Re: [PATCH] drm/i915: get power domain in case the BIOS enabled eDP VDD

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Apr 09, 2014 at 06:47:33PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> 
> If I unplug the eDP monitor, the BIOS of my machine will enable the
> VDD bit, then when the driver loads it will think VDD is enabled. It
> will detect that the eDP is not enabled and return false from
> intel_edp_init_connector. This will trigger a call to
> edp_panel_vdd_off_sync(), which trigger a WARN saying that the
> refcount of the power domain is less than zero.
> 
> The problem happens because the driver gets a refcount whenever it
> enables the VDD bit, and puts the refcount whenever it disables the
> VDD bit. But on this case, the BIOS enabled VDD, so all we do is to
> call put() without calling get() first, so the code added is there to
> make sure we always have the get() in case the BIOS enabled the bit.
> 
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

Is this the bug reported by Chris on irc yesterday? Chris?
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index e48d47c..a432904 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3638,7 +3638,8 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  {
>  	struct drm_connector *connector = &intel_connector->base;
>  	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> -	struct drm_device *dev = intel_dig_port->base.base.dev;
> +	struct intel_encoder *intel_encoder = &intel_dig_port->base;
> +	struct drm_device *dev = intel_encoder->base.dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_display_mode *fixed_mode = NULL;
>  	bool has_dpcd;
> @@ -3648,6 +3649,14 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	if (!is_edp(intel_dp))
>  		return true;
>  
> +	/* The VDD bit needs a power domain reference, so if the bit is already
> +	 * enabled when we boot, grab this reference. */
> +	if (edp_have_panel_vdd(intel_dp)) {
> +		enum intel_display_power_domain power_domain;
> +		power_domain = intel_display_port_power_domain(intel_encoder);
> +		intel_display_power_get(dev_priv, power_domain);
> +	}
> +
>  	/* Cache DPCD and EDID for edp. */
>  	intel_edp_panel_vdd_on(intel_dp);
>  	has_dpcd = intel_dp_get_dpcd(intel_dp);
> -- 
> 1.9.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch