| Message ID | 1452537674-20006-2-git-send-email-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | a8dabbeef60c2c1f1865b06f0455f99fc24c0719 |
| Delegated to: | Simon Horman |
| Headers | show |
On Mon, Jan 11, 2016 at 07:41:12PM +0100, Geert Uytterhoeven wrote: > 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> > --- > Backporting note: older kernels need modifications in all calls to > shmobile_setup_delay() or shmobile_setup_delay_hz(). Thanks, I have queued this up for v4.6. -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm/mach-shmobile/timer.c b/arch/arm/mach-shmobile/timer.c index c17d4d3881ffc45e..d61014a52b43e205 100644 --- a/arch/arm/mach-shmobile/timer.c +++ b/arch/arm/mach-shmobile/timer.c @@ -38,8 +38,7 @@ 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; @@ -53,27 +52,22 @@ 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); }
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> --- Backporting note: older kernels need modifications in all calls to shmobile_setup_delay() or shmobile_setup_delay_hz(). --- arch/arm/mach-shmobile/timer.c | 28 +++++++++++----------------- 1 file changed, 11 insertions(+), 17 deletions(-)