drm/i915: support low power watermarks on Ironlake

This patch actually makes the watermark code even uglier (if that's
possible), but has the advantage of sharing code between SNB and ILK at
least.  Longer term we should refactor the watermark stuff into its own
file and clean it up now that we know how it's supposed to work.

Supporting WM2 on my Vaio reduced power consumption by around 0.5W, so
this patch is definitely worthwhile (though it also needs lots of test
coverage).

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[ickle: pass the watermark structs arounds]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_reg.h

@@ -2345,8 +2345,13 @@
 
 /* Memory latency timer register */
 #define MLTR_ILK		0x11222
+#define  MLTR_WM1_SHIFT		0
+#define  MLTR_WM2_SHIFT		8
 /* the unit of memory self-refresh latency time is 0.5us */
 #define  ILK_SRLT_MASK		0x3f
+#define ILK_LATENCY(shift)	(I915_READ(MLTR_ILK) >> (shift) & ILK_SRLT_MASK)
+#define ILK_READ_WM1_LATENCY()	ILK_LATENCY(MLTR_WM1_SHIFT)
+#define ILK_READ_WM2_LATENCY()	ILK_LATENCY(MLTR_WM2_SHIFT)
 
 /* define the fifo size on Ironlake */
 #define ILK_DISPLAY_FIFO	128

drivers/gpu/drm/i915/intel_display.c

@@ -3456,113 +3456,17 @@ static bool ironlake_compute_wm0(struct drm_device *dev,
 	return true;
 }
 
-static void ironlake_update_wm(struct drm_device *dev,
-			       int planea_clock, int planeb_clock,
-			       int sr_hdisplay, int sr_htotal,
-			       int pixel_size)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	int plane_wm, cursor_wm, enabled;
-	int tmp;
-
-	enabled = 0;
-	if (ironlake_compute_wm0(dev, 0,
-				 &ironlake_display_wm_info,
-				 ILK_LP0_PLANE_LATENCY,
-				 &ironlake_cursor_wm_info,
-				 ILK_LP0_CURSOR_LATENCY,
-				 &plane_wm, &cursor_wm)) {
-		I915_WRITE(WM0_PIPEA_ILK,
-			   (plane_wm << WM0_PIPE_PLANE_SHIFT) | cursor_wm);
-		DRM_DEBUG_KMS("FIFO watermarks For pipe A -"
-			      " plane %d, " "cursor: %d\n",
-			      plane_wm, cursor_wm);
-		enabled++;
-	}
-
-	if (ironlake_compute_wm0(dev, 1,
-				 &ironlake_display_wm_info,
-				 ILK_LP0_PLANE_LATENCY,
-				 &ironlake_cursor_wm_info,
-				 ILK_LP0_CURSOR_LATENCY,
-				 &plane_wm, &cursor_wm)) {
-		I915_WRITE(WM0_PIPEB_ILK,
-			   (plane_wm << WM0_PIPE_PLANE_SHIFT) | cursor_wm);
-		DRM_DEBUG_KMS("FIFO watermarks For pipe B -"
-			      " plane %d, cursor: %d\n",
-			      plane_wm, cursor_wm);
-		enabled++;
-	}
-
-	/*
-	 * Calculate and update the self-refresh watermark only when one
-	 * display plane is used.
-	 */
-	tmp = 0;
-	if (enabled == 1) {
-		unsigned long line_time_us;
-		int small, large, plane_fbc;
-		int sr_clock, entries;
-		int line_count, line_size;
-		/* Read the self-refresh latency. The unit is 0.5us */
-		int ilk_sr_latency = I915_READ(MLTR_ILK) & ILK_SRLT_MASK;
-
-		sr_clock = planea_clock ? planea_clock : planeb_clock;
-		line_time_us = (sr_htotal * 1000) / sr_clock;
-
-		/* Use ns/us then divide to preserve precision */
-		line_count = ((ilk_sr_latency * 500) / line_time_us + 1000)
-			/ 1000;
-		line_size = sr_hdisplay * pixel_size;
-
-		/* Use the minimum of the small and large buffer method for primary */
-		small = ((sr_clock * pixel_size / 1000) * (ilk_sr_latency * 500)) / 1000;
-		large = line_count * line_size;
-
-		entries = DIV_ROUND_UP(min(small, large),
-				       ironlake_display_srwm_info.cacheline_size);
-
-		plane_fbc = entries * 64;
-		plane_fbc = DIV_ROUND_UP(plane_fbc, line_size);
-
-		plane_wm = entries + ironlake_display_srwm_info.guard_size;
-		if (plane_wm > (int)ironlake_display_srwm_info.max_wm)
-			plane_wm = ironlake_display_srwm_info.max_wm;
-
-		/* calculate the self-refresh watermark for display cursor */
-		entries = line_count * pixel_size * 64;
-		entries = DIV_ROUND_UP(entries,
-				       ironlake_cursor_srwm_info.cacheline_size);
-
-		cursor_wm = entries + ironlake_cursor_srwm_info.guard_size;
-		if (cursor_wm > (int)ironlake_cursor_srwm_info.max_wm)
-			cursor_wm = ironlake_cursor_srwm_info.max_wm;
-
-		/* configure watermark and enable self-refresh */
-		tmp = (WM1_LP_SR_EN |
-		       (ilk_sr_latency << WM1_LP_LATENCY_SHIFT) |
-		       (plane_fbc << WM1_LP_FBC_SHIFT) |
-		       (plane_wm << WM1_LP_SR_SHIFT) |
-		       cursor_wm);
-		DRM_DEBUG_KMS("self-refresh watermark: display plane %d, fbc lines %d,"
-			      " cursor %d\n", plane_wm, plane_fbc, cursor_wm);
-	}
-	I915_WRITE(WM1_LP_ILK, tmp);
-	/* XXX setup WM2 and WM3 */
-}
-
 /*
  * Check the wm result.
  *
  * If any calculated watermark values is larger than the maximum value that
  * can be programmed into the associated watermark register, that watermark
  * must be disabled.
- *
- * Also return true if all of those watermark values is 0, which is set by
- * sandybridge_compute_srwm, to indicate the latency is ZERO.
  */
-static bool sandybridge_check_srwm(struct drm_device *dev, int level,
-				   int fbc_wm, int display_wm, int cursor_wm)
+static bool ironlake_check_srwm(struct drm_device *dev, int level,
+				int fbc_wm, int display_wm, int cursor_wm,
+				const struct intel_watermark_params *display,
+				const struct intel_watermark_params *cursor)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
@@ -3571,7 +3475,7 @@ static bool sandybridge_check_srwm(struct drm_device *dev, int level,
 
