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diff --git a/Documentation/misc-devices/spear-pcie-gadget.rst b/Documentation/misc-devices/spear-pcie-gadget.rst new file mode 100644 index 000000000000..09b9d6c7ac15 --- /dev/null +++ b/Documentation/misc-devices/spear-pcie-gadget.rst @@ -0,0 +1,170 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +Spear PCIe Gadget Driver +======================== + +Author +====== +Pratyush Anand (pratyush.anand@gmail.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 - |