drm/i915/adlp: Fix register corruption after DDI clock enabling

Accessing the DDI_BUF_CTL register without the port's DDI clock being
enabled (to set/clear the TypeC PHY ownership for the port) can lead to
a corrupted value read during any i915 register access right after the
DDI clock is enabled.

The root cause is the way clock synchronization works for this register,
controlled by the CHICKEN_DCPR_1 DDI_CLOCK_REG_ACCESS flag. Correctly
this flag should be cleared on ADLP (see the Bspec link below), however
after bootup the flag is set.

One easily reproducible issue is an unclaimed register access of the
PWR_WELL_CTL_DDI2 register, programmed right after DDI clock enabling to
enable the port's DDI_IO power well (see the HSDES, VLK links below).
With the correct setting above this problem can't be reproduced.

Bspec: 49189
HSDES: 18019028154
VLK: 28328, 28655

Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Arthur J Runyan <arthur.j.runyan@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Acked-by: Arthur J Runyan <arthur.j.runyan@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220323201749.288566-1-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0ad04132ca8ddee0ad44cc8afd8448878c6381ef..a0dba005e997a461cc5ef9944b009a5bb3defb1d 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5908,6 +5908,7 @@
 #define   ICL_DELAY_PMRSP                      REG_BIT(22)
 #define   DISABLE_FLR_SRC                      REG_BIT(15)
 #define   MASK_WAKEMEM                         REG_BIT(13)
+#define   DDI_CLOCK_REG_ACCESS                 REG_BIT(7)
 
 #define GEN11_CHICKEN_DCPR_2                   _MMIO(0x46434)
 #define   DCPR_MASK_MAXLATENCY_MEMUP_CLR       REG_BIT(27)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 8824f269e5f5411a53f0e3ac573fc2afff68c78c..594ab59e4991a6e001f7d4f2fc22500e556b0688 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -7470,6 +7470,9 @@ static void adlp_init_clock_gating(struct drm_i915_private *dev_priv)
 
        /* Wa_22011091694:adlp */
        intel_de_rmw(dev_priv, GEN9_CLKGATE_DIS_5, 0, DPCE_GATING_DIS);
+
+       /* Bspec/49189 Initialize Sequence */
+       intel_de_rmw(dev_priv, GEN8_CHICKEN_DCPR_1, DDI_CLOCK_REG_ACCESS, 0);
 }
 
 static void dg1_init_clock_gating(struct drm_i915_private *dev_priv)