 	if (fbc_wm > SNB_FBC_MAX_SRWM) {
 		DRM_DEBUG_KMS("fbc watermark(%d) is too large(%d), disabling wm%d+\n",
-				fbc_wm, SNB_FBC_MAX_SRWM, level);
+			      fbc_wm, SNB_FBC_MAX_SRWM, level);
 
 		/* fbc has it's own way to disable FBC WM */
 		I915_WRITE(DISP_ARB_CTL,
@@ -3579,15 +3483,15 @@ static bool sandybridge_check_srwm(struct drm_device *dev, int level,
 		return false;
 	}
 
-	if (display_wm > SNB_DISPLAY_MAX_SRWM) {
+	if (display_wm > display->max_wm) {
 		DRM_DEBUG_KMS("display watermark(%d) is too large(%d), disabling wm%d+\n",
-				display_wm, SNB_DISPLAY_MAX_SRWM, level);
+			      display_wm, SNB_DISPLAY_MAX_SRWM, level);
 		return false;
 	}
 
-	if (cursor_wm > SNB_CURSOR_MAX_SRWM) {
+	if (cursor_wm > cursor->max_wm) {
 		DRM_DEBUG_KMS("cursor watermark(%d) is too large(%d), disabling wm%d+\n",
-				cursor_wm, SNB_CURSOR_MAX_SRWM, level);
+			      cursor_wm, SNB_CURSOR_MAX_SRWM, level);
 		return false;
 	}
 
