ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 56 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-css b/Documentation/ABI/testing/sysfs-bus-css
new file mode 100644
index 000000000..d4d5cfb63
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-css
@@ -0,0 +1,56 @@
+What:		/sys/bus/css/devices/.../type
+Date:		March 2008
+Contact:	linux-s390@vger.kernel.org
+Description:	Contains the subchannel type, as reported by the hardware.
+		This attribute is present for all subchannel types.
+
+What:		/sys/bus/css/devices/.../modalias
+Date:		March 2008
+Contact:	linux-s390@vger.kernel.org
+Description:	Contains the module alias as reported with uevents.
+		It is of the format css:t<type> and present for all
+		subchannel types.
+
+What:		/sys/bus/css/drivers/io_subchannel/.../chpids
+Date:		December 2002
+Contact:	linux-s390@vger.kernel.org
+Description:	Contains the ids of the channel paths used by this
+		subchannel, as reported by the channel subsystem
+		during subchannel recognition.
+
+		Note: This is an I/O-subchannel specific attribute.
+Users:		s390-tools, HAL
+
+What:		/sys/bus/css/drivers/io_subchannel/.../pimpampom
+Date:		December 2002
+Contact:	linux-s390@vger.kernel.org
+Description:	Contains the PIM/PAM/POM values, as reported by the
+		channel subsystem when last queried by the common I/O
+		layer (this implies that this attribute is not necessarily
+		in sync with the values current in the channel subsystem).
+
+		Note: This is an I/O-subchannel specific attribute.
+Users:		s390-tools, HAL
+
+What:		/sys/bus/css/devices/.../driver_override
+Date:		June 2019
+Contact:	linux-s390@vger.kernel.org
+Description:	This file allows the driver for a device to be specified. When
+		specified, only a driver with a name matching the value written
+		to driver_override will have an opportunity to bind to the
+		device. The override is specified by writing a string to the
+		driver_override file (echo vfio-ccw > driver_override) and
+		may be cleared with an empty string (echo > driver_override).
+		This returns the device to standard matching rules binding.
+		Writing to driver_override does not automatically unbind the
+		device from its current driver or make any attempt to
+		automatically load the specified driver.  If no driver with a
+		matching name is currently loaded in the kernel, the device
+		will not bind to any driver.  This also allows devices to
+		opt-out of driver binding using a driver_override name such as
+		"none".  Only a single driver may be specified in the override,
+		there is no support for parsing delimiters.
+
+		Note that unlike the mechanism of the same name for pci, this
+		file does not allow to override basic matching rules. I.e.,
+		the driver must still match the subchannel type of the device.