[PATCH v2] drm/i915/cx0: Convert C10 PHY PLL SSC state mismatch WARN to a debug message

[Imre Deak <imre.deak@intel.com>]

On C10 PHY PLLs the SSC is enabled by programming the
XELPDP_PORT_CLOCK_CTL / XELPDP_SSC_ENABLE_PLLB flag and the
PHY_C10_VDR_PLL 4..8 registers:

- If SSC is enabled XELPDP_SSC_ENABLE_PLLB is set and the
  PHY_C10_VDR_PLL registers are programmed to non-zero values.
- If SSC is disabled XELPDP_SSC_ENABLE_PLLB is cleared and the
  PHY_C10_VDR_PLL registers are programmed to zeroed-out values.

The driver's state checker verifies if the above settings are consistent,
i.e. if XELPDP_SSC_ENABLE_PLLB being set corresponds to the
PHY_C10_VDR_PLL registers being zeroed-out or not.

On WCL the BIOS programs non-zero values to the PHY_C10_VDR_PLL 4..8
registers, but does not set the XELPDP_SSC_ENABLE_PLLB flag. This will
trigger the following PLL state check warning during driver loading:

<4>[   44.457809] xe 0000:00:02.0: [drm] PHY B: SSC enabled state (no), doesn't match PLL configuration (SSC-enabled)
<4>[   44.457833] WARNING: CPU: 4 PID: 298 at drivers/gpu/drm/i915/display/intel_cx0_phy.c:2281 intel_cx0pll_readout_hw_state+0x221/0x620 [xe]

It's not clear whether the HW uses the PHY_C10_VDR_PLL 4..8 register
values if the XELPDP_SSC_ENABLE_PLLB flag is cleared, or just ignores
them in this case. Since the driver always programs the register values
according to the above, it still makes sense to verify that the
programming happened correctly.

To avoid the state check WARN during driver loading due to the way BIOS
programs the registers, convert the WARN to a debug message.

While at it clarify the debug message.

v2: Clarify the debug message. (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_cx0_phy.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
index 7bd17723e7abb..f6d69627154e5 100644
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
@@ -2278,11 +2278,13 @@ static void intel_c10pll_readout_hw_state(struct intel_encoder *encoder,
 	pll_state->clock = intel_c10pll_calc_port_clock(encoder, pll_state);
 
 	cx0pll_state->ssc_enabled = readout_ssc_state(encoder, true);
-	drm_WARN(display->drm,
-		 cx0pll_state->ssc_enabled != intel_c10pll_ssc_enabled(pll_state),
-		 "PHY %c: SSC enabled state (%s), doesn't match PLL configuration (%s)\n",
-		 phy_name(phy), str_yes_no(cx0pll_state->ssc_enabled),
-		 intel_c10pll_ssc_enabled(pll_state) ? "SSC-enabled" : "SSC-disabled");
+
+	if (cx0pll_state->ssc_enabled != intel_c10pll_ssc_enabled(pll_state))
+		drm_dbg_kms(display->drm,
+			    "PHY %c: SSC state mismatch: port SSC is %s, PLL SSC is %s\n",
+			    phy_name(phy),
+			    str_enabled_disabled(cx0pll_state->ssc_enabled),
+			    str_enabled_disabled(intel_c10pll_ssc_enabled(pll_state)));
 }
 
 static void intel_c10_pll_program(struct intel_display *display,
-- 
2.49.1