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, 33 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/flashing.rst b/Documentation/gpu/amdgpu/flashing.rst
new file mode 100644
index 000000000..bd745c42a
--- /dev/null
+++ b/Documentation/gpu/amdgpu/flashing.rst
@@ -0,0 +1,33 @@
+=======================
+ dGPU firmware flashing
+=======================
+
+IFWI
+----
+Flashing the dGPU integrated firmware image (IFWI) is supported by GPUs that
+use the PSP to orchestrate the update (Navi3x or newer GPUs).
+For supported GPUs, `amdgpu` will export a series of sysfs files that can be
+used for the flash process.
+
+The IFWI flash process is:
+
+1. Ensure the IFWI image is intended for the dGPU on the system.
+2. "Write" the IFWI image to the sysfs file `psp_vbflash`. This will stage the IFWI in memory.
+3. "Read" from the `psp_vbflash` sysfs file to initiate the flash process.
+4. Poll the `psp_vbflash_status` sysfs file to determine when the flash process completes.
+
+USB-C PD F/W
+------------
+On GPUs that support flashing an updated USB-C PD firmware image, the process
+is done using the `usbc_pd_fw` sysfs file.
+
+* Reading the file will provide the current firmware version.
+* Writing the name of a firmware payload stored in `/lib/firmware/amdgpu` to the sysfs file will initiate the flash process.
+
+The firmware payload stored in `/lib/firmware/amdgpu` can be named any name
+as long as it doesn't conflict with other existing binaries that are used by
+`amdgpu`.
+
+sysfs files
+-----------
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c