Re: [PATCH] drm/i915: Restrict usage of live status check

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 17 Mar 2016, Shashank Sharma <shashank.sharma@intel.com> wrote:
> [ text/plain ]
> This patch restricts usage of live status check for HDMI detection.
> While testing certain (monitor + cable) combinations with various
> intel  platforms, it seems that live status register is not reliable
> on some older devices. So limit the live_status check from VLV onwards.
>
> This fixes a regression introduced in:
> 	commit: 237ed86 "drm/i915: Check live status"
> 	Author: Sonika Jindal <sonika.jindal@intel.com>
> 	Date:   Tue Sep 15 09:44:20 2015 +0530
>

Fixes: 237ed86c693d ("drm/i915: Check live status before reading edid")
Cc: stable@vger.kernel.org # v4.4
Bugzilla: ?

> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index e2dab48..d24d18a 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1397,7 +1397,8 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
>  	enum drm_connector_status status;
>  	struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
>  	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> -	bool live_status = false;
> +	struct drm_device *dev = connector->dev;

This is unnecessary.

> +	bool live_status = true;
>  	unsigned int try;
>  
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> @@ -1405,16 +1406,21 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
>  
>  	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
>  
> -	for (try = 0; !live_status && try < 9; try++) {
> -		if (try)
> -			msleep(10);
> -		live_status = intel_digital_port_connected(dev_priv,
> +	/*
> +	* Live status check for HDMI detection is not very
> +	* reliable on older platforms. So insist the live
> +	* status check for EDID read from VLV onwards.
> +	*/
> +	if (INTEL_INFO(dev)->gen >= 7 && !IS_IVYBRIDGE(dev)) {

Replace dev with dev_priv. Both work, it's magic, but we prefer using
dev_priv where possible.

Move try variable declaration here.

> +		for (try = 0; !live_status && try < 9; try++) {

You'll now ignore live_status on all platforms. (But please do not turn
this into a do-while, keep it as a for loop.)

> +			if (try)
> +				msleep(10);
> +			live_status = intel_digital_port_connected(dev_priv,
>  				hdmi_to_dig_port(intel_hdmi));
> +		}
> +		DRM_DEBUG_KMS("Live status %s\n", live_status ? "up" : "down");

Consider using onoff(live_status) instead of live_status ? "up" :
"down".

>  	}
>  
> -	if (!live_status)
> -		DRM_DEBUG_KMS("Live status not up!");
> -
>  	intel_hdmi_unset_edid(connector);
>  
>  	if (intel_hdmi_set_edid(connector, live_status)) {

-- 
Jani Nikula, Intel Open Source Technology Center
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