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author | Geert Uytterhoeven <geert+renesas@glider.be> | 2016-01-11 19:41:12 +0100 |
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committer | Simon Horman <horms+renesas@verge.net.au> | 2016-04-20 08:52:55 +1000 |
commit | c531fb27e9699eaee478ee5686a3cca5dee73602 (patch) | |
tree | ff4a270a520ba262221fa5b0ff7b67d45d8548c2 /Documentation | |
parent | 01638a7f5ef967e94e8aff455874d62e12fe32ed (diff) |
ARM: shmobile: timer: Fix preset_lpj leading to too short delays
On all shmobile ARM SoCs, loop-based delays may complete early, which
can be after only 1/3 (Cortex A9) or 1/2 (Cortex A7 or A15) of the
minimum required time.
This is caused by calculating preset_lpj based on incorrect assumptions
about the number of clock cycles per loop:
- All of Cortex A7, A9, and A15 run __loop_delay() at 1 loop per
CPU clock cycle,
- As of commit 11d4bb1bd067f9d0 ("ARM: 7907/1: lib: delay-loop: Add
align directive to fix BogoMIPS calculation"), Cortex A8 runs
__loop_delay() at 1 loop per 2 instead of 3 CPU clock cycles.
On SoCs with Cortex A7 and/or A15 CPU cores, this went unnoticed, as
delays use the ARM arch timer if available. R-Car Gen2 doesn't work if
the arch timer is disabled. However, APE6 can be used without the arch
timer.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Diffstat (limited to 'Documentation')
0 files changed, 0 insertions, 0 deletions