DVI output on i.MX51 EVP board not working?

DVI output on i.MX51 EVP board not working?

[Wladimir J. van der Laan]

Hello,

I can't get the DVI output to work on a i.MX51 EVP board (babbage). There
seems to be no signal at all. The board is running the mainline kernel 4.11.0-rc4 as of a
day ago (89970a0).

- The connector and cable works. u-boot (v2016.07-rc2) shows a penguin at boot.
  However while the Linux kernel boots, the signal goes away: monitor (a fairly
  old Dell 24" panel, max resolution 1600x1200, works fine with Linux/DRM with other
  hardware) goes to sleep mode.

- Monitor is connected through HDMI<->DVI cable, could try another monitor if
  that's potentially the issue (Could it be EDID related? I'd guess not as the timings
  are hardcoded in the device tree).

- Haven't changed anything in the dtb with regard to port config or resolution
  or timings. The default ones in imx51-babbage.dts should theoretically just
  work. I checked and these are the same as in u-boot:

        timing0: dvi {
                clock-frequency = <65000000>;
                hactive = <1024>;
                vactive = <768>;
                hback-porch = <220>;
                hfront-porch = <40>;
                vback-porch = <21>;
                vfront-porch = <7>;
                hsync-len = <60>;
                vsync-len = <10>;
        };

- Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
  dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
  bisect, unfortunately.

- In dmesg this is all the output I get:

[    0.801700] imx-ipuv3 40000000.ipu: no port@0 node in /soc/ipu@40000000, not using CSI0
[    0.809826] imx-ipuv3 40000000.ipu: no port@1 node in /soc/ipu@40000000, not using CSI1
[    0.818600] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[    0.825230] [drm] No driver support for vblank timestamp query.
[    0.831481] imx-drm display-subsystem: bound imx-ipuv3-crtc.0 (ops ipu_crtc_ops)
[    0.839132] imx-drm display-subsystem: bound imx-ipuv3-crtc.1 (ops ipu_crtc_ops)
[    0.846617] imx-drm display-subsystem: bound display@di0 (ops imx_pd_ops)
[    0.986410] Console: switching to colour frame buffer device 128x48
[    1.032306] imx-drm display-subsystem: fb0:  frame buffer device
[    1.039362] [drm] Initialized imxdrm 1.0.0 20120507 for display-subsystem on minor 0
[    1.047276] imx-ipuv3 40000000.ipu: IPUv3EX probed

As far as I know this is nothing unexpected. CSI0 and CSI1 are not connected but DI0 should be the
DVI port, which does get initialized. The size of the framebuffer device seems to indicate the resolution
is set correctly (assuming 16x8 characters).

There was also a "timeout waiting for vsync" error, 

[    0.917254] WARNING: CPU: 0 PID: 1 at drivers/gpu/drm/drm_atomic_helper.c:1122 drm_atomic_helper_wait_for_vblanks.part.0+0x264/0x274
[    0.917259] [CRTC:26] vblank wait timed out

which was fixed after applying Philipp Zabel's "drm/imx: don't wait for vblank and stop calling cleanup_planes in commit_tail" patch series.
However that didn't solve the output issue.

I'm out of things to try to diagnose this, does anyone perhaps have an idea or seen this issue
before?

Regards,
Wladimir van der Laan
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Re: DVI output on i.MX51 EVP board not working?

[Philipp Zabel]

Hi Wladimir,

On Fri, 2017-03-31 at 07:36 +0200, Wladimir J. van der Laan wrote:
> Hello,
> 
> I can't get the DVI output to work on a i.MX51 EVP board (babbage). There
> seems to be no signal at all. The board is running the mainline kernel 4.11.0-rc4 as of a
> day ago (89970a0).
> 
> - The connector and cable works. u-boot (v2016.07-rc2) shows a penguin at boot.
>   However while the Linux kernel boots, the signal goes away: monitor (a fairly
>   old Dell 24" panel, max resolution 1600x1200, works fine with Linux/DRM with other
>   hardware) goes to sleep mode.
> 
> - Monitor is connected through HDMI<->DVI cable, could try another monitor if
>   that's potentially the issue (Could it be EDID related? I'd guess not as the timings
>   are hardcoded in the device tree).
> 
> - Haven't changed anything in the dtb with regard to port config or resolution
>   or timings. The default ones in imx51-babbage.dts should theoretically just
>   work. I checked and these are the same as in u-boot:
> 
>         timing0: dvi {
>                 clock-frequency = <65000000>;
>                 hactive = <1024>;
>                 vactive = <768>;
>                 hback-porch = <220>;
>                 hfront-porch = <40>;
>                 vback-porch = <21>;
>                 vfront-porch = <7>;
>                 hsync-len = <60>;
>                 vsync-len = <10>;
>         };
> 
> - Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
>   dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
>   bisect, unfortunately.

