mx6 hdmi resolution behaviour

mx6 hdmi resolution behaviour

[Fabio Estevam]

Hi,

On a imx6q-cubox-i running 4.1 kernel I am getting 1920x1080 HDMI
resolution if I boot the board with the HDMI cable connected.

If I boot it without the HDMI cable and then connect it afterwards,
the resolution goes to only 1024 x 768 and the following IPU message
is seen:

[   16.310548] imx-ipuv3 2400000.ipu: videomode adapted for IPU restrictions

Shouldn't we get 1920x1080 in this case as well?

Regards,

Fabio Estevam

mx6 hdmi resolution behaviour

[Russell King - ARM Linux]

On Tue, Jun 23, 2015 at 01:41:46PM -0300, Fabio Estevam wrote:
> Hi,
> 
> On a imx6q-cubox-i running 4.1 kernel I am getting 1920x1080 HDMI
> resolution if I boot the board with the HDMI cable connected.
> 
> If I boot it without the HDMI cable and then connect it afterwards,
> the resolution goes to only 1024 x 768 and the following IPU message
> is seen:

If you have no connected connectors, then you get 1024x768:

imx-drm display-subsystem: No connectors reported connected with modes
[drm] Cannot find any crtc or sizes - going 1024x768

as that's what DRM defaults to when it has no other timing information
available.

> [   16.310548] imx-ipuv3 2400000.ipu: videomode adapted for IPU restrictions

I don't see this message booting on a Hummingboard with HDMI
disconnected.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

mx6 hdmi resolution behaviour

[Fabio Estevam]

On Tue, Jun 23, 2015 at 1:44 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:

> If you have no connected connectors, then you get 1024x768:
>
> imx-drm display-subsystem: No connectors reported connected with modes
> [drm] Cannot find any crtc or sizes - going 1024x768
>
> as that's what DRM defaults to when it has no other timing information
> available.

Agreed, but after the cable is connected we could try to find a more
suitable timing?

>> [   16.310548] imx-ipuv3 2400000.ipu: videomode adapted for IPU restrictions
>
> I don't see this message booting on a Hummingboard with HDMI
> disconnected.

I see this message in the following case:

- Boot the board with HDMI disconnected

- Connect the HDMI cable and then such message is displayed.

Thanks

mx6 hdmi resolution behaviour

[Russell King - ARM Linux]

On Tue, Jun 23, 2015 at 01:52:50PM -0300, Fabio Estevam wrote:
> On Tue, Jun 23, 2015 at 1:44 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> 
> > If you have no connected connectors, then you get 1024x768:
> >
> > imx-drm display-subsystem: No connectors reported connected with modes
> > [drm] Cannot find any crtc or sizes - going 1024x768
> >
> > as that's what DRM defaults to when it has no other timing information
> > available.
> 
> Agreed, but after the cable is connected we could try to find a more
> suitable timing?
> 
> >> [   16.310548] imx-ipuv3 2400000.ipu: videomode adapted for IPU restrictions
> >
> > I don't see this message booting on a Hummingboard with HDMI
> > disconnected.
> 
> I see this message in the following case:
> 
> - Boot the board with HDMI disconnected
> 
> - Connect the HDMI cable and then such message is displayed.

I've just tried this (the HBi1 was booted previously with the HDMI socket
disconnected).  Just now, I turned the TV on, and then connected it to
the HDMI.

The TV reported a resolution of 1024x768, and the kernel log was silent.

My guess would be that your HDMI sink is reporting slightly non-standard
1024x768 timings, which cause the IPU restrictions to be violated.  Maybe
dumping the EDID of the HDMI device would reveal this?

# edid-decode < /sys/class/drm/card0-HDMI-A-1/edid

might provide some hints?

-- 
FTTC broadband for 0.8mile line: currently@10.5Mbps down 400kbps up
according to speedtest.net.

mx6 hdmi resolution behaviour

[Fabio Estevam]

On Tue, Jun 23, 2015 at 5:41 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:

> I've just tried this (the HBi1 was booted previously with the HDMI socket
> disconnected).  Just now, I turned the TV on, and then connected it to
> the HDMI.

Thanks for testing it.

> The TV reported a resolution of 1024x768, and the kernel log was silent.

That's the point that makes me confused: shouldn't it report a higher
resolution like 1080p?

