Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrlgrafted

Pull pin control updates from Linus Walleij:
 "Core changes:

   - Use the non-blocking mux_state_try_select() in the generic MUX pin
     control back-end

   - Free pin maps on pinctrl_generic_to_map() failure in the core
     helpers

  New hardware pin control:

   - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC
     (this is for the low power audio, LPASS = Low Power Audio SubSystem
     portions)

   - Upboard support on top of the Intel pin controller

   - Apple T6030 and T6031 support (just compatible strings)

   - Samsung Exynos 8855 SoC

   - Mediatek MT6858 SoC

   - Rockchip RK3308B and RV1106 SoCs

   - Airoha EN7523 and AN7563 SoCs

  Improvements:

   - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable

   - Qualcomm improvements on top of the Qualcomm PDC (power domain
     controller) irqchip improvements from tglx:s tree

   - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups

   - The NPCM8xx driver has been put into shape fixing many pin and
     group definitions

   - Some non-urgent Tegra 264 pin assignments are fixed up

   - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and
     pin assignments, missing features etc"

* tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits)
  dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema
  pinctrl: meson: sync some modify from A4
  pinctrl: meson: a4: Add input enable pin configuration
  pinctrl: realtek: rtd1625: remove unused group name spdif_sel
  pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13
  dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema
  Revert "Merge branch 'ib-rsk7204' into devel"
  pinctrl: rockchip: Add RV1106 pinctrl support
  dt-bindings: pinctrl: rockchip: Add RV1106 compatible
  pinctrl: rockchip: Decode drive strength in the get function
  pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable
  pinctrl: airoha: add support of an7563 SoC
  dt-bindings: pinctrl: airoha: add support of an7563 pin controller
  pinctrl: airoha: try to find chip scu node by phandle first
  pinctrl: airoha: add support of en7523 SoC
  dt-bindings: pinctrl: airoha: add support of en7523 pin controller
  pinctrl: airoha: an7583: add support for olt pinmux
  pinctrl: airoha: an7583: add support for pon_alt pinmux
  pinctrl: airoha: an7583: add support for npu_uart pinmux
  dt-bindings: pinctrl: airoha: an7583: add missed features
  ...

