From 0b46b8a718c6e90910a1b1b0fe797be3c167e186 Mon Sep 17 00:00:00 2001 From: Sonny Rao Date: Sun, 23 Nov 2014 23:02:44 -0800 Subject: clocksource: arch_timer: Fix code to use physical timers when requested This is a bug fix for using physical arch timers when the arch_timer_use_virtual boolean is false. It restores the arch_counter_get_cntpct() function after removal in 0d651e4e "clocksource: arch_timer: use virtual counters" We need this on certain ARMv7 systems which are architected like this: * The firmware doesn't know and doesn't care about hypervisor mode and we don't want to add the complexity of hypervisor there. * The firmware isn't involved in SMP bringup or resume. * The ARCH timer come up with an uninitialized offset between the virtual and physical counters. Each core gets a different random offset. * The device boots in "Secure SVC" mode. * Nothing has touched the reset value of CNTHCTL.PL1PCEN or CNTHCTL.PL1PCTEN (both default to 1 at reset) One example of such as system is RK3288 where it is much simpler to use the physical counter since there's nobody managing the offset and each time a core goes down and comes back up it will get reinitialized to some other random value. Fixes: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters") Cc: stable@vger.kernel.org Signed-off-by: Sonny Rao Acked-by: Catalin Marinas Acked-by: Daniel Lezcano Signed-off-by: Olof Johansson --- drivers/clocksource/arm_arch_timer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 2133f9d59d06..55256e4fb641 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -462,7 +462,10 @@ static void __init arch_counter_register(unsigned type) /* Register the CP15 based counter if we have one */ if (type & ARCH_CP15_TIMER) { - arch_timer_read_counter = arch_counter_get_cntvct; + if (arch_timer_use_virtual) + arch_timer_read_counter = arch_counter_get_cntvct; + else + arch_timer_read_counter = arch_counter_get_cntpct; } else { arch_timer_read_counter = arch_counter_get_cntvct_mem; -- cgit v1.2.3 From 65b5732d241b8b39e07653794eefffd0d8028cbb Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Wed, 8 Oct 2014 00:33:47 -0700 Subject: clocksource: arch_timer: Allow the device tree to specify uninitialized timer registers Some 32-bit (ARMv7) systems are architected like this: * The firmware doesn't know and doesn't care about hypervisor mode and we don't want to add the complexity of hypervisor there. * The firmware isn't involved in SMP bringup or resume. * The ARCH timer come up with an uninitialized offset (CNTVOFF) between the virtual and physical counters. Each core gets a different random offset. * The device boots in "Secure SVC" mode. * Nothing has touched the reset value of CNTHCTL.PL1PCEN or CNTHCTL.PL1PCTEN (both default to 1 at reset) On systems like the above, it doesn't make sense to use the virtual counter. There's nobody managing the offset and each time a core goes down and comes back up it will get reinitialized to some other random value. This adds an optional property which can inform the kernel of this situation, and firmware is free to remove the property if it is going to initialize the CNTVOFF registers when each CPU comes out of reset. Currently, the best course of action in this case is to use the physical timer, which is why it is important that CNTHCTL hasn't been changed from its reset value and it's a reasonable assumption given that the firmware has never entered HYP mode. Note that it's been said that on ARMv8 systems the firmware and kernel really can't be architected as described above. That means using the physical timer like this really only makes sense for ARMv7 systems. Signed-off-by: Doug Anderson Signed-off-by: Sonny Rao Reviewed-by: Mark Rutland Acked-by: Daniel Lezcano Acked-by: Catalin Marinas Signed-off-by: Olof Johansson --- drivers/clocksource/arm_arch_timer.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'drivers') diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 55256e4fb641..6967cb026b9e 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -704,6 +704,14 @@ static void __init arch_timer_init(struct device_node *np) arch_timer_ppi[i] = irq_of_parse_and_map(np, i); arch_timer_detect_rate(NULL, np); + /* + * If we cannot rely on firmware initializing the timer registers then + * we should use the physical timers instead. + */ + if (IS_ENABLED(CONFIG_ARM) && + of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) + arch_timer_use_virtual = false; + /* * If HYP mode is available, we know that the physical timer * has been configured to be accessible from PL1. Use it, so -- cgit v1.2.3