.
>>
>> Note that interlaced modes with an even vtotal seem to be a fairly
>> recent invention. All modelines lore I could dig up with googling says
>> that vtotal for interlaced modes _needs_ to be odd. But the even
>> modelines in CEA are not a spec-bug, there's a figure in CEA-861-E
>> called "Figure 5 Special Interlaced Video Format Timing (Even Vtotal)"
>> that explains how it's supposed to work. Furthermore intel Bspec
>> explicitly mentions that both odd and even interlaced vtotal are
>> supported (VTOTAL register in the south display engine of PCH split
>> chips).
>>
>> Cc: Adam Jackson<ajax@redhat.com>
>> Signed-Off-by: Daniel Vetter<daniel.vetter@ffwll.ch>
>> ---
>
> Ajax? I'd like your ack/review on this.

That |= 1 logic was just slavishy copied from the server's RANDR code, 
which afaict slavishly copied it from xfree86 4, and I think even that 
was copypasta from xfree86 3.  I don't know what it was ever meant to do.

- ajax