linux/arch/arm/mach-shmobile
Geert Uytterhoeven c531fb27e9 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>
2016-04-20 08:52:55 +10:00
..
2016-03-20 14:57:08 -07:00
2015-09-08 14:35:59 -07:00
2016-03-20 14:57:08 -07:00