From b8bd146d38da5f4e683929412d59f93ad4d961c5 Mon Sep 17 00:00:00 2001 From: Jeremy Kerr Date: Mon, 12 Feb 2018 15:45:42 +1030 Subject: fsi: master-gpio: Add external mode This change introduces an 'external mode' for GPIO-based FSI masters, allowing the clock and data lines to be driven by an external source. For example, external mode is selected by a user when an external debug device is attached to the FSI pins. To do this, we need to set specific states for the trans, mux and enable GPIOs, and prevent access to clk & data from the FSI core code (by returning EBUSY). External mode is controlled by a sysfs attribute, so add the relevant information to Documentation/ABI/ Signed-off-by: Jeremy Kerr Reviewed-by: Joel Stanley Signed-off-by: Joel Stanley Signed-off-by: Greg Kroah-Hartman --- Documentation/ABI/testing/sysfs-driver-fsi-master-gpio | 10 ++++++++++ 1 file changed, 10 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-driver-fsi-master-gpio (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-driver-fsi-master-gpio b/Documentation/ABI/testing/sysfs-driver-fsi-master-gpio new file mode 100644 index 000000000000..1f29c8843cfd --- /dev/null +++ b/Documentation/ABI/testing/sysfs-driver-fsi-master-gpio @@ -0,0 +1,10 @@ +What: /sys/bus/platform/devices/[..]/fsi-master-gpio/external_mode +Date: Feb 2018 +KernelVersion: 4.17 +Contact: jk@ozlabs.org +Description: + Controls access arbitration for GPIO-based FSI master. A + value of 0 (the default) sets normal mode, where the + driver performs FSI bus transactions, 1 sets external mode, + where the FSI bus is driven externally (for example, by + a debug device). -- cgit