@@ -3602,16 +3506,18 @@ static bool sandybridge_check_srwm(struct drm_device *dev, int level,
 /*
  * Compute watermark values of WM[1-3],
  */
-static bool sandybridge_compute_srwm(struct drm_device *dev, int level,
-				     int hdisplay, int htotal, int pixel_size,
-				     int clock, int latency_ns, int *fbc_wm,
-				     int *display_wm, int *cursor_wm)
+static bool ironlake_compute_srwm(struct drm_device *dev, int level,
+				  int hdisplay, int htotal,
+				  int pixel_size, int clock, int latency_ns,
+				  const struct intel_watermark_params *display,
+				  const struct intel_watermark_params *cursor,
+				  int *fbc_wm, int *display_wm, int *cursor_wm)
 {
 
 	unsigned long line_time_us;
+	int line_count, line_size;
 	int small, large;
 	int entries;
-	int line_count, line_size;
 
 	if (!latency_ns) {
 		*fbc_wm = *display_wm = *cursor_wm = 0;
@@ -3626,24 +3532,110 @@ static bool sandybridge_compute_srwm(struct drm_device *dev, int level,
 	small = ((clock * pixel_size / 1000) * latency_ns) / 1000;
 	large = line_count * line_size;
 
-	entries = DIV_ROUND_UP(min(small, large),
-				sandybridge_display_srwm_info.cacheline_size);
-	*display_wm = entries + sandybridge_display_srwm_info.guard_size;
+	entries = DIV_ROUND_UP(min(small, large), display->cacheline_size);
+	*display_wm = entries + display->guard_size;
 
 	/*
-	 * Spec said:
+	 * Spec says:
 	 * FBC WM = ((Final Primary WM * 64) / number of bytes per line) + 2
 	 */
 	*fbc_wm = DIV_ROUND_UP(*display_wm * 64, line_size) + 2;
 
 	/* calculate the self-refresh watermark for display cursor */
 	entries = line_count * pixel_size * 64;
-	entries = DIV_ROUND_UP(entries,
-			       sandybridge_cursor_srwm_info.cacheline_size);
-	*cursor_wm = entries + sandybridge_cursor_srwm_info.guard_size;
+	entries = DIV_ROUND_UP(entries, cursor->cacheline_size);
+	*cursor_wm = entries + cursor->guard_size;
 
-	return sandybridge_check_srwm(dev, level,
-				      *fbc_wm, *display_wm, *cursor_wm);
+	return ironlake_check_srwm(dev, level,
+				   *fbc_wm, *display_wm, *cursor_wm,
+				   display, cursor);
+}
+
+static void ironlake_update_wm(struct drm_device *dev,
+			       int planea_clock, int planeb_clock,
+			       int hdisplay, int htotal,
+			       int pixel_size)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int fbc_wm, plane_wm, cursor_wm, enabled;
+	int clock;
+
+	enabled = 0;
+	if (ironlake_compute_wm0(dev, 0,
+				 &ironlake_display_wm_info,
+				 ILK_LP0_PLANE_LATENCY,
+				 &ironlake_cursor_wm_info,
+				 ILK_LP0_CURSOR_LATENCY,
+				 &plane_wm, &cursor_wm)) {
+		I915_WRITE(WM0_PIPEA_ILK,
+			   (plane_wm << WM0_PIPE_PLANE_SHIFT) | cursor_wm);
+		DRM_DEBUG_KMS("FIFO watermarks For pipe A -"
+			      " plane %d, " "cursor: %d\n",
+			      plane_wm, cursor_wm);
+		enabled++;
+	}
+
+	if (ironlake_compute_wm0(dev, 1,
+				 &ironlake_display_wm_info,
+				 ILK_LP0_PLANE_LATENCY,
+				 &ironlake_cursor_wm_info,
+				 ILK_LP0_CURSOR_LATENCY,
+				 &plane_wm, &cursor_wm)) {
+		I915_WRITE(WM0_PIPEB_ILK,
+			   (plane_wm << WM0_PIPE_PLANE_SHIFT) | cursor_wm);
+		DRM_DEBUG_KMS("FIFO watermarks For pipe B -"
+			      " plane %d, cursor: %d\n",
+			      plane_wm, cursor_wm);
+		enabled++;
+	}
+
+	/*
+	 * Calculate and update the self-refresh watermark only when one
+	 * display plane is used.
+	 */
+	I915_WRITE(WM3_LP_ILK, 0);
+	I915_WRITE(WM2_LP_ILK, 0);
+	I915_WRITE(WM1_LP_ILK, 0);
+
+	if (enabled != 1)
+		return;
+
+	clock = planea_clock ? planea_clock : planeb_clock;
+
+	/* WM1 */
+	if (!ironlake_compute_srwm(dev, 1, hdisplay, htotal, pixel_size,
+				   clock, ILK_READ_WM1_LATENCY() * 500,
+				   &ironlake_display_srwm_info,
+				   &ironlake_cursor_srwm_info,
+				   &fbc_wm, &plane_wm, &cursor_wm))
+		return;
+
+	I915_WRITE(WM1_LP_ILK,
+		   WM1_LP_SR_EN |
+		   (ILK_READ_WM1_LATENCY() << WM1_LP_LATENCY_SHIFT) |
+		   (fbc_wm << WM1_LP_FBC_SHIFT) |
+		   (plane_wm << WM1_LP_SR_SHIFT) |
+		   cursor_wm);
+
+	/* WM2 */
+	if (!ironlake_compute_srwm(dev, 2, hdisplay, htotal, pixel_size,
+				   clock, ILK_READ_WM2_LATENCY() * 500,
+				   &ironlake_display_srwm_info,
+				   &ironlake_cursor_srwm_info,
+				   &fbc_wm, &plane_wm, &cursor_wm))
+		return;
+
+	I915_WRITE(WM2_LP_ILK,
+		   WM2_LP_EN |
+		   (ILK_READ_WM2_LATENCY() << WM1_LP_LATENCY_SHIFT) |
+		   (fbc_wm << WM1_LP_FBC_SHIFT) |
+		   (plane_wm << WM1_LP_SR_SHIFT) |
+		   cursor_wm);
+
+	/*
+	 * WM3 is unsupported on ILK, probably because we don't have latency
+	 * data for that power state
+	 */
 }
 
