The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 682e6b4da5cbe8e9a53f979a58c2a9d7dc997175 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin npiggin@gmail.com Date: Tue, 10 Apr 2018 21:49:32 +1000 Subject: [PATCH] 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 f8868864f373..aa2a5139462e 100644 --- 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 304e891e35fc..60f2250fd96b 100644 --- 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;