drm/i915: BXT DDI PHY sequence BUN

According to the BSpec update, bit 7 of PORT_CL1CM_DW0 register needs to be
checked to ensure that the register is in accessible state.
Also, based on a BSpec update, changing the timeout value to
check iphypwrgood, from 10ms to wait for up to 100us.

v2: [Ville] use wait_for_us instead of the atomic call.
v3: [Jani/Imre] read register only once

Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Reported-by: Philippe Lecluse <Philippe.Lecluse@intel.com>
Cc: Deak, Imre <imre.deak@intel.com>
Cc: Nikula, Jani <jani.nikula@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459446354-19012-1-git-send-email-vandana.kannan@intel.com

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index c839ce9..6df3c59 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1324,6 +1324,7 @@ enum skl_disp_power_wells {
 #define _PORT_CL1CM_DW0_A              0x162000
 #define _PORT_CL1CM_DW0_BC             0x6C000
 #define   PHY_POWER_GOOD               (1 << 16)
+#define   PHY_RESERVED                 (1 << 7)
 #define BXT_PORT_CL1CM_DW0(phy)                _BXT_PHY((phy), _PORT_CL1CM_DW0_BC, \
                                                        _PORT_CL1CM_DW0_A)
 

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 1e08385..3d62b60 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1732,9 +1732,18 @@ static void broxton_phy_init(struct drm_i915_private *dev_priv,
        val |= GT_DISPLAY_POWER_ON(phy);
        I915_WRITE(BXT_P_CR_GT_DISP_PWRON, val);
 
-       /* Considering 10ms timeout until BSpec is updated */
-       if (wait_for(I915_READ(BXT_PORT_CL1CM_DW0(phy)) & PHY_POWER_GOOD, 10))
+       /*
+        * The PHY registers start out inaccessible and respond to reads with
+        * all 1s.  Eventually they become accessible as they power up, then
+        * the reserved bit will give the default 0.  Poll on the reserved bit
+        * becoming 0 to find when the PHY is accessible.
+        * HW team confirmed that the time to reach phypowergood status is
+        * anywhere between 50 us and 100us.
+        */
+       if (wait_for_us(((I915_READ(BXT_PORT_CL1CM_DW0(phy)) &
+               (PHY_RESERVED | PHY_POWER_GOOD)) == PHY_POWER_GOOD), 100)) {
                DRM_ERROR("timeout during PHY%d power on\n", phy);
+       }
 
        for (port =  (phy == DPIO_PHY0 ? PORT_B : PORT_A);
             port <= (phy == DPIO_PHY0 ? PORT_C : PORT_A); port++) {