drm/i915/vlv: assert and de-assert sideband reset at boot and resume v3

This is a bit like the CMN reset de-assert we do in DPIO_CTL, except
that it resets the whole common lane section of the PHY.  This is
required on machines where the BIOS doesn't do this for us on boot or
resume to properly re-calibrate and get the PHY ready to transmit data.

Without this patch, such machines won't resume correctly much of the time,
with the symptom being a 'port ready' timeout and/or a link training
failure.

Note that simply asserting reset at suspend and de-asserting at resume
is not sufficient, nor is simply de-asserting at boot.  Both of these
cases have been tested and have still been found to have failures on
some configurations.

v2: extract simpler set_power_well function for use in reset_dpio (Imre)
    move to reset_dpio (Daniel & Ville)
v3: don't reset if DPIO reset is already de-asserted (Imre)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 1ce4ad4626e4..bcbd742149c6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1516,6 +1516,25 @@ static void intel_reset_dpio(struct drm_device *dev)
 
         } else {
                 /*
+                 * If DPIO has already been reset, e.g. by BIOS, just skip all
+                 * this.
+                 */
+                if (I915_READ(DPIO_CTL) & DPIO_CMNRST)
+                        return;
+
+                /*
+                 * From VLV2A0_DP_eDP_HDMI_DPIO_driver_vbios_notes_11.docx:
+                 * Need to assert and de-assert PHY SB reset by gating the
+                 * common lane power, then un-gating it.
+                 * Simply ungating isn't enough to reset the PHY enough to get
+                 * ports and lanes running.
+                 */
+                __vlv_set_power_well(dev_priv, PUNIT_POWER_WELL_DPIO_CMN_BC,
+                                     false);
+                __vlv_set_power_well(dev_priv, PUNIT_POWER_WELL_DPIO_CMN_BC,
+                                     true);
+
+                /*
                  * From VLV2A0_DP_eDP_DPIO_driver_vbios_notes_10.docx -
                  *  6.  De-assert cmn_reset/side_reset. Same as VLV X0.
                  *   a. GUnit 0x2110 bit[0] set to 1 (def 0)