1 files changed, 130 insertions, 0 deletions

diff --git a/Documentation/misc-devices/spear-pcie-gadget.txt b/Documentation/misc-devices/spear-pcie-gadget.txt
new file mode 100644
index 000000000000..02c13ef5e908
--- /dev/null
+++ b/Documentation/misc-devices/spear-pcie-gadget.txt
@@ -0,0 +1,130 @@
+Spear PCIe Gadget Driver:
+
+Author
+=============
+Pratyush Anand (pratyush.anand@st.com)
+
+Location
+============
+driver/misc/spear13xx_pcie_gadget.c
+
+Supported Chip:
+===================
+SPEAr1300
+SPEAr1310
+
+Menuconfig option:
+==========================
+Device Drivers
+        Misc devices
+                PCIe gadget support for SPEAr13XX platform
+purpose
+===========
+This driver has several nodes which can be read/written by configfs interface.
+Its main purpose is to configure selected dual mode PCIe controller as device
+and then program its various registers to configure it as a particular device
+type. This driver can be used to show spear's PCIe device capability.
+
+Description of different nodes:
+=================================
+
+read behavior of nodes:
+------------------------------
+link            :gives ltssm status.
+int_type        :type of supported interrupt
+no_of_msi       :zero if MSI is not enabled by host. A positive value is the
+                number of MSI vector granted.
+vendor_id       :returns programmed vendor id (hex)
+device_id       :returns programmed device id(hex)
+bar0_size:      :returns size of bar0 in hex.
+bar0_address    :returns address of bar0 mapped area in hex.
+bar0_rw_offset  :returns offset of bar0 for which bar0_data will return value.
+bar0_data       :returns data at bar0_rw_offset.
+
+write behavior of nodes:
+------------------------------
+link            :write UP to enable ltsmm DOWN to disable
+int_type        :write interrupt type to be configured and (int_type could be
+                INTA, MSI or NO_INT). Select MSI only when you have programmed
+                no_of_msi node.
+no_of_msi       :number of MSI vector needed.
+inta            :write 1 to assert INTA and 0 to de-assert.
+send_msi        :write MSI vector to be sent.
+vendor_id       :write vendor id(hex) to be programmed.
+device_id       :write device id(hex) to be programmed.
+bar0_size       :write size of bar0 in hex. default bar0 size is 1000 (hex)
+                bytes.
+bar0_address    :write  address of bar0 mapped area in hex. (default mapping of
+                bar0 is SYSRAM1(E0800000). Always program bar size before bar
+                address. Kernel might modify bar size and address for alignment, so
+                read back bar size and address after writing to cross check.
+bar0_rw_offset  :write offset of bar0 for which bar0_data will write value.
+bar0_data       :write data to be written at bar0_rw_offset.
+
+Node programming example
+===========================
+Program all PCIe registers in such a way that when this device is connected
+to the PCIe host, then host sees this device as 1MB RAM.
+#mount -t configfs none /Config
+For nth PCIe Device Controller
+# cd /config/pcie_gadget.n/
+Now you have all the nodes in this directory.
+program vendor id as 0x104a
+# echo 104A >> vendor_id
+
+program device id as 0xCD80
+# echo CD80 >> device_id
+
+program BAR0 size as 1MB
+# echo 100000 >> bar0_size
+
+check for programmed bar0 size
+# cat bar0_size
+
+Program BAR0 Address as DDR (0x2100000). This is the physical address of
+memory, which is to be made visible to PCIe host. Similarly any other peripheral
+can also be made visible to PCIe host. E.g., if you program base address of UART
+as BAR0 address then when this device will be connected to a host, it will be
+visible as UART.
+# echo 2100000 >> bar0_address
+
+program interrupt type : INTA
+# echo INTA >> int_type
+
+go for link up now.
+# echo UP >> link
+
+It will have to be insured that, once link up is done on gadget, then only host
+is initialized and start to search PCIe devices on its port.
+
+/*wait till link is up*/
+# cat link
+wait till it returns UP.
+
+To assert INTA
+# echo 1 >> inta
+
+To de-assert INTA
+# echo 0 >> inta
+
+if MSI is to be used as interrupt, program no of msi vector needed (say4)
+# echo 4 >> no_of_msi
+
+select MSI as interrupt type
+# echo MSI >> int_type
+
+go for link up now
+# echo UP >> link
+
+wait till link is up
+# cat link
+An application can repetitively read this node till link is found UP. It can
+sleep between two read.
+
+wait till msi is enabled
+# cat no_of_msi
+Should return 4 (number of requested MSI vector)
+
+to send msi vector 2
+# echo 2 >> send_msi
+#cd -