ARM: imx: clean and consolidate imx5 suspend and idle code

The imx5 idle code that existed in mm-imx5.c is moved to pm-imx5.c.
The imx5_pm_init call is now exported and called during the
MACHINE_START late_init in supported imx5 platforms.

Remove various enabling/disabling of the gpc_dvfs clock and
enable it once during initialization.  This is a very low
power clock that must be enabled during low power operations.

There are only two "suspend_state_t" imx5 low power modes ever
used.  STOP_POWER_OFF for suspend to mem and
WAIT_UNCLOCKED_POWER_OFF for idle and suspend to standby.  The
latter mode only requires 500 nanoseconds of extra hardware
exit time beyond a basic WFI operation (WAIT_CLOCKED mode) so
no other idle mode is necessary.  Given this information, it
is more efficient to keep the registers in the often used
WAIT_UNCLOCKED_POWER_OFF state and only to and from the
STOP_POWER_OFF register state as needed when suspend to
mem is required.

Signed-off-by: Robert Lee <rob.lee@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 41 insertions, 26 deletions

diff --git a/arch/arm/mach-imx/pm-imx5.c b/arch/arm/mach-imx/pm-imx5.c
index e26a9cb05ed..baf93214f89 100644
--- a/arch/arm/mach-imx/pm-imx5.c
+++ b/arch/arm/mach-imx/pm-imx5.c
@@ -13,18 +13,27 @@
 #include <linux/io.h>
 #include <linux/err.h>
 #include <asm/cacheflush.h>
+#include <asm/system_misc.h>
 #include <asm/tlbflush.h>
 #include <mach/common.h>
 #include <mach/hardware.h>
 #include "crm-regs-imx5.h"
 
-static struct clk *gpc_dvfs_clk;
+/*
+ * The WAIT_UNCLOCKED_POWER_OFF state only requires <= 500ns to exit.
+ * This is also the lowest power state possible without affecting
+ * non-cpu parts of the system.  For these reasons, imx5 should default
+ * to always using this state for cpu idling.  The PM_SUSPEND_STANDBY also
+ * uses this state and needs to take no action when registers remain confgiured
+ * for this state.
+ */
+#define IMX5_DEFAULT_CPU_IDLE_STATE WAIT_UNCLOCKED_POWER_OFF
 
 /*
  * set cpu low power mode before WFI instruction. This function is called
  * mx5 because it can be used for mx50, mx51, and mx53.
  */
-void mx5_cpu_lp_set(enum mxc_cpu_pwr_mode mode)
+static void mx5_cpu_lp_set(enum mxc_cpu_pwr_mode mode)
 {
 	u32 plat_lpc, arm_srpgcr, ccm_clpcr;
 	u32 empgc0, empgc1;
@@ -87,11 +96,6 @@ void mx5_cpu_lp_set(enum mxc_cpu_pwr_mode mode)
 	}
 }
 
-static int mx5_suspend_prepare(void)
-{
-	return clk_prepare_enable(gpc_dvfs_clk);
-}
-
 static int mx5_suspend_enter(suspend_state_t state)
 {
 	switch (state) {
@@ -99,7 +103,7 @@ static int mx5_suspend_enter(suspend_state_t state)
 		mx5_cpu_lp_set(STOP_POWER_OFF);
 		break;
 	case PM_SUSPEND_STANDBY:
-		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
+		/* DEFAULT_IDLE_STATE already configured */
 		break;
 	default:
 		return -EINVAL;
@@ -114,12 +118,10 @@ static int mx5_suspend_enter(suspend_state_t state)
 		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
 	}
 	cpu_do_idle();
-	return 0;
-}
 
-static void mx5_suspend_finish(void)
-{
-	clk_disable_unprepare(gpc_dvfs_clk);
+	/* return registers to default idle state */
+	mx5_cpu_lp_set(IMX5_DEFAULT_CPU_IDLE_STATE);
+	return 0;
 }
 
 static int mx5_pm_valid(suspend_state_t state)
@@ -129,25 +131,38 @@ static int mx5_pm_valid(suspend_state_t state)
 
 static const struct platform_suspend_ops mx5_suspend_ops = {
 	.valid = mx5_pm_valid,
-	.prepare = mx5_suspend_prepare,
 	.enter = mx5_suspend_enter,
-	.finish = mx5_suspend_finish,
 };
 
-static int __init mx5_pm_init(void)
+static void imx5_pm_idle(void)
 {
-	if (!cpu_is_mx51() && !cpu_is_mx53())
-		return 0;
+	if (likely(!tzic_enable_wake()))
+		cpu_do_idle();
+}
+
+static int __init imx5_pm_common_init(void)
+{
+	int ret;
+	struct clk *gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
+
+	if (IS_ERR(gpc_dvfs_clk))
+		return PTR_ERR(gpc_dvfs_clk);
 
-	if (gpc_dvfs_clk == NULL)
-		gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
+	ret = clk_prepare_enable(gpc_dvfs_clk);
+	if (ret)
+		return ret;
 
-	if (!IS_ERR(gpc_dvfs_clk)) {
-		if (cpu_is_mx51())
-			suspend_set_ops(&mx5_suspend_ops);
-	} else
-		return -EPERM;
+	arm_pm_idle = imx5_pm_idle;
+
+	/* Set the registers to the default cpu idle state. */
+	mx5_cpu_lp_set(IMX5_DEFAULT_CPU_IDLE_STATE);
 
 	return 0;
 }
-device_initcall(mx5_pm_init);
+
+void __init imx51_pm_init(void)
+{
+	int ret = imx5_pm_common_init();
+	if (!ret)
+		suspend_set_ops(&mx5_suspend_ops);
+}