flash/nor/at91samd: Use 32-bit register writes for ST-Link compat
commitaf75d70dc5e6d83c57c6e8ee1a23ef9b472d2d52
authorKeith Packard <keithp@keithp.com>
Wed, 28 Sep 2022 21:02:52 +0000 (28 14:02 -0700)
committerAntonio Borneo <borneo.antonio@gmail.com>
Sat, 8 Oct 2022 07:52:28 +0000 (8 07:52 +0000)
treed3694c13fbc70c484e67dee0c975bbf36150489a
parent0cedf10f8fd618b78190ce32a40f26dec0fb8253
flash/nor/at91samd: Use 32-bit register writes for ST-Link compat

ST-Link v2 dongles can be used with many cortex-m parts, but they have
one limitation -- they can only perform 8-bit and 32-bit writes to the
target. 16-bit writes are done using a pair of 8-bit writes. While not
usually an issue, in the case of the at91samd flash driver, the 16-bit
'command' register must have both halves written in the same
operation.

Fortunately, this register has two pad bytes above it in the address
space, making it safe to always access with 32-bit operations.

Change-Id: I44b0db9406982a8db5818c0533d3101618741db2
Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7234
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
src/flash/nor/at91samd.c