summaryrefslogtreecommitdiff
path: root/payloads
diff options
context:
space:
mode:
authorHung-Te Lin <hungte@chromium.org>2019-09-19 11:23:30 +0800
committerPatrick Georgi <pgeorgi@google.com>2019-09-24 10:32:50 +0000
commit0962b1fa5d3f7a165c9b427faab76c45989d9b40 (patch)
tree939db5d56d9cf68304808c50fb2e1578d622f4a5 /payloads
parentb5598cee7ede891d4f05aa9105cca87c11f0ff28 (diff)
downloadcoreboot-0962b1fa5d3f7a165c9b427faab76c45989d9b40.tar.xz
device/mmio.h: Add bit field helpers
When accessing register with multiple bit fields, the common approach is to use clrsetbits_le32, for example: clrsetbits(&reg, (1 << 0) | (0x3 << 1) | (0x7 << 10), (1 << 0) | (0x1 << 1) | (0x5 << 10)); This hard to maintain because we have to calculate the mask values manually, make sure the duplicated shift (offset) was set correctly. And it may be even worse if the value to set will be based on some runtime values (that many developers will do a if-block with two very similar argument list), and leaving lots of magic numbers. We want to encourage developers always giving field names, and have a better way of setting fields. The proposed utility macros are: DEFINE_BITFIELD(name, high_bit, low_bit) EXTRACT_BITFIELD(value, name) WRITE32_BITFIELDS(addr, name, value, [name2, value2, ...]) READ32_BITFIELD(addr, name) Where a developer can easily convert from data sheet like BITS NAME 26:24 SEC_VIO Into a declaration DEFINE_BITFIELD(SEC_VIO, 26, 24) Then, a simple call can set the field as: WRITE32_BITFIELDS(&reg, SEC_VIO, 2); That is much easier to understand than clrsetbits_le32(&reg, 0x7 << 24, 0x2 << 24); And to extract the value: READ32_BITFIELD(&reg, SEC_VIO) That is equivalent to: (read32(&reg) & 0x3) >> 24 Change-Id: I8a1b17142f7a7dc6c441b0b1ee67d60d73ec8cc8 Signed-off-by: Hung-Te Lin <hungte@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/35463 Reviewed-by: Julius Werner <jwerner@chromium.org> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Diffstat (limited to 'payloads')
0 files changed, 0 insertions, 0 deletions