Subject: [PATCH] reorg RTAS delay code

From: John Rose <[email-masked]>
Date: Fri, 02 Jun 2006 15:30:29 -0500

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 <[email-masked]>

---

This obsoletes the patch in the parent thread, "use msleep for RTAS 
delays".  Sniff tested on POWER5.

Thanks-
John

 2_6_linus-johnrose/arch/powerpc/kernel/rtas-rtc.c   |   30 +++---
 2_6_linus-johnrose/arch/powerpc/kernel/rtas.c       |   86 ++++++++------------
 2_6_linus-johnrose/arch/powerpc/kernel/rtas_flash.c |   25 -----
 2_6_linus-johnrose/include/asm-powerpc/rtas.h       |    8 -
 4 files changed, 57 insertions(+), 92 deletions(-)

diff -puN arch/powerpc/kernel/rtas.c~rtas_delay_reorg arch/powerpc/kernel/rtas.c
--- 2_6_linus/arch/powerpc/kernel/rtas.c~rtas_delay_reorg	2006-06-02 15:09:43.000000000 -0500
+++ 2_6_linus-johnrose/arch/powerpc/kernel/rtas.c	2006-06-02 15:22:37.000000000 -0500
@@ -370,24 +370,35 @@ int rtas_call(int token, int nargs, int 
 	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 (order < 0)
-		order = 0;	/* RTC depends on this for -2 clock busy */
-	else if (order > 5)
-		order = 5;	/* bound */
+	if (status == RTAS_BUSY) {
+		ms = 1;
+	} else if (status >= 9900 && status <= 9905) {
+		order = status - 9900;
+		for (ms = 1; order > 0; order--)
+			ms *= 10;
+	}
+
+	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; 
+	ms = rtas_busy_delay_time(status);
+	if (ms)
+		msleep(ms);
+
+	return ms;
 }
 
 int rtas_error_rc(int rtas_rc)
@@ -438,22 +449,14 @@ int rtas_get_power_level(int powerdomain
 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 +466,14 @@ int rtas_set_power_level(int powerdomain
 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 +483,14 @@ int rtas_get_sensor(int sensor, int inde
 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);
@@ -552,16 +538,14 @@ void rtas_os_term(char *str)
 
 	snprintf(rtas_os_term_buf, 2048, "OS panic: %s", str);
 
-	do {
+	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 +773,7 @@ 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);
diff -puN arch/powerpc/kernel/rtas-rtc.c~rtas_delay_reorg arch/powerpc/kernel/rtas-rtc.c
--- 2_6_linus/arch/powerpc/kernel/rtas-rtc.c~rtas_delay_reorg	2006-06-02 15:09:43.000000000 -0500
+++ 2_6_linus-johnrose/arch/powerpc/kernel/rtas-rtc.c	2006-06-02 15:09:43.000000000 -0500
@@ -14,19 +14,20 @@
 unsigned long __init rtas_get_boot_time(void)
 {
 	int ret[8];
-	int error, wait_time;
+	int error;
+	unsigned int wait_time;
 	u64 max_wait_tb;
 
 	max_wait_tb = get_tb() + tb_ticks_per_usec * 1000 * MAX_RTC_WAIT;
 	do {
 		error = rtas_call(rtas_token("get-time-of-day"), 0, 8, ret);
-		if (error == RTAS_CLOCK_BUSY || rtas_is_extended_busy(error)) {
-			wait_time = rtas_extended_busy_delay_time(error);
+
+		wait_time = rtas_busy_delay_time(error);
+		if (wait_time) {
 			/* This is boot time so we spin. */
 			udelay(wait_time*1000);
-			error = RTAS_CLOCK_BUSY;
 		}
-	} while (error == RTAS_CLOCK_BUSY && (get_tb() < max_wait_tb));
+	} while (wait_time && (get_tb() < max_wait_tb));
 
 	if (error != 0 && printk_ratelimit()) {
 		printk(KERN_WARNING "error: reading the clock failed (%d)\n",
@@ -44,24 +45,25 @@ unsigned long __init rtas_get_boot_time(
 void rtas_get_rtc_time(struct rtc_time *rtc_tm)
 {
         int ret[8];
-	int error, wait_time;
+	int error;
+	unsigned int wait_time;
 	u64 max_wait_tb;
 
