[PATCH 2/8] drm/i915/cdclk: Add and use xe2lpd_mdclk_source_sel()

[Gustavo Sousa <gustavo.sousa@intel.com>]

There will be future changes that rely on the source of the MDCLK. Let's
have xe2lpd_mdclk_source_sel() as the function responsible for reporting
that information.

Bspec: 69090
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 17 ++++++++++++++++-
 drivers/gpu/drm/i915/i915_reg.h            |  4 +++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 407bd541eb46..bf84bf27213f 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -1876,6 +1876,21 @@ static bool cdclk_pll_is_unknown(unsigned int vco)
 	return vco == ~0;
 }
 
+static u32 xe2lpd_mdclk_source_sel(struct drm_i915_private *i915)
+{
+	if (DISPLAY_VER(i915) >= 20)
+		return MDCLK_SOURCE_SEL_CDCLK_PLL;
+
+	/*
+	 * Earlier display IPs do not provide means of selecting the
+	 * MDCLK source, but MDCLK_SOURCE_SEL_CD2XCLK is a nice default,
+	 * since it reflects the source used for those and allows
+	 * xe2lpd_mdclk_source_sel() to be used in logic that depends on
+	 * it.
+	 */
+	return MDCLK_SOURCE_SEL_CD2XCLK;
+}
+
 static bool cdclk_compute_crawl_and_squash_midpoint(struct drm_i915_private *i915,
 						    const struct intel_cdclk_config *old_cdclk_config,
 						    const struct intel_cdclk_config *new_cdclk_config,
@@ -1980,7 +1995,7 @@ static u32 bxt_cdclk_ctl(struct drm_i915_private *i915,
 		val |= BXT_CDCLK_SSA_PRECHARGE_ENABLE;
 
 	if (DISPLAY_VER(i915) >= 20)
-		val |= MDCLK_SOURCE_SEL_CDCLK_PLL;
+		val |= xe2lpd_mdclk_source_sel(i915);
 	else
 		val |= skl_cdclk_decimal(cdclk);
 
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index e00557e1a57f..eb953ed1f113 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5900,7 +5900,9 @@ enum skl_power_gate {
 #define  CDCLK_FREQ_540		REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 1)
 #define  CDCLK_FREQ_337_308		REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 2)
 #define  CDCLK_FREQ_675_617		REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 3)
-#define  MDCLK_SOURCE_SEL_CDCLK_PLL	REG_BIT(25)
+#define  MDCLK_SOURCE_SEL_MASK		REG_GENMASK(25, 25)
+#define  MDCLK_SOURCE_SEL_CD2XCLK	REG_FIELD_PREP(MDCLK_SOURCE_SEL_MASK, 0)
+#define  MDCLK_SOURCE_SEL_CDCLK_PLL	REG_FIELD_PREP(MDCLK_SOURCE_SEL_MASK, 1)
 #define  BXT_CDCLK_CD2X_DIV_SEL_MASK	REG_GENMASK(23, 22)
 #define  BXT_CDCLK_CD2X_DIV_SEL_1	REG_FIELD_PREP(BXT_CDCLK_CD2X_DIV_SEL_MASK, 0)
 #define  BXT_CDCLK_CD2X_DIV_SEL_1_5	REG_FIELD_PREP(BXT_CDCLK_CD2X_DIV_SEL_MASK, 1)
-- 
2.44.0