[Intel-gfx] [PATCH v6 2/8] drm/i915/bxt: IPC WA for Broxton

[Mahesh Kumar]

If IPC is enabled in BXT, display underruns are observed.
WA: The Line Time programmed in the WM_LINETIME register should be
half of the actual calculated Line Time.

Programmed Line Time = 1/2*Calculated Line Time

Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c |  2 ++
 drivers/gpu/drm/i915/i915_drv.h |  2 ++
 drivers/gpu/drm/i915/intel_pm.c | 11 +++++++++--
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 445fec9..1b0a589 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1243,6 +1243,8 @@ int i915_driver_load(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	intel_runtime_pm_enable(dev_priv);
 
+	dev_priv->ipc_enabled = false;
+
 	/* Everything is in place, we can now relax! */
 	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
 		 driver.name, driver.major, driver.minor, driver.patchlevel,
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 63c0ea0..6691a4e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2128,6 +2128,8 @@ struct drm_i915_private {
 	/* perform PHY state sanity checks? */
 	bool chv_phy_assert[2];
 
+	bool ipc_enabled;
+
 	/* Used to save the pipe-to-encoder mapping for audio */
 	struct intel_encoder *av_enc_map[I915_MAX_PIPES];
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 8908736..7090a7c 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3769,7 +3769,10 @@ skl_compute_wm_level(const struct drm_i915_private *dev_priv,
 static uint32_t
 skl_compute_linetime_wm(struct intel_crtc_state *cstate)
 {
+	struct drm_atomic_state *state = cstate->base.state;
+	struct drm_i915_private *dev_priv = to_i915(state->dev);
 	uint32_t pixel_rate;
+	uint32_t linetime_wm;
 
 	if (!cstate->base.active)
 		return 0;
@@ -3779,8 +3782,12 @@ skl_compute_linetime_wm(struct intel_crtc_state *cstate)
 	if (WARN_ON(pixel_rate == 0))
 		return 0;
 
-	return DIV_ROUND_UP(8 * cstate->base.adjusted_mode.crtc_htotal * 1000,
-			    pixel_rate);
+	linetime_wm = DIV_ROUND_UP(8 * cstate->base.adjusted_mode.crtc_htotal *
+						1000, pixel_rate);
+	if (IS_BROXTON(dev_priv) && dev_priv->ipc_enabled)
+		linetime_wm = DIV_ROUND_UP(linetime_wm, 2);
+
+	return linetime_wm;
 }
 
 static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
-- 
2.10.1