[PATCH V2 2/4] ARM: OMAP3+: PM: VP: move check of idle to separate function

[nm@ti.com (Nishanth Menon)]

In general, the idle check tends to be time sensitive so that the
followon operation after the idle status verification is done in
a timely manner. However, since we'd be using this in multiple
places in follow-on patches, isolate this out to a separate inline
function.

As part of this change, convert the pr_warning to a rate limited
warning as the situation is most probably going to stick around
(since Voltage Processor state machine might be stuck) + a WARN_ONCE
to ensure adequate attention is received. Document the information
about idle timeout. Based on the idea from Kevin Hilman.

Cc: Tony Lindgren <tony@atomide.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
---
 arch/arm/mach-omap2/vp.c |   55 ++++++++++++++++++++++++++++++++++++----------
 arch/arm/mach-omap2/vp.h |    6 ++++-
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/arch/arm/mach-omap2/vp.c b/arch/arm/mach-omap2/vp.c
index faefef7..4723879 100644
--- a/arch/arm/mach-omap2/vp.c
+++ b/arch/arm/mach-omap2/vp.c
@@ -1,5 +1,6 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/ratelimit.h>
 
 #include "common.h"
 
@@ -9,6 +10,45 @@
 #include "prm-regbits-44xx.h"
 #include "prm44xx.h"
 
+/**
+ * _vp_wait_for_idle() - wait for voltage processor to idle
+ * @voltdm:	voltage domain
+ * @vp:		voltage processor instance
+ *
+ * In some conditions, it is important to ensure that Voltage Processor
+ * is idle before performing operations on the Voltage Processor(VP).
+ * This is primarily to ensure that VP state machine does not enter into
+ * invalid state.
+ *
+ * Returns -ETIMEDOUT if timeout occurs - This could be critical failure
+ * as it indicates that Voltage processor might have it's state machine
+ * stuck up without recovering out(theoretically should never happen
+ * ofcourse). Returns 0 if idle state is detected.
+ *
+ * Note: callers are expected to ensure requisite checks are performed
+ * on the pointers passed.
+ */
+static inline int _vp_wait_for_idle(struct voltagedomain *voltdm,
+				    struct omap_vp_instance *vp)
+{
+	int timeout;
+
+	omap_test_timeout((voltdm->read(vp->vstatus) &
+			   vp->common->vstatus_vpidle), VP_IDLE_TIMEOUT,
+			  timeout);
+
+	if (timeout >= VP_IDLE_TIMEOUT) {
+		/* Dont spam the console but ensure we catch attention */
+		pr_warn_ratelimited("%s: vdd_%s idle timedout\n",
+				    __func__, voltdm->name);
+		WARN_ONCE("vdd_%s idle timedout\n", voltdm->name);
+
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
 static u32 _vp_set_init_voltage(struct voltagedomain *voltdm, u32 volt)
 {
 	struct omap_vp_instance *vp = voltdm->vp;
@@ -241,7 +281,6 @@ void omap_vp_disable(struct voltagedomain *voltdm)
 {
 	struct omap_vp_instance *vp;
 	u32 vpconfig;
-	int timeout;
 
 	if (!voltdm || IS_ERR(voltdm)) {
 		pr_warning("%s: VDD specified does not exist!\n", __func__);
@@ -267,16 +306,10 @@ void omap_vp_disable(struct voltagedomain *voltdm)
 	vpconfig &= ~vp->common->vpconfig_vpenable;
 	voltdm->write(vpconfig, vp->vpconfig);
 
-	/*
-	 * Wait for VP idle Typical latency is <2us. Maximum latency is ~100us
-	 */
-	omap_test_timeout((voltdm->read(vp->vstatus) &
-			   vp->common->vstatus_vpidle), VP_IDLE_TIMEOUT,
-			  timeout);
-
-	if (timeout >= VP_IDLE_TIMEOUT)
-		pr_warning("%s: vdd_%s idle timedout\n",
-			__func__, voltdm->name);
+	if (_vp_wait_for_idle(voltdm, vp)) {
+		pr_warn_ratelimited("%s: vdd_%s timedout after disable!!\n",
+				    __func__, voltdm->name);
+	}
 
 	vp->enabled = false;
 
diff --git a/arch/arm/mach-omap2/vp.h b/arch/arm/mach-omap2/vp.h
index ac1d6cf..4655b39 100644
--- a/arch/arm/mach-omap2/vp.h
+++ b/arch/arm/mach-omap2/vp.h
@@ -30,7 +30,11 @@ struct voltagedomain;
 #define OMAP4_VP_VDD_IVA_ID 1
 #define OMAP4_VP_VDD_MPU_ID 2
 
-/* XXX document */
+/*
+ * Time out for Voltage processor in micro seconds. Typical latency is < 2uS,
+ * but worst case latencies could be around 3-200uS depending on where we
+ * interrupted VP's operation.
+ */
 #define VP_IDLE_TIMEOUT		200
 #define VP_TRANXDONE_TIMEOUT	300
 
-- 
1.7.9.5