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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 /arch/arm/mach-shmobile | |
parent | 01638a7f5ef967e94e8aff455874d62e12fe32ed (diff) | |
download | linux-c531fb27e9699eaee478ee5686a3cca5dee73602.tar.gz linux-c531fb27e9699eaee478ee5686a3cca5dee73602.tar.bz2 linux-c531fb27e9699eaee478ee5686a3cca5dee73602.zip |
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 'arch/arm/mach-shmobile')
-rw-r--r-- | arch/arm/mach-shmobile/timer.c | 28 |
1 files changed, 11 insertions, 17 deletions
diff --git a/arch/arm/mach-shmobile/timer.c b/arch/arm/mach-shmobile/timer.c index ad008e4b0c49..67d79f9c6bad 100644 --- a/arch/arm/mach-shmobile/timer.c +++ b/arch/arm/mach-shmobile/timer.c @@ -40,8 +40,7 @@ static void __init shmobile_setup_delay_hz(unsigned int max_cpu_core_hz, void __init shmobile_init_delay(void) { struct device_node *np, *cpus; - bool is_a7_a8_a9 = false; - bool is_a15 = false; + unsigned int div = 0; bool has_arch_timer = false; u32 max_freq = 0; @@ -55,27 +54,22 @@ void __init shmobile_init_delay(void) if (!of_property_read_u32(np, "clock-frequency", &freq)) max_freq = max(max_freq, freq); - if (of_device_is_compatible(np, "arm,cortex-a8") || - of_device_is_compatible(np, "arm,cortex-a9")) { - is_a7_a8_a9 = true; - } else if (of_device_is_compatible(np, "arm,cortex-a7")) { - is_a7_a8_a9 = true; - has_arch_timer = true; - } else if (of_device_is_compatible(np, "arm,cortex-a15")) { - is_a15 = true; + if (of_device_is_compatible(np, "arm,cortex-a8")) { + div = 2; + } else if (of_device_is_compatible(np, "arm,cortex-a9")) { + div = 1; + } else if (of_device_is_compatible(np, "arm,cortex-a7") || + of_device_is_compatible(np, "arm,cortex-a15")) { + div = 1; has_arch_timer = true; } } of_node_put(cpus); - if (!max_freq) + if (!max_freq || !div) return; - if (!has_arch_timer || !IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) { - if (is_a7_a8_a9) - shmobile_setup_delay_hz(max_freq, 1, 3); - else if (is_a15) - shmobile_setup_delay_hz(max_freq, 2, 4); - } + if (!has_arch_timer || !IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) + shmobile_setup_delay_hz(max_freq, 1, div); } |