[PATCH 03/10] drm/i915: fix intel_init_power_wells

[Paulo Zanoni <przanoni@gmail.com>]

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

The current code was wrong in many different ways, so this is a full
rewrite. We don't have "different power wells for different parts of
the GPU", we have a single power well, but we have multiple registers
that can be used to request enabling/disabling the power well. So
let's be a good citizen and only use the register we're supposed to
use, except when we're loading the driver, where we clear the request
made by the BIOS.

If any of the registers is requesting the power well to be enabled, it
will be enabled. If none of the registers is requesting the power well
to be enabled, it will be disabled.

For now we're just forcing the power well to be enabled, but in the
next commits we'll change this.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |    8 ++--
 drivers/gpu/drm/i915/intel_display.c |    5 +--
 drivers/gpu/drm/i915/intel_drv.h     |    2 +-
 drivers/gpu/drm/i915/intel_pm.c      |   70 +++++++++++++++++++++++++---------
 4 files changed, 59 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 2521617..f054554 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4414,10 +4414,10 @@
 #define   AUDIO_CP_READY_C		(1<<9)
 
 /* HSW Power Wells */
-#define HSW_PWR_WELL_CTL1			0x45400 /* BIOS */
-#define HSW_PWR_WELL_CTL2			0x45404 /* Driver */
-#define HSW_PWR_WELL_CTL3			0x45408 /* KVMR */
-#define HSW_PWR_WELL_CTL4			0x4540C /* Debug */
+#define HSW_PWR_WELL_BIOS			0x45400 /* CTL1 */
+#define HSW_PWR_WELL_DRIVER			0x45404 /* CTL2 */
+#define HSW_PWR_WELL_KVMR			0x45408 /* CTL3 */
+#define HSW_PWR_WELL_DEBUG			0x4540C /* CTL4 */
 #define   HSW_PWR_WELL_ENABLE			(1<<31)
 #define   HSW_PWR_WELL_STATE			(1<<30)
 #define HSW_PWR_WELL_CTL5			0x45410
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b35902e..4a9f048 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8647,10 +8647,7 @@ static void i915_disable_vga(struct drm_device *dev)
 
 void intel_modeset_init_hw(struct drm_device *dev)
 {
-	/* We attempt to init the necessary power wells early in the initialization
-	 * time, so the subsystems that expect power to be enabled can work.
-	 */
-	intel_init_power_wells(dev);
+	intel_init_power_well(dev);
 
 	intel_prepare_ddi(dev);
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index aeff0d1..8cfad75 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -666,7 +666,7 @@ extern void intel_update_fbc(struct drm_device *dev);
 extern void intel_gpu_ips_init(struct drm_i915_private *dev_priv);
 extern void intel_gpu_ips_teardown(void);
 
-extern void intel_init_power_wells(struct drm_device *dev);
+extern void intel_init_power_well(struct drm_device *dev);
 extern void intel_enable_gt_powersave(struct drm_device *dev);
 extern void intel_disable_gt_powersave(struct drm_device *dev);
 extern void gen6_gt_check_fifodbg(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 5a8a72c..2273b9c 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4043,33 +4043,69 @@ void intel_init_clock_gating(struct drm_device *dev)
 	dev_priv->display.init_clock_gating(dev);
 }
 
-/* Starting with Haswell, we have different power wells for
- * different parts of the GPU. This attempts to enable them all.
+static void intel_set_power_well(struct drm_device *dev, bool enable)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool is_enabled, enable_requested;
+	uint32_t tmp;
+
+	tmp = I915_READ(HSW_PWR_WELL_DRIVER);
+	is_enabled = !!(tmp & HSW_PWR_WELL_STATE);
+	enable_requested = !!(tmp & HSW_PWR_WELL_ENABLE);
+
+	if (enable) {
+		if (!enable_requested)
+			I915_WRITE(HSW_PWR_WELL_DRIVER, HSW_PWR_WELL_ENABLE);
+
+		if (!is_enabled) {
+			DRM_DEBUG_KMS("Enabling power well\n");
+			if (wait_for((I915_READ(HSW_PWR_WELL_DRIVER) &
+				      HSW_PWR_WELL_STATE), 20))
+				DRM_ERROR("Timeout enabling power well\n");
+		}
+	} else {
+		if (enable_requested)
+			I915_WRITE(HSW_PWR_WELL_DRIVER, 0);
+
+		if (is_enabled) {
+			if (I915_READ(HSW_PWR_WELL_BIOS) & HSW_PWR_WELL_ENABLE)
+				DRM_DEBUG_KMS("Not disabling power well: requested by BIOS\n");
+			else if (I915_READ(HSW_PWR_WELL_KVMR) & HSW_PWR_WELL_ENABLE)
+				DRM_DEBUG_KMS("Not disabling power well: requested by KVMR\n");
+			else if (I915_READ(HSW_PWR_WELL_DEBUG) & HSW_PWR_WELL_ENABLE)
+				DRM_DEBUG_KMS("Not disabling power well: requested by DEBUG\n");
+			else {
+				DRM_DEBUG_KMS("Disabling power well\n");
+				if (wait_for((I915_READ(HSW_PWR_WELL_DRIVER) &
+					      HSW_PWR_WELL_STATE) == 0, 20))
+					DRM_ERROR("Timeout disabling power well\n");
+			}
+		}
+	}
+}
+
+/*
+ * Starting with Haswell, we have a "Power Down Well" that can be turned off
+ * when not needed anymore. We have 4 registers that can request the power well
+ * to be enabled, and it will only be disabled if none of the registers is
+ * requesting it to be enabled.
  */
-void intel_init_power_wells(struct drm_device *dev)
+void intel_init_power_well(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	unsigned long power_wells[] = {
-		HSW_PWR_WELL_CTL1,
-		HSW_PWR_WELL_CTL2,
-		HSW_PWR_WELL_CTL4
-	};
-	int i;
 
 	if (!IS_HASWELL(dev))
 		return;
 
 	mutex_lock(&dev->struct_mutex);
 
-	for (i = 0; i < ARRAY_SIZE(power_wells); i++) {
-		int well = I915_READ(power_wells[i]);
+	/* For now, we need the power well to be always enabled. */
+	intel_set_power_well(dev, true);
 
-		if ((well & HSW_PWR_WELL_STATE) == 0) {
-			I915_WRITE(power_wells[i], well & HSW_PWR_WELL_ENABLE);
-			if (wait_for((I915_READ(power_wells[i]) & HSW_PWR_WELL_STATE), 20))
-				DRM_ERROR("Error enabling power well %lx\n", power_wells[i]);
-		}
-	}
+	/* We're taking over the BIOS, so clear any requests made by it since
+	 * the driver is in charge now. */
+	if (I915_READ(HSW_PWR_WELL_BIOS) & HSW_PWR_WELL_ENABLE)
+		I915_WRITE(HSW_PWR_WELL_BIOS, 0);
 
 	mutex_unlock(&dev->struct_mutex);
 }
-- 
1.7.10.4