Why only 1024x768 even if the monitor supports higher resolution?

If we boot with the cable connected then it jumps to 1080.

> My guess would be that your HDMI sink is reporting slightly non-standard
> 1024x768 timings, which cause the IPU restrictions to be violated.  Maybe
> dumping the EDID of the HDMI device would reveal this?
>
> # edid-decode < /sys/class/drm/card0-HDMI-A-1/edid
>
> might provide some hints?

Thanks, will try it. Need to install this edid package in my rootfs.

mx6 hdmi resolution behaviour

[Russell King - ARM Linux]

On Tue, Jun 23, 2015 at 05:48:51PM -0300, Fabio Estevam wrote:
> On Tue, Jun 23, 2015 at 5:41 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> 
> > I've just tried this (the HBi1 was booted previously with the HDMI socket
> > disconnected).  Just now, I turned the TV on, and then connected it to
> > the HDMI.
> 
> Thanks for testing it.
> 
> > The TV reported a resolution of 1024x768, and the kernel log was silent.
> 
> That's the point that makes me confused: shouldn't it report a higher
> resolution like 1080p?

No - it won't go higher than the initial mode that was set.  See
drm_fb_helper_hotplug_event():

        max_width = fb_helper->fb->width;
        max_height = fb_helper->fb->height;

        drm_fb_helper_probe_connector_modes(fb_helper, max_width, max_height);

This calls connector->funcs->fill_modes with the max width/height,
which calls down into drm_helper_probe_single_connector_modes_merge_bits()
and there's limitations in there which means that we won't try to
increase the size of the framebuffer.

You do get that behaviour if you have the X server running, and that's
all down to the X server itself doing that (reacting to the hotplug
event which DRM generates.)

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

mx6 hdmi resolution behaviour

[Daniel Vetter]

On Tue, Jun 23, 2015 at 09:58:37PM +0100, Russell King - ARM Linux wrote:
> On Tue, Jun 23, 2015 at 05:48:51PM -0300, Fabio Estevam wrote:
> > On Tue, Jun 23, 2015 at 5:41 PM, Russell King - ARM Linux
> > <linux@arm.linux.org.uk> wrote:
> > 
> > > I've just tried this (the HBi1 was booted previously with the HDMI socket
> > > disconnected).  Just now, I turned the TV on, and then connected it to
> > > the HDMI.
> > 
> > Thanks for testing it.
> > 
> > > The TV reported a resolution of 1024x768, and the kernel log was silent.
> > 
> > That's the point that makes me confused: shouldn't it report a higher
> > resolution like 1080p?
> 
> No - it won't go higher than the initial mode that was set.  See
> drm_fb_helper_hotplug_event():
> 
>         max_width = fb_helper->fb->width;
>         max_height = fb_helper->fb->height;
> 
>         drm_fb_helper_probe_connector_modes(fb_helper, max_width, max_height);
> 
> This calls connector->funcs->fill_modes with the max width/height,
> which calls down into drm_helper_probe_single_connector_modes_merge_bits()
> and there's limitations in there which means that we won't try to
> increase the size of the framebuffer.
> 
> You do get that behaviour if you have the X server running, and that's
> all down to the X server itself doing that (reacting to the hotplug
> event which DRM generates.)

The initial fb allocated for fbdev emulation does indeed restrict what
fbdev/con will show. But it should in now way affect the mode list (that's
only the fbdev code doing the filtering there) or X. You should be able to
list/set 1080p. Might be useful to figure out with drm.debug whether the
mode was kicked out for some driver/hw restriction reason, that should get
logged.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

mx6 hdmi resolution behaviour

[Fabio Estevam]

On Tue, Jun 23, 2015 at 5:58 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:

>> That's the point that makes me confused: shouldn't it report a higher
>> resolution like 1080p?
>
> No - it won't go higher than the initial mode that was set.  See
> drm_fb_helper_hotplug_event():
>
>         max_width = fb_helper->fb->width;
>         max_height = fb_helper->fb->height;
>
>         drm_fb_helper_probe_connector_modes(fb_helper, max_width, max_height);
>
> This calls connector->funcs->fill_modes with the max width/height,
> which calls down into drm_helper_probe_single_connector_modes_merge_bits()
> and there's limitations in there which means that we won't try to
> increase the size of the framebuffer.

Got it, thanks for the clarification, Russell.