[Intel-gfx] [PATCH 08/12] drm/i915: Skip dpcd/edid read unless there was a long hpd

[Chris Wilson]

On Thu, Jul 28, 2016 at 05:50:44PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Supposedly nothing should have change in the DPCD/EDID deparment unless
> there was a long HPD. Let's skip the work in ->detect() in that case.
> We'll still want to do the link status check thouhg.
> 
> Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
> Cc: Jim Bride <jim.bride at linux.intel.com>
> Cc: Manasi D Navare <manasi.d.navare at intel.com>
> Cc: Durgadoss R <durgadoss.r at intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 19 +++++++++++++++----
>  drivers/gpu/drm/i915/intel_drv.h |  2 +-
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 675b83f57a07..d1dd351682d2 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4315,12 +4315,15 @@ intel_dp_detect(struct drm_connector *connector, bool force)
>  {
>  	struct intel_dp *intel_dp = intel_attached_dp(connector);
>  	struct intel_connector *intel_connector = to_intel_connector(connector);
> -	enum drm_connector_status status;
> +	enum drm_connector_status status = connector->status;
>  
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
> -	status = intel_dp_long_pulse(intel_connector);
> +	if (intel_dp->long_hpd_pending) {

Set from a worker unlocked, consumed unlocked. At the very least you
want a WRITE_ONCE() to document this should be unset before
intel_dp_long_pulse(), if (cmpxchg(long_hpd_pending, 1, 0) {} and a
smp_store_mb() when setting for belt-and-braces approach.

> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 7fef18288aa2..20cf7ad26357 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -854,7 +854,7 @@ struct intel_dp {
>  	uint8_t sink_count;
>  	bool link_mst;
>  	bool has_audio;
> -	bool detect_done;

Unrelated cleanup?

> +	bool long_hpd_pending;
>  	enum hdmi_force_audio force_audio;
>  	bool limited_color_range;
>  	bool color_range_auto;

-- 
Chris Wilson, Intel Open Source Technology Centre