[PATCH v4] drm/i915/display: WA to Re-initialize dispcnlunitt1 xosc clock

[Mitul Golani]

The dispcnlunit1_cp_xosc_clk should be de-asserted in display off
and only asserted in display on. As part of this workaround, Display
driver shall execute set-reset sequence at the end of the initialize
sequence to ensure clk does not remain active in display OFF.

HSD: 15013987218

--v2:
- Rebase.
--v3:
- Correct HSD number in commit message.
--v4:
- Reformat commit message.
- Use intel_de_rmw instead of intel_de_write

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
Reviewed-by: Nemesa Garg <nemesa.garg at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_power.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index e288a1b21d7e..8d009f488601 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -1704,6 +1704,14 @@ static void icl_display_core_init(struct drm_i915_private *dev_priv,
 	/* Wa_14011503030:xelpd */
 	if (DISPLAY_VER(dev_priv) == 13)
 		intel_de_write(dev_priv, XELPD_DISPLAY_ERR_FATAL_MASK, ~0);
+
+	/* Wa_15013987218 */
+	if (DISPLAY_VER(dev_priv) == 20) {
+		intel_de_rmw(dev_priv, SOUTH_DSPCLK_GATE_D,
+			     PCH_GMBUSUNIT_CLOCK_GATE_DISABLE);
+		intel_de_rmw(dev_priv, SOUTH_DSPCLK_GATE_D,
+			     PCH_GMBUSUNIT_CLOCK_GATE_DISABLE, 0);
+	}
 }
 
 static void icl_display_core_uninit(struct drm_i915_private *dev_priv)
-- 
2.45.2