[Patch] Add minimum watermark level for I830

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

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Dear Daniel, dear intel experts,

please find a minimally-invasive patch to add a minimum watermark level 
to the current watermark logic. This fixes the flickering and video 
overlay crashes on 830M(G) chipsets. Note that this patch does not alter 
the watermark algorithm on any other family of the intel chipsets.

Greetings,
	Thomas

PS: What I do not understand about the current logic is that there is a 
"default watermark" level if the computed watermark is below zero, 
though computed watermarks can well drop below this default. The 
appended patch still allows that to be backwards compatible, though this 
construction sounds pretty weird to me.



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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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