 	max_wait_tb = get_tb() + tb_ticks_per_usec * 1000 * MAX_RTC_WAIT;
 	do {
 		error = rtas_call(rtas_token("get-time-of-day"), 0, 8, ret);
-		if (error == RTAS_CLOCK_BUSY || rtas_is_extended_busy(error)) {
+
+		wait_time = rtas_busy_delay_time(error);
+		if (wait_time) {
 			if (in_interrupt() && printk_ratelimit()) {
 				memset(rtc_tm, 0, sizeof(struct rtc_time));
 				printk(KERN_WARNING "error: reading clock"
 				       " would delay interrupt\n");
 				return;	/* delay not allowed */
 			}
-			wait_time = rtas_extended_busy_delay_time(error);
 			msleep(wait_time);
-			error = RTAS_CLOCK_BUSY;
 		}
-	} while (error == RTAS_CLOCK_BUSY && (get_tb() < max_wait_tb));
+	} while (wait_time && (get_tb() < max_wait_tb));
 
         if (error != 0 && printk_ratelimit()) {
                 printk(KERN_WARNING "error: reading the clock failed (%d)\n",
@@ -88,14 +90,14 @@ int rtas_set_rtc_time(struct rtc_time *t
 				  tm->tm_year + 1900, tm->tm_mon + 1,
 				  tm->tm_mday, tm->tm_hour, tm->tm_min,
 				  tm->tm_sec, 0);
-		if (error == RTAS_CLOCK_BUSY || rtas_is_extended_busy(error)) {
+
+		wait_time = rtas_busy_delay_time(error);
+		if (wait_time) {
 			if (in_interrupt())
 				return 1;	/* probably decrementer */
-			wait_time = rtas_extended_busy_delay_time(error);
 			msleep(wait_time);
-			error = RTAS_CLOCK_BUSY;
 		}
-	} while (error == RTAS_CLOCK_BUSY && (get_tb() < max_wait_tb));
+	} while (wait_time && (get_tb() < max_wait_tb));
 
         if (error != 0 && printk_ratelimit())
                 printk(KERN_WARNING "error: setting the clock failed (%d)\n",
diff -puN include/asm-powerpc/rtas.h~rtas_delay_reorg include/asm-powerpc/rtas.h
--- 2_6_linus/include/asm-powerpc/rtas.h~rtas_delay_reorg	2006-06-02 15:09:43.000000000 -0500
+++ 2_6_linus-johnrose/include/asm-powerpc/rtas.h	2006-06-02 15:09:43.000000000 -0500
@@ -177,12 +177,8 @@ extern unsigned long rtas_get_boot_time(
 extern void rtas_get_rtc_time(struct rtc_time *rtc_time);
 extern int rtas_set_rtc_time(struct rtc_time *rtc_time);
 
-/* Given an RTAS status code of 9900..9905 compute the hinted delay */
-unsigned int rtas_extended_busy_delay_time(int status);
-static inline int rtas_is_extended_busy(int status)
-{
-	return status >= 9900 && status <= 9909;
-}
+extern unsigned int rtas_busy_delay_time(int status);
+extern unsigned int rtas_busy_delay(int status);
 
 extern void pSeries_log_error(char *buf, unsigned int err_type, int fatal);
 
diff -puN arch/powerpc/kernel/rtas_flash.c~rtas_delay_reorg arch/powerpc/kernel/rtas_flash.c
--- 2_6_linus/arch/powerpc/kernel/rtas_flash.c~rtas_delay_reorg	2006-06-02 15:09:43.000000000 -0500
+++ 2_6_linus-johnrose/arch/powerpc/kernel/rtas_flash.c	2006-06-02 15:09:43.000000000 -0500
@@ -365,20 +365,12 @@ static int rtas_excl_release(struct inod
 
 static void manage_flash(struct rtas_manage_flash_t *args_buf)
 {
-	unsigned int wait_time;
 	s32 rc;
 
-	while (1) {
+	do
 		rc = rtas_call(rtas_token("ibm,manage-flash-image"), 1, 
 			       1, NULL, args_buf->op);
-		if (rc == RTAS_RC_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));
 
 	args_buf->status = rc;
 }
@@ -451,27 +443,18 @@ static ssize_t manage_flash_write(struct
 static void validate_flash(struct rtas_validate_flash_t *args_buf)
 {
 	int token = rtas_token("ibm,validate-flash-image");
-	unsigned int wait_time;
 	int update_results;
 	s32 rc;	
 
 	rc = 0;
-	while(1) {
+	do {
 		spin_lock(&rtas_data_buf_lock);
 		memcpy(rtas_data_buf, args_buf->buf, VALIDATE_BUF_SIZE);
 		rc = rtas_call(token, 2, 2, &update_results, 
 			       (u32) __pa(rtas_data_buf), args_buf->buf_size);
 		memcpy(args_buf->buf, rtas_data_buf, VALIDATE_BUF_SIZE);
 		spin_unlock(&rtas_data_buf_lock);
-			
-		if (rc == RTAS_RC_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));
 
 	args_buf->status = rc;
 	args_buf->update_results = update_results;

_