[PATCH 1/9] drm/i915/wm: Reject SAGV consistently when block_time_us==0

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

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We have three ways for the platform to indicate that
SAGV is not supported:
- pcode returns zero block time
- pcode returns only a single QGV point (icl+)
- pcode rejects the SAGV enable/disable command (pre-icl)

We don't currently consider all those factors when computing
pipe_sagv_reject, meaning we might still try to enable
SAGV when we should not.

I think one plausible scenario is when pcode returns a
zero block time, and all the pipes are disabled. In
that case intel_crtc_can_enable_sagv() will return true
for all pipes, and thus we might try to enable SAGV
despite pcode indicating that it's not supported.

Make sure pipe_sagv_reject will consistently reject
SAGV when our cached block time is zero. That will cover
all the aforementioned mechanisms by which SAGV can be
disabled.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/skl_watermark.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c b/drivers/gpu/drm/i915/display/skl_watermark.c
index d45b3bcc6ef0..09988f46e083 100644
--- a/drivers/gpu/drm/i915/display/skl_watermark.c
+++ b/drivers/gpu/drm/i915/display/skl_watermark.c
@@ -308,9 +308,6 @@ static bool skl_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
 	enum plane_id plane_id;
 	int max_level = INT_MAX;
 
-	if (!intel_has_sagv(display))
-		return false;
-
 	if (!crtc_state->hw.active)
 		return true;
 
@@ -377,6 +374,9 @@ bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_display *display = to_intel_display(crtc_state);
 
+	if (!display->sagv.block_time_us)
+		return false;
+
 	if (!display->params.enable_sagv)
 		return false;
 
-- 
2.52.0