[PATCH v3 3/5] drm/i915/psr: Calculate IO wake and fast wake lines for DISPLAY_VER < 12

[Jouni Högander]

Bspec mentions 50 us for IO wake time and 32 us for fast wake time. 32 us
is most probably wrong as it doesn't meet the specification as fast wake
time is calculated in Bspec like this:

10..16 us (precharge) + 8 us (preamble) + 4 us (phy_wake) + 20 us
(tfw_exit_latency)

Instead of using these constants calculate IO wake and fast wake for
DISPLAY_VER < 12 as well.

Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
---
 drivers/gpu/drm/i915/display/intel_psr.c | 31 ++++++++++++++++++------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index 905208e1c771..afcfa541942c 100644
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -1150,9 +1150,25 @@ static bool _lnl_compute_alpm_params(struct intel_dp *intel_dp,
 	return true;
 }
 
-static int get_io_buffer_wake_time(void)
+/*
+ * From Bspec:
+ *
+ * For DISPLAY_VER >= 12
+ * 10 us
+ *
+ * For DISPLAY_VER < 12
+ * This is not directly mentioned in Bspec. There are 50 us io wake time and 32
+ * us fast wake time. Clearly preharge pulses are not (improperly) included in
+ * 32 us fast wake time. 50 us - 32 us = 18 us.
+ */
+static int get_io_buffer_wake_time(const struct intel_crtc_state *crtc_state)
 {
-	return 10;
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+
+	if (DISPLAY_VER(i915) < 12)
+		return 18;
+	else
+		return 10;
 }
 
 static bool _compute_alpm_params(struct intel_dp *intel_dp,
@@ -1162,8 +1178,8 @@ 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) {
-		int io_buffer_wake_time = get_io_buffer_wake_time();
+	if (DISPLAY_VER(i915) >= 9) {
+		int io_buffer_wake_time = get_io_buffer_wake_time(crtc_state);
 		int tfw_exit_latency = 20; /* eDP spec */
 		int phy_wake = 4;	   /* eDP spec */
 		int preamble = 8;	   /* eDP spec */
@@ -1173,14 +1189,13 @@ static bool _compute_alpm_params(struct intel_dp *intel_dp,
 			phy_wake + tfw_exit_latency;
 		fast_wake_time = precharge + preamble + phy_wake +
 			tfw_exit_latency;
+	}
 
+	if (DISPLAY_VER(i915) >= 12)
 		/* TODO: Check how we can use ALPM_CTL fast wake extended field */
 		max_wake_lines = 12;
-	} else {
-		io_wake_time = 50;
-		fast_wake_time = 32;
+	else
 		max_wake_lines = 8;
-	}
 
 	io_wake_lines = intel_usecs_to_scanlines(
 		&crtc_state->hw.adjusted_mode, io_wake_time);
-- 
2.34.1