 static void sandybridge_update_wm(struct drm_device *dev,
@@ -3701,9 +3693,11 @@ static void sandybridge_update_wm(struct drm_device *dev,
 	clock = planea_clock ? planea_clock : planeb_clock;
 
 	/* WM1 */
-	if (!sandybridge_compute_srwm(dev, 1, hdisplay, htotal, pixel_size,
-				      clock, SNB_READ_WM1_LATENCY() * 500,
-				      &fbc_wm, &plane_wm, &cursor_wm))
+	if (!ironlake_compute_srwm(dev, 1, hdisplay, htotal, pixel_size,
+				   clock, SNB_READ_WM1_LATENCY() * 500,
+				   &sandybridge_display_srwm_info,
+				   &sandybridge_cursor_srwm_info,
+				   &fbc_wm, &plane_wm, &cursor_wm))
 		return;
 
 	I915_WRITE(WM1_LP_ILK,
@@ -3714,10 +3708,12 @@ static void sandybridge_update_wm(struct drm_device *dev,
 		   cursor_wm);
 
 	/* WM2 */
-	if (!sandybridge_compute_srwm(dev, 2,
-				      hdisplay, htotal, pixel_size,
-				      clock, SNB_READ_WM2_LATENCY() * 500,
-				      &fbc_wm, &plane_wm, &cursor_wm))
+	if (!ironlake_compute_srwm(dev, 2,
+				   hdisplay, htotal, pixel_size,
+				   clock, SNB_READ_WM2_LATENCY() * 500,
+				   &sandybridge_display_srwm_info,
+				   &sandybridge_cursor_srwm_info,
+				   &fbc_wm, &plane_wm, &cursor_wm))
 		return;
 
 	I915_WRITE(WM2_LP_ILK,
@@ -3728,10 +3724,12 @@ static void sandybridge_update_wm(struct drm_device *dev,
 		   cursor_wm);
 
 	/* WM3 */
-	if (!sandybridge_compute_srwm(dev, 3,
-				      hdisplay, htotal, pixel_size,
-				      clock, SNB_READ_WM3_LATENCY() * 500,
-				      &fbc_wm, &plane_wm, &cursor_wm))
+	if (!ironlake_compute_srwm(dev, 3,
+				   hdisplay, htotal, pixel_size,
+				   clock, SNB_READ_WM3_LATENCY() * 500,
+				   &sandybridge_display_srwm_info,
+				   &sandybridge_cursor_srwm_info,
+				   &fbc_wm, &plane_wm, &cursor_wm))
 		return;
 
 	I915_WRITE(WM3_LP_ILK,