Re: [PATCH] drm/i915: Fix the HDMI hot plug disconnection failure (v4)

[Chris Chiu <chiu@endlessm.com>]

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On Thu, Nov 29, 2018 at 9:52 AM Guang Bai <guang.bai@intel.com> wrote:

> On some GEN9 platforms, slowly unplugging (wiggling) the HDMI cable makes
> the kernel to believe the HDMI display is still connected. This is because
> the HDMI DDC lines are disconnected a little bit later after the hot-plug
> interrupt triggered thus an immediate edid fetch can be made. This problem
> has been identified by more than one customer recently. Use digital
> port live states to authorize the edid read at HDMI detection point will
> ensure most of the display related software states updated and rest of them
> will be renewed accordingly when the port is connected.
>
> v2: Fix the formatting issue
> v3: Use digital port states to authorize the edid read
> v4: Add comments on issue histories and rationale of the fix (Chris W)
>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Chris Chiu <chiu@endlessm.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Guang Bai <guang.bai@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> b/drivers/gpu/drm/i915/intel_hdmi.c
> index e2c6a2b..8cf7c78 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1929,7 +1929,7 @@ intel_hdmi_detect(struct drm_connector *connector,
> bool force)
>
>         intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
>
> -       if (IS_ICELAKE(dev_priv) &&
> +       if ((IS_ICELAKE(dev_priv) || IS_GEN9_BC(dev_priv)) &&
>             !intel_digital_port_connected(encoder))
>                 goto out;
>
> --
> 2.7.4
>
>
I've tried on my problematic ASUS X705FD, seems no problem on my test
scenarios (100% pass). I can reproduce with very slow unplug on previous
versions but can't reproduce anymore on this one. I tried slow unplgug with
few finds of HDMI jack I have in hand, it responds as expected.

Don't know if there's any tough test case I should try, but I think it
pretty
much solve the problem. Thanks.

Chris

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