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author | Adrian Schmutzler <freifunk@adrianschmutzler.de> | 2020-02-27 11:55:36 +0100 |
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committer | Adrian Schmutzler <freifunk@adrianschmutzler.de> | 2020-02-27 12:14:09 +0100 |
commit | ebc090e420d1fc3ed30fc9f0331ee95422c2bace (patch) | |
tree | 48fd8b997020c7ecb15f8e00937a5c6087adac1e /toolchain | |
parent | 9de6bc872af50c80f0ba449422f413cfa613f7e5 (diff) | |
download | upstream-ebc090e420d1fc3ed30fc9f0331ee95422c2bace.tar.gz upstream-ebc090e420d1fc3ed30fc9f0331ee95422c2bace.tar.bz2 upstream-ebc090e420d1fc3ed30fc9f0331ee95422c2bace.zip |
ath79: reduce spi-max-frequency to 50 MHz
The introduction of ebf0d8dadeca ("ath79: add new ar934x spi driver")
made the SPI memory unusable on devices with very high spi-max-frequency
(104 MHz).
Here's how the actual clock is calculated: (AHB_CLK/((CLOCK_DIVIDER+1)*2))
where AHB_CLK is a fixed clock (e.g. 200MHz on AR9331) and CLOCK_DIVIDER
is the parameter we can set. Highest clock according to this formula is
AHB_CLK/2 (100MHz, but that didn't work in device tests).
The next possible value is AHB_CLK/4 (50MHz). Speeds between 50 MHz and
100 MHz will be rounded down, so using values higher than 50 MHz does
not provide any benefit.
Consequently, this patch reduces spi-max-frequency for all devices with
values higher than 50 MHz to 50 MHz (effectively, this only affects
devices with 104 MHz before this patch).
Tested on GL.inet GL-AR150:
Boot fails with 104 MHz but is successful with both 50 MHz and 80 MHz
(fast-read), where the latter two yield identical read speeds.
Fixes: ebf0d8dadeca ("ath79: add new ar934x spi driver")
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Diffstat (limited to 'toolchain')
0 files changed, 0 insertions, 0 deletions