[PATCH] Check for a min level when computing the watermark.

[Thomas Richter <richter@rus.uni-stuttgart.de>]

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Dear intel experts,

the attached patch is a minimally invasive modification of the watermark 
computation for the 830GM chipset graphics. It adds a minimum watermark 
level to test against. The minimum value is zero for all other families 
of the intel chipset graphics, thus causing no change there.

What is still strange is that the default watermark level is only used 
if the watermark level computation returns a value below zero, though 
values *below* the default value are acceptable as long as the are above 
or equal to zero. Anyhow, I keep it like this for the time being to 
avoid breaking anything.

Greetings,
	Thomas


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>From 4ff44b36c3ca8ac0255700aaa8999e75efbf9598 Mon Sep 17 00:00:00 2001
From: thor <thor@math.tu-berlin.de>
Date: Sat, 7 Jun 2014 22:23:16 +0200
Subject: [PATCH] Added a min watermark level.

Signed-off-by: thor <thor@math.tu-berlin.de>
---
 drivers/gpu/drm/i915/i915_reg.h  |    1 +
 drivers/gpu/drm/i915/intel_drv.h |    1 +
 drivers/gpu/drm/i915/intel_pm.c  |   16 ++++++++++++++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 286f05c..442240b 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3897,6 +3897,7 @@ enum punit_power_well {
 #define I915_FIFO_SIZE		95
 #define I855GM_FIFO_SIZE	127 /* In cachelines */
 #define I830_FIFO_SIZE		95
+#define I830_MIN_WM		8
 
 #define VALLEYVIEW_MAX_WM	0xff
 #define G4X_MAX_WM		0x3f
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 78d4124..16d2f68 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -458,6 +458,7 @@ struct intel_plane {
 
