diff options
author | Simon Glass <sjg@chromium.org> | 2016-09-05 11:10:26 -0600 |
---|---|---|
committer | Patrick Georgi <pgeorgi@google.com> | 2016-10-06 21:50:26 +0200 |
commit | 74fedbe3771febf7702a30fc4aa2e039040ff908 (patch) | |
tree | 17784c012e40946abe1b874f3af625bd1ef19d89 /src/mainboard/google | |
parent | 8e09de297fce1de0693d2833d7a15f76fa2ce18a (diff) |
rockchip: spi: Add support for 16-bit APB reads
With a SPI clock above about 24MHz the APB cannot keep up when doing
individual byte transfers. Adjust the driver to use 16-bit reads when
it can, to remove this bottleneck.
Any transaction which involves writing bytes still uses 8-bit transfers,
to simplify the code. These are the transfers that are not time-critical
since they tend to be small. The case that really matters is reading from
SPI flash.
In general we can use 16-bit reads anytime we are transferring an even
number of bytes. If the code detects an odd number of bytes, it tries to
perform the operation in two steps: once in 16-bit mode with an even
number of bytes, and once in 8-bit mode for the final byte. This allow
us to use 16-bit reads even if asked to transfer (for example) 0xf423
bytes.
The limit on in_now and out_now is adjusted to 0xfffe to avoid an extra
transfer when transferring ~>=64KB.
CQ-DEPEND=CL:383232
BUG=chrome-os-partner:56556
BRANCH=none
TEST=boot on gru and see that things still work correctly. I tested (with
extra debugging) that the 16-bit case is being picked when it should be.
Change-Id: If5effae9a84e4de06537fd594bedf7f01d6a9c88
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: ec250b4931c7d99cc014e32ab597fca948299d08
Original-Change-Id: Idc5b7e5d82cdbdc1e8fe8b2d6da819edf2d5570c
Original-Signed-off-by: Simon Glass <sjg@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/381312
Original-Commit-Ready: Julius Werner <jwerner@chromium.org>
Original-Tested-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/16712
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
Diffstat (limited to 'src/mainboard/google')
0 files changed, 0 insertions, 0 deletions