Re: [PATCH v2 2/2] drm/i915/vlv: Reset the ADPA in vlv_display_power_well_init()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Apr 15, 2016 at 03:40:10PM -0400, Lyude wrote:
> While VGA hotplugging worked(ish) before, it looks like that was mainly
> because we'd unintentionally enable it in
> valleyview_crt_detect_hotplug() when we did a force trigger. This
> doesn't work reliably enough because whenever the display powerwell on
> vlv gets disabled, the values set in VLV_ADPA get cleared and
> consequently VGA hotplugging gets disabled. This causes bugs such as one
> we found on an Intel NUC, where doing the following sequence of
> hotplugs:
> 
>       - Disconnect all monitors
>       - Connect VGA
>       - Disconnect VGA
>       - Connect HDMI
> 
> Would result in VGA hotplugging becoming disabled, due to the powerwells
> getting toggled in the process of connecting HDMI.
> 
> Changes since v1:
>  - Instead of handling the register writes ourself, we just reuse
>    intel_crt_detect()
>  - Instead of resetting the ADPA during display IRQ installation, we now
>    reset them in vlv_display_power_well_init()
> 
> CC: stable@vger.kernel.org
> Signed-off-by: Lyude <cpaul@redhat.com>
> ---
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 80e8bd4..c7d195f 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -902,6 +902,7 @@ static bool vlv_power_well_enabled(struct drm_i915_private *dev_priv,
>  
>  static void vlv_display_power_well_init(struct drm_i915_private *dev_priv)
>  {
> +	struct drm_encoder *encoder, *vga_encoder = NULL;
>  	enum pipe pipe;
>  
>  	/*
> @@ -935,6 +936,17 @@ static void vlv_display_power_well_init(struct drm_i915_private *dev_priv)
>  
>  	intel_hpd_init(dev_priv);
>  
> +	/* Re-enable the ADPA, if we have one */
> +	drm_for_each_encoder(encoder, dev_priv->dev) {
> +		if (encoder->encoder_type == DRM_MODE_ENCODER_DAC) {
> +			vga_encoder = encoder;
> +			break;
> +		}
> +	}
> +
> +	if (vga_encoder && vga_encoder->funcs->reset)
> +		vga_encoder->funcs->reset(vga_encoder);
> +

Something like

struct intel_encoder *encoder;
...
for_each_intel_encoder(encoder) {
	if (encoder->type == ANALOG)
		intel_crt_reset(&encoder->base);
}

would be neater in my eyes.

>  	i915_redisable_vga_power_on(dev_priv->dev);
>  }
>  
> -- 
> 2.5.5

-- 
Ville Syrj�l�
Intel OTC