Re: [PATCH v2] drm/i915/lspcon: Enable AUX interrupts for resume time initialization

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

On Tue, Nov 29, 2016 at 09:40:29PM +0200, Imre Deak wrote:
> For LSPCON initialization during system resume we need AUX
> functionality, but we call the corresponding encoder reset hook with all
> interrupts disabled. Without interrupts we'll do a poll-wait for AUX
> transfer completions, which adds a significant delay if the transfers
> timeout/need to be retried for some reason.
> 
> Fix this by enabling interrupts before calling the reset hooks. Note
> that while this will enable AUX interrupts it will keep HPD interrupts
> disabled, in a similar way to the init time output setup code.
> 
> This issue existed since LSPCON support was added.
> 
> v2:
> - Rebased on drm-tip.
> 
> Cc: Shashank Sharma <shashank.sharma@intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 8dac298..2cea2ef 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1582,18 +1582,21 @@ static int i915_drm_resume(struct drm_device *dev)
>  	intel_opregion_setup(dev_priv);
>  
>  	intel_init_pch_refclk(dev_priv);
> -	drm_mode_config_reset(dev);
>  
>  	/*
>  	 * Interrupts have to be enabled before any batches are run. If not the
>  	 * GPU will hang. i915_gem_init_hw() will initiate batches to
>  	 * update/restore the context.
>  	 *
> +	 * drm_mode_config_reset() needs AUX interrupts.
> +	 *
>  	 * Modeset enabling in intel_modeset_init_hw() also needs working
>  	 * interrupts.
>  	 */
>  	intel_runtime_pm_enable_interrupts(dev_priv);
>  
> +	drm_mode_config_reset(dev);
> +

Didn't look like anything should seriously explode.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

There is a slight concern on g4x/vlv/chv that an AUX interrupts would
trigger the hpd irq handler, which doesn't realize it's supposed to
ignore the actual hpd bits in PORT_HOTPLUG_STAT. So any aux before we
enable hpd processing for real could do something bad. So I guess we
should add some kind of software tracking for that stuff like we have
for PIPESTAT.

>  	mutex_lock(&dev->struct_mutex);
>  	if (i915_gem_init_hw(dev)) {
>  		DRM_ERROR("failed to re-initialize GPU, declaring wedged!\n");
> -- 
> 2.5.0
> 
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-- 
Ville Syrjälä
Intel OTC
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