[PATCH 6/7] drm/i915: add functions to disable and restore LCPLL

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

For now there are no callers, but these functions are going to be
needed for the code that allows Package C8+. Other future features may
also require this code.

v2: - Rebase.
    - Fix D_COMP wait timeout.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |  7 +++
 drivers/gpu/drm/i915/intel_display.c | 92 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h     |  3 ++
 3 files changed, 102 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index bfa6f7f..b57d564 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5007,7 +5007,14 @@
 #define  LCPLL_CLK_FREQ_450		(0<<26)
 #define  LCPLL_CD_CLOCK_DISABLE		(1<<25)
 #define  LCPLL_CD2X_CLOCK_DISABLE	(1<<23)
+#define  LCPLL_POWER_DOWN_ALLOW		(1<<22)
 #define  LCPLL_CD_SOURCE_FCLK		(1<<21)
+#define  LCPLL_CD_SOURCE_FCLK_DONE	(1<<19)
+
+#define D_COMP				(MCHBAR_MIRROR_BASE_SNB + 0x5F0C)
+#define  D_COMP_RCOMP_IN_PROGRESS	(1<<9)
+#define  D_COMP_COMP_FORCE		(1<<8)
+#define  D_COMP_COMP_DISABLE		(1<<0)
 
 /* Pipe WM_LINETIME - watermark line time */
 #define PIPE_WM_LINETIME_A		0x45270
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0741e1f..915da2d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5924,6 +5924,98 @@ static bool ironlake_get_pipe_config(struct intel_crtc *crtc,
 	return true;
 }
 
+/*
+ * This function implements pieces of two sequences from BSpec:
+ * - Sequence for display software to disable LCPLL
+ * - Sequence for display software to allow package C8+
+ * The steps implemented here are just the steps that actually touch the LCPLL
+ * register. Callers should take care of disabling all the display engine
+ * functions, doing the mode unset, fixing interrupts, etc.
+ */
+void hsw_disable_lcpll(struct drm_i915_private *dev_priv,
+		       bool switch_to_fclk, bool allow_power_down)
+{
+	uint32_t val;
+
+	val = I915_READ(LCPLL_CTL);
+
+	if (switch_to_fclk) {
+		val |= LCPLL_CD_SOURCE_FCLK;
+		I915_WRITE(LCPLL_CTL, val);
+		POSTING_READ(LCPLL_CTL);
+
+		udelay(1);
+
+		val = I915_READ(LCPLL_CTL);
+		if (!(val & LCPLL_CD_SOURCE_FCLK_DONE))
+			DRM_ERROR("Switching to FCLK failed\n");
+	}
+
+	val |= LCPLL_PLL_DISABLE;
+	I915_WRITE(LCPLL_CTL, val);
+	POSTING_READ(LCPLL_CTL);
+
+	if (wait_for((I915_READ(LCPLL_CTL) & LCPLL_PLL_LOCK) == 0, 1))
+		DRM_ERROR("LCPLL still locked\n");
+
+	val = I915_READ(D_COMP);
+	val |= D_COMP_COMP_DISABLE;
+	I915_WRITE(D_COMP, val);
+	POSTING_READ(D_COMP);
+
+	if (wait_for((I915_READ(D_COMP) & D_COMP_RCOMP_IN_PROGRESS) == 0, 1))
+		DRM_ERROR("D_COMP RCOMP still in progress\n");
+
+	if (allow_power_down) {
+		val = I915_READ(LCPLL_CTL);
+		val |= LCPLL_POWER_DOWN_ALLOW;
+		I915_WRITE(LCPLL_CTL, val);
+		POSTING_READ(LCPLL_CTL);
+	}
+}
+
+/*
+ * Fully restores LCPLL, disallowing power down and switching back to LCPLL
+ * source.
+ */
+void hsw_restore_lcpll(struct drm_i915_private *dev_priv)
+{
+	uint32_t val;
+
+	val = I915_READ(LCPLL_CTL);
+
+	if (val & LCPLL_POWER_DOWN_ALLOW) {
+		val &= ~LCPLL_POWER_DOWN_ALLOW;
+		I915_WRITE(LCPLL_CTL, val);
+	}
+
+	val = I915_READ(D_COMP);
+	val |= D_COMP_COMP_FORCE;
+	val &= ~D_COMP_COMP_DISABLE;
+	I915_WRITE(D_COMP, val);
+
+	val = I915_READ(LCPLL_CTL);
+	val &= ~LCPLL_PLL_DISABLE;
+	I915_WRITE(LCPLL_CTL, val);
+	POSTING_READ(LCPLL_CTL);
+
+	if (wait_for(I915_READ(LCPLL_CTL) & LCPLL_PLL_LOCK, 5))
+		DRM_ERROR("LCPLL not locked yet\n");
+
+	if (val & LCPLL_CD_SOURCE_FCLK) {
+		val = I915_READ(LCPLL_CTL);
+		val &= ~LCPLL_CD_SOURCE_FCLK;
+		I915_WRITE(LCPLL_CTL, val);
+		POSTING_READ(LCPLL_CTL);
+
+		udelay(1);
+
+		val = I915_READ(LCPLL_CTL);
+		if (val & LCPLL_CD_SOURCE_FCLK_DONE)
+			DRM_ERROR("Switching back to LCPLL failed\n");
+	}
+}
+
 static void haswell_modeset_global_resources(struct drm_device *dev)
 {
 	bool enable = false;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 31087ff..3fbe80b 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -838,5 +838,8 @@ extern bool intel_set_pch_fifo_underrun_reporting(struct drm_device *dev,
 extern void intel_edp_psr_enable(struct intel_dp *intel_dp);
 extern void intel_edp_psr_disable(struct intel_dp *intel_dp);
 extern void intel_edp_psr_update(struct drm_device *dev);
+extern void hsw_disable_lcpll(struct drm_i915_private *dev_priv,
+			      bool switch_to_fclk, bool allow_power_down);
+extern void hsw_restore_lcpll(struct drm_i915_private *dev_priv);
 
 #endif /* __INTEL_DRV_H__ */
-- 
1.8.1.2