Looking at the hardware user's guide [1] chapter 9 (VGA and DVI out), I
notice that the TFP410PA bridge seems to be connected to the DISP2_DAT
data lines, but uses the DISP1_H/V sync signals (which I can't believe
is right), according to figure 9-1. But the device tree pin
configuration configures the DISP1_DAT data lines with pinctrl_ipu_disp1
instead. This pin configuration was moved there from imx51.dtsi, so I
think it was just never adapted for this boards' quirks.

[1] http://www.nxp.com/assets/documents/data/en/user-guides/evk_imx51_Hardware_UG.pdf

It might also be useful to find out which GPIOs are connected to the
TFP410 power down and reset lines.

> - In dmesg this is all the output I get:
> 
> [    0.801700] imx-ipuv3 40000000.ipu: no port@0 node in /soc/ipu@40000000, not using CSI0
> [    0.809826] imx-ipuv3 40000000.ipu: no port@1 node in /soc/ipu@40000000, not using CSI1
> [    0.818600] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [    0.825230] [drm] No driver support for vblank timestamp query.
> [    0.831481] imx-drm display-subsystem: bound imx-ipuv3-crtc.0 (ops ipu_crtc_ops)
> [    0.839132] imx-drm display-subsystem: bound imx-ipuv3-crtc.1 (ops ipu_crtc_ops)
> [    0.846617] imx-drm display-subsystem: bound display@di0 (ops imx_pd_ops)
> [    0.986410] Console: switching to colour frame buffer device 128x48
> [    1.032306] imx-drm display-subsystem: fb0:  frame buffer device
> [    1.039362] [drm] Initialized imxdrm 1.0.0 20120507 for display-subsystem on minor 0
> [    1.047276] imx-ipuv3 40000000.ipu: IPUv3EX probed
> 
> As far as I know this is nothing unexpected. CSI0 and CSI1 are not connected but DI0 should be the
> DVI port, which does get initialized. The size of the framebuffer device seems to indicate the resolution
> is set correctly (assuming 16x8 characters).
> 
> There was also a "timeout waiting for vsync" error, 
> 
> [    0.917254] WARNING: CPU: 0 PID: 1 at drivers/gpu/drm/drm_atomic_helper.c:1122 drm_atomic_helper_wait_for_vblanks.part.0+0x264/0x274
> [    0.917259] [CRTC:26] vblank wait timed out
> 
> which was fixed after applying Philipp Zabel's "drm/imx: don't wait for vblank and stop calling cleanup_planes in commit_tail" patch series.
> However that didn't solve the output issue.
> 
> I'm out of things to try to diagnose this, does anyone perhaps have an idea or seen this issue
> before?
> 
> Regards,
> Wladimir van der Laan
> 

regards
Philipp

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Re: DVI output on i.MX51 EVP board not working?

[Wladimir J. van der Laan]

Hello Philipp,

> Looking at the hardware user's guide [1] chapter 9 (VGA and DVI out), I
> notice that the TFP410PA bridge seems to be connected to the DISP2_DAT
> data lines, but uses the DISP1_H/V sync signals (which I can't believe
> is right), according to figure 9-1. But the device tree pin
> configuration configures the DISP1_DAT data lines with pinctrl_ipu_disp1
> instead. This pin configuration was moved there from imx51.dtsi, so I
> think it was just never adapted for this boards' quirks.

Interesting, thanks a lot for pointing that out.

