Re: [PATCH v4 08/17] drm/i915: Add distrust_bios_wm flag to dev_priv

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 10-05-16 om 03:21 schreef Matt Roper:
> SKL-style platforms can't fully trust the watermark/DDB settings
> programmed by the BIOS and need to do extra sanitization on their first
> atomic update.  Add a flag to dev_priv that is set during hardware
> readout and cleared at the end of the first commit.
>
> Note that for the somewhat common case where everything is turned off
> when the driver starts up, we don't need to bother with a recompute...we
> know exactly what the DDB should be (all zero's) so just setup the DDB
> directly in that case.
>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      |  7 +++++++
>  drivers/gpu/drm/i915/intel_display.c |  7 +++++++
>  drivers/gpu/drm/i915/intel_pm.c      | 15 ++++++++++++++-
>  3 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index a67462a..27aaaca 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1993,6 +1993,13 @@ struct drm_i915_private {
>  		 * cstate->wm.need_postvbl_update.
>  		 */
>  		struct mutex wm_mutex;
> +
> +		/*
> +		 * Set during HW readout of watermarks/DDB.  Some platforms
> +		 * need to know when we're still using BIOS-provided values
> +		 * (which we don't fully trust).
> +		 */
> +		bool distrust_bios_wm;
>  	} wm;
>  
>  	struct i915_runtime_pm pm;
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7acdfa3..3028bf4 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13703,6 +13703,13 @@ static int intel_atomic_commit(struct drm_device *dev,
>  			dev_priv->display.optimize_watermarks(intel_cstate);
>  	}
>  
> +	/*
> +	 * We've now finished at least one atomic commit following hw readout,
> +	 * so any platforms that needed to do extra sanitization of watermarks
> +	 * should have done it by now.
> +	 */
> +	dev_priv->wm.distrust_bios_wm = false;
I guess at this point atomic wm commit doesn't work yet?

When it does it should be put after swap_state, or kill it and rely on skip_intermediate_wm. :)
>  	for_each_crtc_in_state(state, crtc, old_crtc_state, i) {
>  		intel_post_plane_update(to_intel_crtc_state(old_crtc_state));
>  
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 90ba05c..e3877dc 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4021,11 +4021,24 @@ void skl_wm_get_hw_state(struct drm_device *dev)
>  	struct skl_ddb_allocation *ddb = &dev_priv->wm.skl_hw.ddb;
>  	struct drm_crtc *crtc;
>  	struct intel_crtc *intel_crtc;
> +	bool any_on = false;
>  
>  	skl_ddb_get_hw_state(dev_priv, ddb);
> -	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>  		skl_pipe_wm_get_hw_state(crtc);
>  
> +		if (crtc->state->active)
> +			any_on = true;
> +	}
> +
dev_priv->active_crtcs?

> +	if (any_on) {
> +		/* Fully recompute DDB on first atomic commit */
> +		dev_priv->wm.distrust_bios_wm = true;
> +	} else {
> +		/* Easy/common case; just sanitize DDB now if everything off */
> +		memset(ddb, 0, sizeof(*ddb));
> +	}
> +
>  	/* Calculate plane data rates */
>  	for_each_intel_crtc(dev, intel_crtc) {
>  		struct intel_crtc_state *cstate = intel_crtc->config;


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