[Intel-gfx] [PATCH] drm/i915: Restrict usage of live status check

[Ville Syrjälä]

On Thu, Mar 10, 2016 at 05:05:47PM +0530, Shashank Sharma wrote:
> This patch does the following:
> - 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
>   doesn't work reliably on some older devices. So limit the
>   live_status check for HDMI detection, only for platforms
>   from gen7 onwards.

Not good enough. We have regressions reported on IVB at least.
Also I'm not convinced more recent platforms are any necessarily
better here.

> - Cleans up the retry logic.
>   There is an extra 'if (try)' check, which can be avoided by
>   changing the logic slightly, keeping the delay as same(80ms)

I wouldn't call a goto loop clean.

> 
> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index e2dab48..3f6db91 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1397,24 +1397,31 @@ 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;
> -	unsigned int try;
> +	bool live_status = true;
> +	unsigned int try = 9;
>  
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
>  	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
>  
> -	for (try = 0; !live_status && try < 9; try++) {
> -		if (try)
> -			msleep(10);
> +	/*
> +	 * When tested with specific set of monitors + cables,
> +	 * live status behavior is not very consistent for older
> +	 * platforms. So add live status check from GEN7
> +	 * onwards.
> +	 */
> +	if (INTEL_INFO(dev_priv->dev)->gen >= 7) {
> +retry_ls:
>  		live_status = intel_digital_port_connected(dev_priv,
>  				hdmi_to_dig_port(intel_hdmi));
> +		if (!live_status && --try) {
> +			msleep(10);
> +			goto retry_ls;
> +		}
> +		DRM_DEBUG_KMS("Live status %s!\n", 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)) {
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC