Merge tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timers and timekeeping updates from Thomas Gleixner:
 "Core:

   - Robustness improvements for the NOHZ tick management

   - Fixes and consolidation of the NTP/RTC synchronization code

   - Small fixes and improvements in various places

   - A set of function documentation udpates and fixes

   Drivers:

   - Cleanups and improvements in various clocksoure/event drivers

   - Removal of the EZChip NPS clocksource driver as the platfrom
     support was removed from ARC

   - The usual set of new device tree binding and json conversions

   - The RTC driver which have been acked by the RTC maintainer:

       * fix a long standing bug in the MC146818 library code which can
         cause reading garbage during the RTC internal update.

       * changes related to the NTP/RTC consolidation work"

* tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits)
  ntp: Fix prototype in the !CONFIG_GENERIC_CMOS_UPDATE case
  tick/sched: Make jiffies update quick check more robust
  ntp: Consolidate the RTC update implementation
  ntp: Make the RTC sync offset less obscure
  ntp, rtc: Move rtc_set_ntp_time() to ntp code
  ntp: Make the RTC synchronization more reliable
  rtc: core: Make the sync offset default more realistic
  rtc: cmos: Make rtc_cmos sync offset correct
  rtc: mc146818: Reduce spinlock section in mc146818_set_time()
  rtc: mc146818: Prevent reading garbage
  clocksource/drivers/sh_cmt: Fix potential deadlock when calling runtime PM
  clocksource/drivers/arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI
  clocksource/drivers/arm_arch_timer: Use stable count reader in erratum sne
  clocksource/drivers/dw_apb_timer_of: Add error handling if no clock available
  clocksource/drivers/riscv: Make RISCV_TIMER depends on RISCV_SBI
  clocksource/drivers/ingenic: Fix section mismatch
  clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent()
  dt-bindings: timer: renesas: tmu: Convert to json-schema
  dt-bindings: timer: renesas: tmu: Document r8a774e1 bindings
  clocksource/drivers/orion: Add missing clk_disable_unprepare() on error path
  ...

5 files changed, 51 insertions, 93 deletions

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index bfb57464118d..bb8f319b09fb 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -6,7 +6,6 @@
 ccflags-$(CONFIG_RTC_DEBUG)	:= -DDEBUG
 
 obj-$(CONFIG_RTC_LIB)		+= lib.o
-obj-$(CONFIG_RTC_SYSTOHC)	+= systohc.o
 obj-$(CONFIG_RTC_CLASS)		+= rtc-core.o
 obj-$(CONFIG_RTC_MC146818_LIB)	+= rtc-mc146818-lib.o
 rtc-core-y			:= class.o interface.o
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 7c88d190c51f..5855aa2eef62 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -200,8 +200,13 @@ static struct rtc_device *rtc_allocate_device(void)
 
 	device_initialize(&rtc->dev);
 
-	/* Drivers can revise this default after allocating the device. */
-	rtc->set_offset_nsec =  NSEC_PER_SEC / 2;
+	/*
+	 * Drivers can revise this default after allocating the device.
+	 * The default is what most RTCs do: Increment seconds exactly one
+	 * second after the write happened. This adds a default transport
+	 * time of 5ms which is at least halfways close to reality.
+	 */
+	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
 
 	rtc->irq_freq = 1;
 	rtc->max_user_freq = 64;
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index c633319cdb91..c5bcd2adc9fe 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -868,6 +868,9 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 	if (retval)
 		goto cleanup2;
 
+	/* Set the sync offset for the periodic 11min update correct */
+	cmos_rtc.rtc->set_offset_nsec = NSEC_PER_SEC / 2;
+
 	/* export at least the first block of NVRAM */
 	nvmem_cfg.size = address_space - NVRAM_OFFSET;
 	if (rtc_nvmem_register(cmos_rtc.rtc, &nvmem_cfg))
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 2ecd8752b088..972a5b9a629d 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -8,41 +8,41 @@
 #include <linux/acpi.h>
 #endif
 
-/*
- * Returns true if a clock update is in progress
- */
-static inline unsigned char mc146818_is_updating(void)
-{
-	unsigned char uip;
-	unsigned long flags;
-
-	spin_lock_irqsave(&rtc_lock, flags);
-	uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
-	spin_unlock_irqrestore(&rtc_lock, flags);
-	return uip;
-}
-
 unsigned int mc146818_get_time(struct rtc_time *time)
 {
 	unsigned char ctrl;
 	unsigned long flags;
 	unsigned char century = 0;
+	bool retry;
 
