rtc: opal: Fix OPAL RTC driver OPAL_BUSY loops

commit 682e6b4da5cbe8e9a53f979a58c2a9d7dc997175 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/platforms/powernv/opal-rtc.c b/arch/powerpc/platforms/powernv/opal-rtc.c
index f886886..aa2a513 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 aa53fce..180ec1f 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;