[PATCH 2/3] drm/i915/psr: Improve fast and IO wake lines calculation

[Jouni Högander]

Current fast and IO wake lines calculation is assuming fast wake sync
length is 18 pulses. Let's improve this by checking the actual length.

Also 10 us IO buffer wake time is currently assumed. This is not the case
with LunarLake and beyond. Fix this by adding getter for IO wake time and
return values there according to Bspec.

Bspec: 65450

Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
---
 drivers/gpu/drm/i915/display/intel_psr.c | 40 +++++++++++++++++++-----
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index 72cadad09db5..4a1e07411716 100644
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -1150,6 +1150,28 @@ static bool _lnl_compute_alpm_params(struct intel_dp *intel_dp,
 	return true;
 }
 
+/*
+ * From Bspec:
+ *
+ * For Xe2 and beyond
+ * RBR 15us, HBR1 11us, higher rates 10us
+ *
+ * For pre-Xe2
+ * 10 us
+ */
+static int get_io_wake_time(struct intel_dp *intel_dp,
+			struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+
+	if (DISPLAY_VER(i915) < 20 || crtc_state->port_clock > 270000)
+		return 10;
+	else if (crtc_state->port_clock > 162000)
+		return 11;
+	else
+		return 15;
+}
+
 static bool _compute_alpm_params(struct intel_dp *intel_dp,
 				 struct intel_crtc_state *crtc_state)
 {
@@ -1157,13 +1179,17 @@ static bool _compute_alpm_params(struct intel_dp *intel_dp,
 	int io_wake_lines, io_wake_time, fast_wake_lines, fast_wake_time;
 	u8 max_wake_lines;
 
-	if (DISPLAY_VER(i915) >= 12) {
-		io_wake_time = 42;
-		/*
-		 * According to Bspec it's 42us, but based on testing
-		 * it is not enough -> use 45 us.
-		 */
-		fast_wake_time = 45;
+	if (intel_dp->get_aux_fw_sync_len) {
+		int io_wake_time = get_io_wake_time(intel_dp, crtc_state);
+		int tfw_exit_latency = 20; /* eDP spec */
+		int phy_wake = 4;	   /* eDP spec */
+		int preamble = 8;	   /* eDP spec */
+		int precharge = intel_dp->get_aux_fw_sync_len() - preamble;
+
+		io_wake_time = max(precharge, io_wake_time) + preamble +
+			phy_wake + tfw_exit_latency;
+		fast_wake_time = precharge + preamble + phy_wake +
+			tfw_exit_latency;
 
 		/* TODO: Check how we can use ALPM_CTL fast wake extended field */
 		max_wake_lines = 12;
-- 
2.34.1