drm/i915/display/lspcon: Increase LSPCON mode settle timeout

This is to eliminate all cases of "*ERROR* LSPCON mode hasn't settled",
followed by link training errors. Intel engineers recommended increasing
this timeout and that does resolve the issue.

On some CometLake-based device designs the Parade PS175 takes more than
400ms to settle in PCON mode. 100 reboot trials on one device resulted
in a median settle time of 440ms and a maximum of 444ms. Even after
increasing the timeout to 500ms, 2% of devices still had this error. So
this increases the timeout to 800ms.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9443
Signed-off-by: Pablo Ceballos <pceballos@google.com>
Signed-off-by: Niko Tsirakis <ntsirakis@google.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231002204709.761089-1-ntsirakis@google.com

diff --git a/drivers/gpu/drm/i915/display/intel_lspcon.c b/drivers/gpu/drm/i915/display/intel_lspcon.c
index 152a22a8ffd25804c57f76378058ac882c47b3fe..1d048fa98561bf3a72053a9245410e87cb87a77e 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/display/intel_lspcon.c
@@ -153,6 +153,18 @@ static enum drm_lspcon_mode lspcon_get_current_mode(struct intel_lspcon *lspcon)
        return current_mode;
 }
 
+static int lspcon_get_mode_settle_timeout(struct intel_lspcon *lspcon)
+{
+       /*
+        * On some CometLake-based device designs the Parade PS175 takes more
+        * than 400ms to settle in PCON mode. 100 reboot trials on one device
+        * resulted in a median settle time of 440ms and a maximum of 444ms.
+        * Even after increasing the timeout to 500ms, 2% of devices still had
+        * this error. So this sets the timeout to 800ms.
+        */
+       return lspcon->vendor == LSPCON_VENDOR_PARADE ? 800 : 400;
+}
+
 static enum drm_lspcon_mode lspcon_wait_mode(struct intel_lspcon *lspcon,
                                             enum drm_lspcon_mode mode)
 {
@@ -167,7 +179,8 @@ static enum drm_lspcon_mode lspcon_wait_mode(struct intel_lspcon *lspcon,
        drm_dbg_kms(&i915->drm, "Waiting for LSPCON mode %s to settle\n",
                    lspcon_mode_name(mode));
 
-       wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode, 400);
+       wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode,
+                lspcon_get_mode_settle_timeout(lspcon));
        if (current_mode != mode)
                drm_err(&i915->drm, "LSPCON mode hasn't settled\n");