cxl: Add documentation for userspace APIs

This documentation gives an overview of the hardware architecture, userspace
APIs via /dev/cxl/afuM.N and the syfs files. It also adds a MAINTAINERS file
entry for cxl.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Documentation/ABI/testing/sysfs-class-cxl

@@ -0,0 +1,129 @@
+Slave contexts (eg. /sys/class/cxl/afu0.0s):
+
+What:           /sys/class/cxl/<afu>/irqs_max
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read/write
+                Decimal value of maximum number of interrupts that can be
+                requested by userspace.  The default on probe is the maximum
+                that hardware can support (eg. 2037). Write values will limit
+                userspace applications to that many userspace interrupts. Must
+                be >= irqs_min.
+
+What:           /sys/class/cxl/<afu>/irqs_min
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the minimum number of interrupts that
+                userspace must request on a CXL_START_WORK ioctl. Userspace may
+                omit the num_interrupts field in the START_WORK IOCTL to get
+                this minimum automatically.
+
+What:           /sys/class/cxl/<afu>/mmio_size
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the size of the MMIO space that may be mmaped
+                by userspace.
+
+What:           /sys/class/cxl/<afu>/modes_supported
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                List of the modes this AFU supports. One per line.
+                Valid entries are: "dedicated_process" and "afu_directed"
+
+What:           /sys/class/cxl/<afu>/mode
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read/write
+                The current mode the AFU is using. Will be one of the modes
+                given in modes_supported. Writing will change the mode
+                provided that no user contexts are attached.
+
+
+What:           /sys/class/cxl/<afu>/prefault_mode
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read/write
+                Set the mode for prefaulting in segments into the segment table
+                when performing the START_WORK ioctl. Possible values:
+                        none: No prefaulting (default)
+                        work_element_descriptor: Treat the work element
+                                 descriptor as an effective address and
+                                 prefault what it points to.
+                        all: all segments process calling START_WORK maps.
+
+What:           /sys/class/cxl/<afu>/reset
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    write only
+                Writing 1 here will reset the AFU provided there are not
+                contexts active on the AFU.
+
+What:           /sys/class/cxl/<afu>/api_version
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the current version of the kernel/user API.
+
+What:           /sys/class/cxl/<afu>/api_version_com
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the the lowest version of the userspace API
+                this this kernel supports.
+
+
+
+Master contexts (eg. /sys/class/cxl/afu0.0m)
+
+What:           /sys/class/cxl/<afu>m/mmio_size
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the size of the MMIO space that may be mmaped
+                by userspace. This includes all slave contexts space also.
+
+What:           /sys/class/cxl/<afu>m/pp_mmio_len
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the Per Process MMIO space length.
+
+What:           /sys/class/cxl/<afu>m/pp_mmio_off
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Decimal value of the Per Process MMIO space offset.
+
+
+Card info (eg. /sys/class/cxl/card0)
+
+What:           /sys/class/cxl/<card>/caia_version
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Identifies the CAIA Version the card implements.
+
+What:           /sys/class/cxl/<card>/psl_version
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Identifies the revision level of the PSL.
+
+What:           /sys/class/cxl/<card>/base_image
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Identifies the revision level of the base image for devices
+                that support loadable PSLs. For FPGAs this field identifies
+                the image contained in the on-adapter flash which is loaded
+                during the initial program load.
+
+What:           /sys/class/cxl/<card>/image_loaded
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                Will return "user" or "factory" depending on the image loaded
+                onto the card.

Documentation/ioctl/ioctl-number.txt

@@ -313,6 +313,7 @@ Code  Seq#(hex)	Include File		Comments
 0xB1	00-1F	PPPoX			<mailto:mostrows@styx.uwaterloo.ca>
 0xB3	00	linux/mmc/ioctl.h
 0xC0	00-0F	linux/usb/iowarrior.h
+0xCA	00-0F	uapi/misc/cxl.h
 0xCB	00-1F	CBM serial IEC bus	in development:
 					<mailto:michael.klein@puffin.lb.shuttle.de>
 0xCD	01	linux/reiserfs_fs.h

Documentation/powerpc/00-INDEX

@@ -11,6 +11,8 @@ bootwrapper.txt
 cpu_features.txt
 	- info on how we support a variety of CPUs with minimal compile-time
 	options.
+cxl.txt
+	- Overview of the CXL driver.
 eeh-pci-error-recovery.txt
 	- info on PCI Bus EEH Error Recovery
 firmware-assisted-dump.txt