1 files changed, 140 insertions, 0 deletions

diff --git a/Documentation/admin-guide/rtc.rst b/Documentation/admin-guide/rtc.rst
new file mode 100644
index 000000000..688c95b11
--- /dev/null
+++ b/Documentation/admin-guide/rtc.rst
@@ -0,0 +1,140 @@
+=======================================
+Real Time Clock (RTC) Drivers for Linux
+=======================================
+
+When Linux developers talk about a "Real Time Clock", they usually mean
+something that tracks wall clock time and is battery backed so that it
+works even with system power off.  Such clocks will normally not track
+the local time zone or daylight savings time -- unless they dual boot
+with MS-Windows -- but will instead be set to Coordinated Universal Time
+(UTC, formerly "Greenwich Mean Time").
+
+The newest non-PC hardware tends to just count seconds, like the time(2)
+system call reports, but RTCs also very commonly represent time using
+the Gregorian calendar and 24 hour time, as reported by gmtime(3).
+
+Linux has two largely-compatible userspace RTC API families you may
+need to know about:
+
+    *	/dev/rtc ... is the RTC provided by PC compatible systems,
+	so it's not very portable to non-x86 systems.
+
+    *	/dev/rtc0, /dev/rtc1 ... are part of a framework that's
+	supported by a wide variety of RTC chips on all systems.
+
+Programmers need to understand that the PC/AT functionality is not
+always available, and some systems can do much more.  That is, the
+RTCs use the same API to make requests in both RTC frameworks (using
+different filenames of course), but the hardware may not offer the
+same functionality.  For example, not every RTC is hooked up to an
+IRQ, so they can't all issue alarms; and where standard PC RTCs can
+only issue an alarm up to 24 hours in the future, other hardware may
+be able to schedule one any time in the upcoming century.
+
+
+Old PC/AT-Compatible driver:  /dev/rtc
+--------------------------------------
+
+All PCs (even Alpha machines) have a Real Time Clock built into them.
+Usually they are built into the chipset of the computer, but some may
+actually have a Motorola MC146818 (or clone) on the board. This is the
+clock that keeps the date and time while your computer is turned off.
+
+ACPI has standardized that MC146818 functionality, and extended it in
+a few ways (enabling longer alarm periods, and wake-from-hibernate).
+That functionality is NOT exposed in the old driver.
+
+However it can also be used to generate signals from a slow 2Hz to a
+relatively fast 8192Hz, in increments of powers of two. These signals
+are reported by interrupt number 8. (Oh! So *that* is what IRQ 8 is
+for...) It can also function as a 24hr alarm, raising IRQ 8 when the
+alarm goes off. The alarm can also be programmed to only check any
+subset of the three programmable values, meaning that it could be set to
+ring on the 30th second of the 30th minute of every hour, for example.
+The clock can also be set to generate an interrupt upon every clock
+update, thus generating a 1Hz signal.
+
+The interrupts are reported via /dev/rtc (major 10, minor 135, read only
+character device) in the form of an unsigned long. The low byte contains
+the type of interrupt (update-done, alarm-rang, or periodic) that was
+raised, and the remaining bytes contain the number of interrupts since
+the last read.  Status information is reported through the pseudo-file
+/proc/driver/rtc if the /proc filesystem was enabled.  The driver has
+built in locking so that only one process is allowed to have the /dev/rtc
+interface open at a time.
+
+A user process can monitor these interrupts by doing a read(2) or a
+select(2) on /dev/rtc -- either will block/stop the user process until
+the next interrupt is received. This is useful for things like
+reasonably high frequency data acquisition where one doesn't want to
+burn up 100% CPU by polling gettimeofday etc. etc.
+
+At high frequencies, or under high loads, the user process should check
+the number of interrupts received since the last read to determine if
+there has been any interrupt "pileup" so to speak. Just for reference, a
+typical 486-33 running a tight read loop on /dev/rtc will start to suffer
+occasional interrupt pileup (i.e. > 1 IRQ event since last read) for
+frequencies above 1024Hz. So you really should check the high bytes
+of the value you read, especially at frequencies above that of the
+normal timer interrupt, which is 100Hz.
+
+Programming and/or enabling interrupt frequencies greater than 64Hz is
+only allowed by root. This is perhaps a bit conservative, but we don't want
+an evil user generating lots of IRQs on a slow 386sx-16, where it might have
+a negative impact on performance. This 64Hz limit can be changed by writing
+a different value to /proc/sys/dev/rtc/max-user-freq. Note that the
+interrupt handler is only a few lines of code to minimize any possibility
+of this effect.
+
+Also, if the kernel time is synchronized with an external source, the 
+kernel will write the time back to the CMOS clock every 11 minutes. In 
+the process of doing this, the kernel briefly turns off RTC periodic 
+interrupts, so be aware of this if you are doing serious work. If you
+don't synchronize the kernel time with an external source (via ntp or
+whatever) then the kernel will keep its hands off the RTC, allowing you
+exclusive access to the device for your applications.
+
+The alarm and/or interrupt frequency are programmed into the RTC via
+various ioctl(2) calls as listed in ./include/linux/rtc.h
+Rather than write 50 pages describing the ioctl() and so on, it is
+perhaps more useful to include a small test program that demonstrates
+how to use them, and demonstrates the features of the driver. This is
+probably a lot more useful to people interested in writing applications
+that will be using this driver.  See the code at the end of this document.
+
+(The original /dev/rtc driver was written by Paul Gortmaker.)
+
+
+New portable "RTC Class" drivers:  /dev/rtcN
+--------------------------------------------
+
+Because Linux supports many non-ACPI and non-PC platforms, some of which
+have more than one RTC style clock, it needed a more portable solution
+than expecting a single battery-backed MC146818 clone on every system.
+Accordingly, a new "RTC Class" framework has been defined.  It offers
+three different userspace interfaces:
+
+    *	/dev/rtcN ... much the same as the older /dev/rtc interface
+
+    *	/sys/class/rtc/rtcN ... sysfs attributes support readonly
+	access to some RTC attributes.
+
+    *	/proc/driver/rtc ... the system clock RTC may expose itself
+	using a procfs interface. If there is no RTC for the system clock,
+	rtc0 is used by default. More information is (currently) shown
+	here than through sysfs.
+
+The RTC Class framework supports a wide variety of RTCs, ranging from those
+integrated into embeddable system-on-chip (SOC) processors to discrete chips
+using I2C, SPI, or some other bus to communicate with the host CPU.  There's
+even support for PC-style RTCs ... including the features exposed on newer PCs
+through ACPI.
+
+The new framework also removes the "one RTC per system" restriction.  For
+example, maybe the low-power battery-backed RTC is a discrete I2C chip, but
+a high functionality RTC is integrated into the SOC.  That system might read
+the system clock from the discrete RTC, but use the integrated one for all
+other tasks, because of its greater functionality.
+
+Check out tools/testing/selftests/rtc/rtctest.c for an example usage of the
+ioctl interface.