ARM: tegra: emc: add reference counting to early ack disablement

Bug 995950

Signed-off-by: Sang-Hun Lee <sanlee@nvidia.com>
Reviewed-on: http://git-master/r/110190
(cherry picked from commit cbfc31fb126cd651157125d1785135eced6587dd)

Change-Id: I44eb889235db82b0efda238b87be5612425afb9d
Reviewed-on: http://git-master/r/110978
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>

3 files changed, 45 insertions, 9 deletions

diff --git a/arch/arm/mach-tegra/include/mach/clk.h b/arch/arm/mach-tegra/include/mach/clk.h
index 0fbbf24d5959..01d322a448d1 100644
--- a/arch/arm/mach-tegra/include/mach/clk.h
+++ b/arch/arm/mach-tegra/include/mach/clk.h
@@ -6,7 +6,7 @@
  * Author:
  *	Erik Gilling <konkers@google.com>
  *
- * Copyright (C) 2010-2011 NVIDIA Corporation
+ * Copyright (C) 2010-2012 NVIDIA Corporation
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
@@ -47,10 +47,20 @@ static inline int tegra_dvfs_set_rate(struct clk *c, unsigned long rate)
 unsigned long clk_get_rate_all_locked(struct clk *c);
 #ifdef CONFIG_ARCH_TEGRA_2x_SOC
 void tegra_sdmmc_tap_delay(struct clk *c, int delay);
+
+static inline int tegra_emc_enable_eack(void) {
+	return 0;
+}
+
+static inline int tegra_emc_disable_eack(void) {
+	return 0;
+}
 #else
 static inline void tegra_sdmmc_tap_delay(struct clk *c, int delay)
 {
 }
+int tegra_emc_enable_eack(void);
+int tegra_emc_disable_eack(void);
 #endif
 int tegra_dvfs_rail_disable_by_name(const char *reg_id);
 int tegra_clk_cfg_ex(struct clk *c, enum tegra_clk_ex_param p, u32 setting);
diff --git a/arch/arm/mach-tegra/tegra3_emc.c b/arch/arm/mach-tegra/tegra3_emc.c
index a70f6aca8c3f..6d430b0a99e3 100644
--- a/arch/arm/mach-tegra/tegra3_emc.c
+++ b/arch/arm/mach-tegra/tegra3_emc.c
@@ -1,7 +1,7 @@
 /*
  * arch/arm/mach-tegra/tegra3_emc.c
  *
- * Copyright (C) 2011 NVIDIA Corporation
+ * Copyright (C) 2012 NVIDIA Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -1172,24 +1172,51 @@ int tegra_emc_set_over_temp_state(unsigned long state)
 	return 0;
 }
 
-int tegra_emc_set_eack_state(unsigned long state)
+/* non-zero state value will reduce eack_disable_refcnt */
+static int tegra_emc_set_eack_state(unsigned long state)
 {
 	unsigned long flags;
 	u32 mc_override;
+	static int eack_disable_refcnt = 0;
 
 	spin_lock_irqsave(&emc_access_lock, flags);
 
-	mc_override = mc_readl(MC_EMEM_ARB_OVERRIDE);
-
-	if (state)
+	/*
+	 * refcnt > 0 implies there is at least one client requiring eack
+	 * disabled. refcnt of 0 implies eack is enabled
+	 */
+	if (eack_disable_refcnt == 1 && state) {
+		mc_override = mc_readl(MC_EMEM_ARB_OVERRIDE);
 		enable_early_ack(mc_override);
-	else
+	} else if (eack_disable_refcnt == 0 && !state) {
+		mc_override = mc_readl(MC_EMEM_ARB_OVERRIDE);
 		disable_early_ack(mc_override);
+	}
+
+	if (state) {
+		if (likely(eack_disable_refcnt > 0)) {
+			--eack_disable_refcnt;
+		} else {
+			pr_err("%s: Ignored a request to underflow eack "
+				"disable reference counter\n",__func__);
+			dump_stack();
+		}
+	} else {
+		++eack_disable_refcnt;
+	}
 
 	spin_unlock_irqrestore(&emc_access_lock, flags);
 	return 0;
 }
 
+int tegra_emc_enable_eack(void) {
+	return tegra_emc_set_eack_state(1);
+}
+
+int tegra_emc_disable_eack(void) {
+	return tegra_emc_set_eack_state(0);
+}
+
 #ifdef CONFIG_DEBUG_FS
 
 static struct dentry *emc_debugfs_root;
diff --git a/arch/arm/mach-tegra/tegra3_emc.h b/arch/arm/mach-tegra/tegra3_emc.h
index 185d77762da2..f59654295ba4 100644
--- a/arch/arm/mach-tegra/tegra3_emc.h
+++ b/arch/arm/mach-tegra/tegra3_emc.h
@@ -1,7 +1,7 @@
 /*
  * arch/arm/mach-tegra/tegra3_emc.h
  *
- * Copyright (C) 2011 NVIDIA Corporation
+ * Copyright (C) 2012 NVIDIA Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -61,7 +61,6 @@ void tegra_emc_dram_type_init(struct clk *c);
 int tegra_emc_get_dram_type(void);
 int tegra_emc_get_dram_temperature(void);
 int tegra_emc_set_over_temp_state(unsigned long state);
-int tegra_emc_set_eack_state(unsigned long state);
 
 #ifdef CONFIG_PM_SLEEP
 void tegra_mc_timing_restore(void);