[PATCH 2/3] drm/i915/dsi: Don't set/read the DSI C clock divider on GLK

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

GLK doesn't use the DSI C clock at all, no need to program
the divider for it. Bspec even says: "Do not program this field".

However looks like some firmware versions program this and
some do not. In order to avoid bogus fastset mismatches
we should also filter it out during readout.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/vlv_dsi_pll.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/vlv_dsi_pll.c b/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
index 2ed47e7d1051..0c88924bc2cd 100644
--- a/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
+++ b/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
@@ -356,6 +356,8 @@ u32 bxt_dsi_get_pclk(struct intel_encoder *encoder,
 	u32 pclk;
 
 	config->dsi_pll.ctrl = intel_de_read(dev_priv, BXT_DSI_PLL_CTL);
+	if (IS_GEMINILAKE(dev_priv))
+		config->dsi_pll.ctrl &= ~BXT_DSIC_16X_BY2;
 
 	pclk = bxt_dsi_pclk(encoder, config);
 
@@ -514,7 +516,9 @@ int bxt_dsi_pll_compute(struct intel_encoder *encoder,
 	 * Spec says both have to be programmed, even if one is not getting
 	 * used. Configure MIPI_CLOCK_CTL dividers in modeset
 	 */
-	config->dsi_pll.ctrl = dsi_ratio | BXT_DSIA_16X_BY2 | BXT_DSIC_16X_BY2;
+	config->dsi_pll.ctrl = dsi_ratio | BXT_DSIA_16X_BY2;
+	if (!IS_GEMINILAKE(dev_priv))
+		config->dsi_pll.ctrl |= BXT_DSIC_16X_BY2;
 
 	/* As per recommendation from hardware team,
 	 * Prog PVD ratio =1 if dsi ratio <= 50
-- 
2.45.3