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[linux-oem,1/4] drm/i915/glk, cnl: Implement WaDisableScalarClockGating

Message ID 20180308031727.19274-2-jesse.sung@canonical.com
State New
Headers show
Series [linux-oem,1/4] drm/i915/glk, cnl: Implement WaDisableScalarClockGating | expand

Commit Message

Wen-chien Jesse Sung March 8, 2018, 3:17 a.m. UTC 
From: Imre Deak <imre.deak@intel.com>

BugLink: https://launchpad.net/bugs/1754216

On GLK and CNL enabling a pipe with its pipe scaler enabled will result
in a FIFO underrun. This happens only once after driver loading or
system/runtime resume, more specifically after power well 1 gets
enabled; subsequent modesets seem to be free of underruns. The BSpec
workaround for this is to disable the pipe scaler clock gating for the
duration of modeset. Based on my tests disabling clock gating must be
done before enabling pipe scaling and we can re-enable it after the pipe
is enabled and one vblank has passed.

For consistency I also checked if plane scaling would cause the same
problem, but that doesn't seem to trigger this problem.

The patch is based on an earlier version from Ander.

v2 (Rodrigo):
- Set also CLKGATE_DIS_PSL bits 8 and 9.
- Add also the BSpec workaround ID.

Cc: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100302
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171002075557.32615-1-imre.deak@intel.com
(cherry picked from commit ed69cd40685c949ec9c65701758bbf9e6840240f)
Signed-off-by: Wen-chien Jesse Sung <jesse.sung@canonical.com>
---
 drivers/gpu/drm/i915/i915_reg.h      | 10 ++++++++++
 drivers/gpu/drm/i915/intel_display.c | 26 ++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 669572a03542..91b1e92dbd82 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3625,6 +3625,16 @@  enum {
 #define   PWM2_GATING_DIS		(1 << 14)
 #define   PWM1_GATING_DIS		(1 << 13)
 
+#define _CLKGATE_DIS_PSL_A		0x46520
+#define _CLKGATE_DIS_PSL_B		0x46524
+#define _CLKGATE_DIS_PSL_C		0x46528
+#define   DPF_GATING_DIS		(1 << 10)
+#define   DPF_RAM_GATING_DIS		(1 << 9)
+#define   DPFR_GATING_DIS		(1 << 8)
+
+#define CLKGATE_DIS_PSL(pipe) \
+	_MMIO_PIPE(pipe, _CLKGATE_DIS_PSL_A, _CLKGATE_DIS_PSL_B)
+
 /*
  * Display engine regs
  */
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7f7b961a4313..0368863ec364 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5300,6 +5300,20 @@  static bool hsw_crtc_supports_ips(struct intel_crtc *crtc)
 	return HAS_IPS(to_i915(crtc->base.dev)) && crtc->pipe == PIPE_A;
 }
 
+static void glk_pipe_scaler_clock_gating_wa(struct drm_i915_private *dev_priv,
+					    enum pipe pipe, bool apply)
+{
+	u32 val = I915_READ(CLKGATE_DIS_PSL(pipe));
+	u32 mask = DPF_GATING_DIS | DPF_RAM_GATING_DIS | DPFR_GATING_DIS;
+
+	if (apply)
+		val |= mask;
+	else
+		val &= ~mask;
+
+	I915_WRITE(CLKGATE_DIS_PSL(pipe), val);
+}
+
 static void haswell_crtc_enable(struct intel_crtc_state *pipe_config,
 				struct drm_atomic_state *old_state)
 {
@@ -5310,6 +5324,7 @@  static void haswell_crtc_enable(struct intel_crtc_state *pipe_config,
 	enum transcoder cpu_transcoder = intel_crtc->config->cpu_transcoder;
 	struct intel_atomic_state *old_intel_state =
 		to_intel_atomic_state(old_state);
+	bool psl_clkgate_wa;
 
 	if (WARN_ON(intel_crtc->active))
 		return;
@@ -5364,6 +5379,12 @@  static void haswell_crtc_enable(struct intel_crtc_state *pipe_config,
 	if (!transcoder_is_dsi(cpu_transcoder))
 		intel_ddi_enable_pipe_clock(pipe_config);
 
+	/* Display WA #1180: WaDisableScalarClockGating: glk, cnl */
+	psl_clkgate_wa = (IS_GEMINILAKE(dev_priv) || IS_CANNONLAKE(dev_priv)) &&
+			 intel_crtc->config->pch_pfit.enabled;
+	if (psl_clkgate_wa)
+		glk_pipe_scaler_clock_gating_wa(dev_priv, pipe, true);
+
 	if (INTEL_GEN(dev_priv) >= 9)
 		skylake_pfit_enable(intel_crtc);
 	else
@@ -5397,6 +5418,11 @@  static void haswell_crtc_enable(struct intel_crtc_state *pipe_config,
 
 	intel_encoders_enable(crtc, pipe_config, old_state);
 
+	if (psl_clkgate_wa) {
+		intel_wait_for_vblank(dev_priv, pipe);
+		glk_pipe_scaler_clock_gating_wa(dev_priv, pipe, false);
+	}
+
 	if (intel_crtc->config->has_pch_encoder) {
 		intel_wait_for_vblank(dev_priv, pipe);
 		intel_wait_for_vblank(dev_priv, pipe);