The figure 1-3 on page 6 shows both Disp-1 and Disp-2 going to the DVI-I
connector, however the output of Disp-2 goes through the DAC so I suppose
that's for the VGA pins.

The figure 9-1 seems to be in conflict with that. DISP1_DAT isn't used at all
there, but DISP2_DAT (albeit different pin ranges) go to both the ADV7123 and
TFP410PA.

> It might also be useful to find out which GPIOs are connected to the
> TFP410 power down and reset lines.

Yes, indeed. Luckily it works in u-boot so that's a reference.

Regards,
Wladimir
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Re: DVI output on i.MX51 EVP board not working?

[Fabio Estevam]

Hi Wladimir,

On Fri, Mar 31, 2017 at 2:36 AM, Wladimir J. van der Laan
<laanwj@gmail.com> wrote:

> - Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
>   dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
>   bisect, unfortunately.

It was a long time I worked on this commit and it worked well for me
on an old DVI monitor.

I will try to locate such monitor in the office next week and try it again.

Regards,

Fabio Estevam
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Re: DVI output on i.MX51 EVP board not working?

[Wladimir J. van der Laan]

On Sat, Apr 01, 2017 at 06:40:52PM -0300, Fabio Estevam wrote:
> Hi Wladimir,
> 
> On Fri, Mar 31, 2017 at 2:36 AM, Wladimir J. van der Laan
> <laanwj@gmail.com> wrote:
> 
> > - Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
> >   dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
> >   bisect, unfortunately.
> 
> It was a long time I worked on this commit and it worked well for me
> on an old DVI monitor.

An extra data point: I tried with an older monitor (max 1280x1024) w/ DVI to
DVI cable, exactly the same behavior: u-boot shows output but "no signal" when
kernel boots. I was not able to go all the way back though, and only tested
this with mainline.

> I will try to locate such monitor in the office next week and try it again.

Thanks!

Regards,
Wladimir
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Re: DVI output on i.MX51 EVP board not working?

[Fabio Estevam]

On Sat, Apr 1, 2017 at 6:40 PM, Fabio Estevam <festevam@gmail.com> wrote:
> Hi Wladimir,
>
> On Fri, Mar 31, 2017 at 2:36 AM, Wladimir J. van der Laan
> <laanwj@gmail.com> wrote:
>
>> - Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
>>   dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
>>   bisect, unfortunately.
>
> It was a long time I worked on this commit and it worked well for me
> on an old DVI monitor.
>
> I will try to locate such monitor in the office next week and try it again.

Finally had a chance to test it and I can see both U-Boot logo and
kernel penguin correctly on my monitor.
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Re: DVI output on i.MX51 EVP board not working?

[Wladimir J. van der Laan]

On Wed, Apr 05, 2017 at 09:50:23AM -0300, Fabio Estevam wrote:
> On Sat, Apr 1, 2017 at 6:40 PM, Fabio Estevam <festevam@gmail.com> wrote:
> > Hi Wladimir,
> >
> > On Fri, Mar 31, 2017 at 2:36 AM, Wladimir J. van der Laan
> > <laanwj@gmail.com> wrote:
> >
> >> - Went as far back as kernel v4.0, even to v3.12 or so (commit 493a863, "ARM:
> >>   dts: imx51-babbage: Make DVI and WVGA panel functional"). No difference. So nothing to
> >>   bisect, unfortunately.
> >
> > It was a long time I worked on this commit and it worked well for me
> > on an old DVI monitor.
> >
> > I will try to locate such monitor in the office next week and try it again.
> 
> Finally had a chance to test it and I can see both U-Boot logo and
> kernel penguin correctly on my monitor.

Ok, thanks for testing.

To be clear: was this result with v3.x, or with mainline?

Regards,
Wladimir
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Re: DVI output on i.MX51 EVP board not working?

[Fabio Estevam]

On Wed, Apr 5, 2017 at 10:05 AM, Wladimir J. van der Laan
<laanwj@gmail.com> wrote:

> Ok, thanks for testing.
>
> To be clear: was this result with v3.x, or with mainline?

I tested with 4.11-rc5 and the kernel is driving the DVI monitor correctly.
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