rtc: opal: Fix OPAL RTC driver OPAL_BUSY loops

The OPAL RTC driver does not sleep in case it gets OPAL_BUSY or
OPAL_BUSY_EVENT from firmware, which causes large scheduling
latencies, up to 50 seconds have been observed here when RTC stops
responding (BMC reboot can do it).

Fix this by converting it to the standard form OPAL_BUSY loop that
sleeps.

Fixes: 628daa8d5abf ("powerpc/powernv: Add RTC and NVRAM support plus RTAS fallbacks")
Cc: stable@vger.kernel.org # v3.2+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/platforms/powernv/opal-rtc.c b/arch/powerpc/platforms/powernv/opal-rtc.c
index f8868864f373ed5eecba333a5b1a2b83e38e0ec6..aa2a5139462ea5f6c81f51c8f025c9af84ce0be2 100644 (file)
--- a/arch/powerpc/platforms/powernv/opal-rtc.c
+++ b/arch/powerpc/platforms/powernv/opal-rtc.c
@@ -48,10 +48,12 @@ unsigned long __init opal_get_boot_time(void)
 
        while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
                rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
-               if (rc == OPAL_BUSY_EVENT)
+               if (rc == OPAL_BUSY_EVENT) {
+                       mdelay(OPAL_BUSY_DELAY_MS);
                        opal_poll_events(NULL);
-               else if (rc == OPAL_BUSY)
-                       mdelay(10);
+               } else if (rc == OPAL_BUSY) {
+                       mdelay(OPAL_BUSY_DELAY_MS);
+               }
        }
        if (rc != OPAL_SUCCESS)
                return 0;

diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c
index 304e891e35fcb060a8ff26f78122fa3c63a1eb87..60f2250fd96bec2cec1dd33f652edaac474d2182 100644 (file)
--- a/drivers/rtc/rtc-opal.c
+++ b/drivers/rtc/rtc-opal.c
@@ -57,7 +57,7 @@ static void tm_to_opal(struct rtc_time *tm, u32 *y_m_d, u64 *h_m_s_ms)
 
 static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
 {
-       long rc = OPAL_BUSY;
+       s64 rc = OPAL_BUSY;
        int retries = 10;
        u32 y_m_d;
        u64 h_m_s_ms;
@@ -66,13 +66,17 @@ static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
 
        while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
                rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
-               if (rc == OPAL_BUSY_EVENT)
+               if (rc == OPAL_BUSY_EVENT) {
+                       msleep(OPAL_BUSY_DELAY_MS);
                        opal_poll_events(NULL);
-               else if (retries-- && (rc == OPAL_HARDWARE
-                                      || rc == OPAL_INTERNAL_ERROR))
-                       msleep(10);
-               else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)
-                       break;
+               } else if (rc == OPAL_BUSY) {
+                       msleep(OPAL_BUSY_DELAY_MS);
+               } else if (rc == OPAL_HARDWARE || rc == OPAL_INTERNAL_ERROR) {
+                       if (retries--) {
+                               msleep(10); /* Wait 10ms before retry */
+                               rc = OPAL_BUSY; /* go around again */
+                       }
+               }
        }
 
        if (rc != OPAL_SUCCESS)
@@ -87,21 +91,26 @@ static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
 
 static int opal_set_rtc_time(struct device *dev, struct rtc_time *tm)
 {
-       long rc = OPAL_BUSY;
+       s64 rc = OPAL_BUSY;
        int retries = 10;
        u32 y_m_d = 0;
        u64 h_m_s_ms = 0;
 
        tm_to_opal(tm, &y_m_d, &h_m_s_ms);
+
        while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
                rc = opal_rtc_write(y_m_d, h_m_s_ms);
-               if (rc == OPAL_BUSY_EVENT)
+               if (rc == OPAL_BUSY_EVENT) {
+                       msleep(OPAL_BUSY_DELAY_MS);
                        opal_poll_events(NULL);
-               else if (retries-- && (rc == OPAL_HARDWARE
-                                      || rc == OPAL_INTERNAL_ERROR))
-                       msleep(10);
-               else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)
-                       break;
+               } else if (rc == OPAL_BUSY) {
+                       msleep(OPAL_BUSY_DELAY_MS);
+               } else if (rc == OPAL_HARDWARE || rc == OPAL_INTERNAL_ERROR) {
+                       if (retries--) {
+                               msleep(10); /* Wait 10ms before retry */
+                               rc = OPAL_BUSY; /* go around again */
+                       }
+               }
        }
 
        return rc == OPAL_SUCCESS ? 0 : -EIO;