imx6: i2c-transfer timeout issue after resume

[Pintu Agarwal]

On Fri, Oct 4, 2019 at 3:47 PM Pintu Agarwal <pintu.ping at gmail.com> wrote:
>
> Hi,
>
> On Sun, Sep 29, 2019 at 10:24 PM Pintu Agarwal <pintu.ping at gmail.com> wrote:
> >
> > >
> > > On Mon, Sep 23, 2019 at 1:28 PM Pintu Agarwal <pintu.ping at gmail.com> wrote:
> > > >
> > > > Dear Philipp,
> > > >
> > > > I have a iMX6dl custom board with custom Linux Kernel 4.8.
> > > > I have both LCD and HDMI connected to the board.
> > > > And we are using weston/wayland as the display interface.
> > > > In normal boot, both LCD and HDMI display is working fine.
> > > >
> > > > But, currently, for one of the requirement, I am trying to explore and
> > > > support hibernation image booting on it.
> > > > Currently, we are able to resume the system without display.
> > > > Also, if we make the entire imx-drm as modules, and then install the
> > > > modules after resume, even LCD is also coming up.
> > > > But HDMI display is black out.
> > > >
>
> I just found the main root cause of the HDMI screen blackout issue
> after system resume.
> * HDMI is trying to get EDID data from the monitor using I2C interface.
> * But its seems i2c_transfer is getting timeout after 5 retries.
> * Thus EDID data is failing, and HDMI could not able to detect the monitor.
>
> This is the logs:
>
> [  441.104989] [drm:drm_helper_probe_single_connector_modes]
> [CONNECTOR:29:HDMI-A-1] status updated from unknown to connected
> [  441.116080]: drm_helper_probe_single_connector_modes - inside -
> else override_edid
> [  441.124416]: drm_helper_probe_single_connector_modes - inside -
> else - drm_load_edid_firmware: count: 0
> [  441.134546]: drm_helper_probe_single_connector_modes - calling - get_modes
> [  441.142157]: dw_hdmi_connector_get_modes : called
> [  441.147652]: dw_hdmi_connector_get_modes : called - calling -> drm_get_edid
> [  441.155346]: drm_do_probe_ddc_edid : called!
> [  441.660759]: drm_do_probe_ddc_edid : i2c_transfer: ret: -110, retry: 5
> [  442.170758]: drm_do_probe_ddc_edid : i2c_transfer: ret: -110, retry: 4
> [  442.680755]: drm_do_probe_ddc_edid : i2c_transfer: ret: -110, retry: 3
> [  443.190755]: drm_do_probe_ddc_edid : i2c_transfer: ret: -110, retry: 2
> [  443.700754]: drm_do_probe_ddc_edid : i2c_transfer: ret: -110, retry: 1
> [  443.707989]: drm_get_edid : called - drm_probe_ddc - failed
> [  443.714303] dwhdmi-imx 120000.hdmi: failed to get edid
>
> Is there any clue, how to resolve this i2c failure issue, after resume?
> This does not happen in normal booting case.
>
> These are the steps I follow:
> * Boot the system normally (without display) and install all imx-drm as modules.
> * Then uninstall the modules in reverse order.
> * Take the snapshot of the system (suspend to disk).
> * Reboot the system and boot with the image.
> * Install all the modules again.
> * Then launch the Weston.
> * During the weston launch in the beginning we observe this error.
>

* Changing the subject to be more relevant.

I need some pointers in debugging this i2c_transfer timeout issue,
after system resume.
I am not so much familiar with i2c, so I am looking for some clue here.

i2c-experts (or pm experts), please help me to find the root cause and
debug further.

Thanks,
Pintu