[Intel-gfx] [PATCH v3 2/2] drm/i915/dp: Helper to check for DDI BUF status to get active

[Manasi Navare]

Based on the platform, Bspec expects us to wait or poll with
timeout for DDI BUF IDLE bit to be set to 0 (non idle) or get active
after enabling DDI_BUF_CTL.

v3:
* Add a new function _active for DDI BUF CTL to be non idle (Ville)
v2:
* Based on platform, fixed delay or poll (Ville)
* Use a helper to do this (Imre, Ville)

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 7d5c8ab88fc4..ff6b1e9d1b4e 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -1195,6 +1195,20 @@ static void intel_wait_ddi_buf_idle(struct drm_i915_private *dev_priv,
 			port_name(port));
 }
 
+static void intel_wait_ddi_buf_active(struct drm_i915_private *dev_priv,
+				      enum port port)
+{
+	if (INTEL_GEN(dev_priv) <= 9) {
+		usleep_range(600, 1000);
+		return;
+	}
+
+	if (wait_for_us(!(intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
+			  DDI_BUF_IS_IDLE), 600))
+		drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c to get active\n",
+			port_name(port));
+}
+
 static u32 hsw_pll_to_ddi_pll_sel(const struct intel_shared_dpll *pll)
 {
 	switch (pll->info->id) {
@@ -4020,7 +4034,7 @@ static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp)
 	intel_de_write(dev_priv, DDI_BUF_CTL(port), intel_dp->DP);
 	intel_de_posting_read(dev_priv, DDI_BUF_CTL(port));
 
-	udelay(600);
+	intel_wait_ddi_buf_active(dev_priv, port);
 }
 
 static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
-- 
2.19.1