 #ifdef CONFIG_MACH_DECSTATION
 	unsigned int real_year;
 #endif
 
+again:
+	spin_lock_irqsave(&rtc_lock, flags);
 	/*
-	 * read RTC once any update in progress is done. The update
-	 * can take just over 2ms. We wait 20ms. There is no need to
-	 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
-	 * If you need to know *exactly* when a second has started, enable
-	 * periodic update complete interrupts, (via ioctl) and then
-	 * immediately read /dev/rtc which will block until you get the IRQ.
-	 * Once the read clears, read the RTC time (again via ioctl). Easy.
+	 * Check whether there is an update in progress during which the
+	 * readout is unspecified. The maximum update time is ~2ms. Poll
+	 * every msec for completion.
+	 *
+	 * Store the second value before checking UIP so a long lasting NMI
+	 * which happens to hit after the UIP check cannot make an update
+	 * cycle invisible.
 	 */
-	if (mc146818_is_updating())
-		mdelay(20);
+	time->tm_sec = CMOS_READ(RTC_SECONDS);
+
+	if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
+		spin_unlock_irqrestore(&rtc_lock, flags);
+		mdelay(1);
+		goto again;
+	}
+
+	/* Revalidate the above readout */
+	if (time->tm_sec != CMOS_READ(RTC_SECONDS)) {
+		spin_unlock_irqrestore(&rtc_lock, flags);
+		goto again;
+	}
 
 	/*
 	 * Only the values that we read from the RTC are set. We leave
@@ -50,8 +50,6 @@ unsigned int mc146818_get_time(struct rtc_time *time)
 	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
 	 * by the RTC when initially set to a non-zero value.
 	 */
-	spin_lock_irqsave(&rtc_lock, flags);
-	time->tm_sec = CMOS_READ(RTC_SECONDS);
 	time->tm_min = CMOS_READ(RTC_MINUTES);
 	time->tm_hour = CMOS_READ(RTC_HOURS);
 	time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
@@ -66,8 +64,24 @@ unsigned int mc146818_get_time(struct rtc_time *time)
 		century = CMOS_READ(acpi_gbl_FADT.century);
 #endif
 	ctrl = CMOS_READ(RTC_CONTROL);
+	/*
+	 * Check for the UIP bit again. If it is set now then
+	 * the above values may contain garbage.
+	 */
+	retry = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
+	/*
+	 * A NMI might have interrupted the above sequence so check whether
+	 * the seconds value has changed which indicates that the NMI took
+	 * longer than the UIP bit was set. Unlikely, but possible and
+	 * there is also virt...
+	 */
+	retry |= time->tm_sec != CMOS_READ(RTC_SECONDS);
+
 	spin_unlock_irqrestore(&rtc_lock, flags);
 
+	if (retry)
+		goto again;
+
 	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 	{
 		time->tm_sec = bcd2bin(time->tm_sec);
@@ -121,7 +135,6 @@ int mc146818_set_time(struct rtc_time *time)
 	if (yrs > 255)	/* They are unsigned */
 		return -EINVAL;
 
-	spin_lock_irqsave(&rtc_lock, flags);
 #ifdef CONFIG_MACH_DECSTATION
 	real_yrs = yrs;
 	leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
@@ -150,10 +163,8 @@ int mc146818_set_time(struct rtc_time *time)
 	/* These limits and adjustments are independent of
 	 * whether the chip is in binary mode or not.
 	 */
-	if (yrs > 169) {
-		spin_unlock_irqrestore(&rtc_lock, flags);
+	if (yrs > 169)
 		return -EINVAL;
-	}
 
 	if (yrs >= 100)
 		yrs -= 100;
@@ -169,6 +180,7 @@ int mc146818_set_time(struct rtc_time *time)
 		century = bin2bcd(century);
 	}
 
+	spin_lock_irqsave(&rtc_lock, flags);
 	save_control = CMOS_READ(RTC_CONTROL);
 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
 	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
diff --git a/drivers/rtc/systohc.c b/drivers/rtc/systohc.c
deleted file mode 100644
index 8b70f0520e13..000000000000
--- a/drivers/rtc/systohc.c
+++ /dev/null
@@ -1,61 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <linux/rtc.h>
-#include <linux/time.h>
-
-/**
- * rtc_set_ntp_time - Save NTP synchronized time to the RTC
- * @now: Current time of day
- * @target_nsec: pointer for desired now->tv_nsec value
- *
- * Replacement for the NTP platform function update_persistent_clock64
- * that stores time for later retrieval by rtc_hctosys.
- *
- * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
- * possible at all, and various other -errno for specific temporary failure
- * cases.
- *
- * -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
- *
- * If temporary failure is indicated the caller should try again 'soon'
- */
-int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
-{
-	struct rtc_device *rtc;
-	struct rtc_time tm;
-	struct timespec64 to_set;
-	int err = -ENODEV;
-	bool ok;
-
-	rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
-	if (!rtc)
-		goto out_err;
-
-	if (!rtc->ops || !rtc->ops->set_time)
-		goto out_close;
-
-	/* Compute the value of tv_nsec we require the caller to supply in
-	 * now.tv_nsec.  This is the value such that (now +
-	 * set_offset_nsec).tv_nsec == 0.
-	 */
-	set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
-	*target_nsec = to_set.tv_nsec;
-
-	/* The ntp code must call this with the correct value in tv_nsec, if
-	 * it does not we update target_nsec and return EPROTO to make the ntp
-	 * code try again later.
-	 */
-	ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
-	if (!ok) {
-		err = -EPROTO;
-		goto out_close;
-	}
-
-	rtc_time64_to_tm(to_set.tv_sec, &tm);
-
-	err = rtc_set_time(rtc, &tm);
-
-out_close:
-	rtc_class_close(rtc);
-out_err:
-	return err;
-}