 struct intel_watermark_params {
 	unsigned long fifo_size;
+	unsigned long min_wm;
 	unsigned long max_wm;
 	unsigned long default_wm;
 	unsigned long guard_size;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index f83d1ff..ac8a832 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -866,6 +866,7 @@ static int i845_get_fifo_size(struct drm_device *dev, int plane)
 /* Pineview has different values for various configs */
 static const struct intel_watermark_params pineview_display_wm = {
 	.fifo_size = PINEVIEW_DISPLAY_FIFO,
+	.min_wm = 0,
 	.max_wm = PINEVIEW_MAX_WM,
 	.default_wm = PINEVIEW_DFT_WM,
 	.guard_size = PINEVIEW_GUARD_WM,
@@ -873,6 +874,7 @@ static const struct intel_watermark_params pineview_display_wm = {
 };
 static const struct intel_watermark_params pineview_display_hplloff_wm = {
 	.fifo_size = PINEVIEW_DISPLAY_FIFO,
+	.min_wm = 0,
 	.max_wm = PINEVIEW_MAX_WM,
 	.default_wm = PINEVIEW_DFT_HPLLOFF_WM,
 	.guard_size = PINEVIEW_GUARD_WM,
@@ -880,6 +882,7 @@ static const struct intel_watermark_params pineview_display_hplloff_wm = {
 };
 static const struct intel_watermark_params pineview_cursor_wm = {
 	.fifo_size = PINEVIEW_CURSOR_FIFO,
+	.min_wm = 0,
 	.max_wm = PINEVIEW_CURSOR_MAX_WM,
 	.default_wm = PINEVIEW_CURSOR_DFT_WM,
 	.guard_size = PINEVIEW_CURSOR_GUARD_WM,
@@ -887,6 +890,7 @@ static const struct intel_watermark_params pineview_cursor_wm = {
 };
 static const struct intel_watermark_params pineview_cursor_hplloff_wm = {
 	.fifo_size = PINEVIEW_CURSOR_FIFO,
+	.min_wm = 0,
 	.max_wm = PINEVIEW_CURSOR_MAX_WM,
 	.default_wm = PINEVIEW_CURSOR_DFT_WM,
 	.guard_size = PINEVIEW_CURSOR_GUARD_WM,
@@ -894,6 +898,7 @@ static const struct intel_watermark_params pineview_cursor_hplloff_wm = {
 };
 static const struct intel_watermark_params g4x_wm_info = {
 	.fifo_size = G4X_FIFO_SIZE,
+	.min_wm = 0,
 	.max_wm = G4X_MAX_WM,
 	.default_wm = G4X_MAX_WM,
 	.guard_size = 2,
@@ -901,6 +906,7 @@ static const struct intel_watermark_params g4x_wm_info = {
 };
 static const struct intel_watermark_params g4x_cursor_wm_info = {
 	.fifo_size = I965_CURSOR_FIFO,
+	.min_wm = 0,
 	.max_wm = I965_CURSOR_MAX_WM,
 	.default_wm = I965_CURSOR_DFT_WM,
 	.guard_size = 2,
@@ -908,6 +914,7 @@ static const struct intel_watermark_params g4x_cursor_wm_info = {
 };
 static const struct intel_watermark_params valleyview_wm_info = {
 	.fifo_size = VALLEYVIEW_FIFO_SIZE,
+	.min_wm = 0,
 	.max_wm = VALLEYVIEW_MAX_WM,
 	.default_wm = VALLEYVIEW_MAX_WM,
 	.guard_size = 2,
@@ -915,6 +922,7 @@ static const struct intel_watermark_params valleyview_wm_info = {
 };
 static const struct intel_watermark_params valleyview_cursor_wm_info = {
 	.fifo_size = I965_CURSOR_FIFO,
+	.min_wm = 0,
 	.max_wm = VALLEYVIEW_CURSOR_MAX_WM,
 	.default_wm = I965_CURSOR_DFT_WM,
 	.guard_size = 2,
@@ -922,6 +930,7 @@ static const struct intel_watermark_params valleyview_cursor_wm_info = {
 };
 static const struct intel_watermark_params i965_cursor_wm_info = {
 	.fifo_size = I965_CURSOR_FIFO,
+	.min_wm = 0,
 	.max_wm = I965_CURSOR_MAX_WM,
 	.default_wm = I965_CURSOR_DFT_WM,
 	.guard_size = 2,
@@ -929,6 +938,7 @@ static const struct intel_watermark_params i965_cursor_wm_info = {
 };
 static const struct intel_watermark_params i945_wm_info = {
 	.fifo_size = I945_FIFO_SIZE,
+	.min_wm = 0,
 	.max_wm = I915_MAX_WM,
 	.default_wm = 1,
 	.guard_size = 2,
@@ -936,6 +946,7 @@ static const struct intel_watermark_params i945_wm_info = {
 };
 static const struct intel_watermark_params i915_wm_info = {
 	.fifo_size = I915_FIFO_SIZE,
+	.min_wm = 0,
 	.max_wm = I915_MAX_WM,
 	.default_wm = 1,
 	.guard_size = 2,
@@ -943,6 +954,7 @@ static const struct intel_watermark_params i915_wm_info = {
 };
 static const struct intel_watermark_params i830_wm_info = {
 	.fifo_size = I855GM_FIFO_SIZE,
+	.min_wm = I830_MIN_WM,
 	.max_wm = I915_MAX_WM,
 	.default_wm = 1,
 	.guard_size = 2,
@@ -950,6 +962,7 @@ static const struct intel_watermark_params i830_wm_info = {
 };
 static const struct intel_watermark_params i845_wm_info = {
 	.fifo_size = I830_FIFO_SIZE,
+	.min_wm = I830_MIN_WM,
 	.max_wm = I915_MAX_WM,
 	.default_wm = 1,
 	.guard_size = 2,
@@ -1003,6 +1016,9 @@ static unsigned long intel_calculate_wm(unsigned long clock_in_khz,
 		wm_size = wm->max_wm;
 	if (wm_size <= 0)
 		wm_size = wm->default_wm;
+	if (wm_size < (long)wm->min_wm)
+		wm_size = wm->min_wm;
+
 	return wm_size;
 }
 
-- 
1.7.10.4


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