drm/i915/cdclk: Implement Wa_13012396614

A new workaround was defined for Xe3_LPD, which requires a tweak on how
we handle MDCLK selection.  Implement it.

Reviewed-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Link: https://patch.msgid.link/20251222-display-wa-13012396614-timing-of-mdclk-source-selection-v1-2-a2f7e9447f7a@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>

3 files changed, 31 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 0aa59d624095..7443e5285942 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -39,6 +39,7 @@
 #include "intel_display_regs.h"
 #include "intel_display_types.h"
 #include "intel_display_utils.h"
+#include "intel_display_wa.h"
 #include "intel_dram.h"
 #include "intel_mchbar_regs.h"
 #include "intel_pci_config.h"
@@ -1858,6 +1859,20 @@ static void bxt_de_pll_enable(struct intel_display *display, int vco)
 
 static void icl_cdclk_pll_disable(struct intel_display *display)
 {
+	/*
+	 * Wa_13012396614:
+	 * Fixes: A sporadic race condition between MDCLK selection and PLL
+	 *        enabling.
+	 * Workaround:
+	 *   Change programming of MDCLK source selection in CDCLK_CTL:
+	 *    - When disabling the CDCLK PLL, first set MDCLK source to be CD2XCLK.
+	 *    - When enabling the CDCLK PLL, update MDCLK source selection only
+	 *      after the PLL is enabled (which is already done as part of the
+	 *      normal flow of _bxt_set_cdclk()).
+	 */
+	if (intel_display_wa(display, 13012396614))
+		intel_de_rmw(display, CDCLK_CTL, MDCLK_SOURCE_SEL_MASK, MDCLK_SOURCE_SEL_CD2XCLK);
+
 	intel_de_rmw(display, BXT_DE_PLL_ENABLE,
 		     BXT_DE_PLL_PLL_ENABLE, 0);
 
@@ -2147,10 +2162,20 @@ static u32 bxt_cdclk_ctl(struct intel_display *display,
 	    cdclk >= 500000)
 		val |= BXT_CDCLK_SSA_PRECHARGE_ENABLE;
 
-	if (DISPLAY_VER(display) >= 20)
-		val |= xe2lpd_mdclk_source_sel(display);
-	else
+	if (DISPLAY_VER(display) >= 20) {
+		/*
+		 * Wa_13012396614 requires selecting CD2XCLK as MDCLK source
+		 * prior to disabling the PLL, which is already handled by
+		 * icl_cdclk_pll_disable().  Here we are just making sure
+		 * we keep the expected value.
+		 */
+		if (intel_display_wa(display, 13012396614) && vco == 0)
+			val |= MDCLK_SOURCE_SEL_CD2XCLK;
+		else
+			val |= xe2lpd_mdclk_source_sel(display);
+	} else {
 		val |= skl_cdclk_decimal(cdclk);
+	}
 
 	return val;
 }
diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.c b/drivers/gpu/drm/i915/display/intel_display_wa.c
index 2b360447e92e..581d943b9bdc 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.c
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.c
@@ -62,6 +62,8 @@ static bool intel_display_needs_wa_16025573575(struct intel_display *display)
 bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa, const char *name)
 {
 	switch (wa) {
+	case INTEL_DISPLAY_WA_13012396614:
+		return DISPLAY_VERx100(display) == 3000;
 	case INTEL_DISPLAY_WA_14011503117:
 		return DISPLAY_VER(display) == 13;
 	case INTEL_DISPLAY_WA_14025769978:
diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.h b/drivers/gpu/drm/i915/display/intel_display_wa.h
index 56b586e38306..40f989f19df1 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.h
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.h
@@ -27,6 +27,7 @@ bool intel_display_needs_wa_16023588340(struct intel_display *display);
  * number.
  */
 enum intel_display_wa {
+	INTEL_DISPLAY_WA_13012396614,
 	INTEL_DISPLAY_WA_14011503117,
 	INTEL_DISPLAY_WA_14025769978,
 	INTEL_DISPLAY_WA_15018326506,