[PATCH] powerpc: reorg RTAS delay code

This patch attempts to handle RTAS "busy" return codes in a more simple
and consistent manner.  Typical callers of RTAS shouldn't have to
manage wait times and delay calls.

This patch also changes the kernel to use msleep() rather than udelay()
when a runtime delay is necessary.  This will avoid CPU soft lockups
for extended delay conditions.

Signed-off-by: John Rose <johnrose@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 35 insertions, 50 deletions

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 0112318..13496f3 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -370,24 +370,36 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
 	return ret;
 }
 
-/* Given an RTAS status code of 990n compute the hinted delay of 10^n
- * (last digit) milliseconds.  For now we bound at n=5 (100 sec).
+/* For RTAS_BUSY (-2), delay for 1 millisecond.  For an extended busy status
+ * code of 990n, perform the hinted delay of 10^n (last digit) milliseconds.
  */
-unsigned int rtas_extended_busy_delay_time(int status)
+unsigned int rtas_busy_delay_time(int status)
 {
-	int order = status - 9900;
-	unsigned long ms;
+	int order;
+	unsigned int ms = 0;
+
+	if (status == RTAS_BUSY) {
+		ms = 1;
+	} else if (status >= 9900 && status <= 9905) {
+		order = status - 9900;
+		for (ms = 1; order > 0; order--)
+			ms *= 10;
+	}
 
-	if (order < 0)
-		order = 0;	/* RTC depends on this for -2 clock busy */
-	else if (order > 5)
-		order = 5;	/* bound */
+	return ms;
+}
 
-	/* Use microseconds for reasonable accuracy */
-	for (ms = 1; order > 0; order--)
-		ms *= 10;
+/* For an RTAS busy status code, perform the hinted delay. */
+unsigned int rtas_busy_delay(int status)
+{
+	unsigned int ms;
 
-	return ms; 
+	might_sleep();
+	ms = rtas_busy_delay_time(status);
+	if (ms)
+		msleep(ms);
+
+	return ms;
 }
 
 int rtas_error_rc(int rtas_rc)
@@ -438,22 +450,14 @@ int rtas_get_power_level(int powerdomain, int *level)
 int rtas_set_power_level(int powerdomain, int level, int *setlevel)
 {
 	int token = rtas_token("set-power-level");
-	unsigned int wait_time;
 	int rc;
 
 	if (token == RTAS_UNKNOWN_SERVICE)
 		return -ENOENT;
 
-	while (1) {
+	do {
 		rc = rtas_call(token, 2, 2, setlevel, powerdomain, level);
-		if (rc == RTAS_BUSY)
-			udelay(1);
-		else if (rtas_is_extended_busy(rc)) {
-			wait_time = rtas_extended_busy_delay_time(rc);
-			udelay(wait_time * 1000);
-		} else
-			break;
-	}
+	} while (rtas_busy_delay(rc));
 
 	if (rc < 0)
 		return rtas_error_rc(rc);
@@ -463,22 +467,14 @@ int rtas_set_power_level(int powerdomain, int level, int *setlevel)
 int rtas_get_sensor(int sensor, int index, int *state)
 {
 	int token = rtas_token("get-sensor-state");
-	unsigned int wait_time;
 	int rc;
 
 	if (token == RTAS_UNKNOWN_SERVICE)
 		return -ENOENT;
 
-	while (1) {
+	do {
 		rc = rtas_call(token, 2, 2, state, sensor, index);
-		if (rc == RTAS_BUSY)
-			udelay(1);
-		else if (rtas_is_extended_busy(rc)) {
-			wait_time = rtas_extended_busy_delay_time(rc);
-			udelay(wait_time * 1000);
-		} else
-			break;
-	}
+	} while (rtas_busy_delay(rc));
 
 	if (rc < 0)
 		return rtas_error_rc(rc);
@@ -488,23 +484,14 @@ int rtas_get_sensor(int sensor, int index, int *state)
 int rtas_set_indicator(int indicator, int index, int new_value)
 {
 	int token = rtas_token("set-indicator");
-	unsigned int wait_time;
 	int rc;
 
 	if (token == RTAS_UNKNOWN_SERVICE)
 		return -ENOENT;
 
-	while (1) {
+	do {
 		rc = rtas_call(token, 3, 1, NULL, indicator, index, new_value);
-		if (rc == RTAS_BUSY)
-			udelay(1);
-		else if (rtas_is_extended_busy(rc)) {
-			wait_time = rtas_extended_busy_delay_time(rc);
-			udelay(wait_time * 1000);
-		}
-		else
-			break;
-	}
+	} while (rtas_busy_delay(rc));
 
 	if (rc < 0)
 		return rtas_error_rc(rc);
@@ -555,13 +542,11 @@ void rtas_os_term(char *str)
 	do {
 		status = rtas_call(rtas_token("ibm,os-term"), 1, 1, NULL,
 				   __pa(rtas_os_term_buf));
+	} while (rtas_busy_delay(status));
 
-		if (status == RTAS_BUSY)
-			udelay(1);
-		else if (status != 0)
-			printk(KERN_EMERG "ibm,os-term call failed %d\n",
+	if (status != 0)
+		printk(KERN_EMERG "ibm,os-term call failed %d\n",
 			       status);
-	} while (status == RTAS_BUSY);
 }
 
 static int ibm_suspend_me_token = RTAS_UNKNOWN_SERVICE;
@@ -789,7 +774,7 @@ EXPORT_SYMBOL(rtas_token);
 EXPORT_SYMBOL(rtas_call);
 EXPORT_SYMBOL(rtas_data_buf);
 EXPORT_SYMBOL(rtas_data_buf_lock);
-EXPORT_SYMBOL(rtas_extended_busy_delay_time);
+EXPORT_SYMBOL(rtas_busy_delay_time);
 EXPORT_SYMBOL(rtas_get_sensor);
 EXPORT_SYMBOL(rtas_get_power_level);
 EXPORT_SYMBOL(rtas_set_power_level);