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clocksource/drivers/arm_arch_timer: validate arch_timer_rate 

Using an arch timer with a frequency of less than 1MHz can potentially
result in incorrect functionality in systems that assume a reasonable
rate of the arch timer of 1 to 50MHz, described as typical in the
architecture specification.

Therefore, warn if the arch timer rate is below 1MHz, which is
considered atypical and worth emphasizing.

Suggested-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ionela Voinescu 2020-03-05 09:06:27 +00:00 committed by Catalin Marinas
parent cd0ed03a89
commit c265861af2
1 changed files with 15 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/clocksource/arm_arch_timer.c
View File

@ -885,6 +885,17 @@ static int arch_timer_starting_cpu(unsigned int cpu)
return 0; return 0;
} }
static int validate_timer_rate(void)
{
if (!arch_timer_rate)
return -EINVAL;
/* Arch timer frequency < 1MHz can cause trouble */
WARN_ON(arch_timer_rate < 1000000);
return 0;
}
/* /*
* For historical reasons, when probing with DT we use whichever (non-zero) * For historical reasons, when probing with DT we use whichever (non-zero)
* rate was probed first, and don't verify that others match. If the first node * rate was probed first, and don't verify that others match. If the first node
@ -900,7 +911,7 @@ static void arch_timer_of_configure_rate(u32 rate, struct device_node *np)
arch_timer_rate = rate; arch_timer_rate = rate;
/* Check the timer frequency. */ /* Check the timer frequency. */
if (arch_timer_rate == 0) if (validate_timer_rate())
pr_warn("frequency not available\n"); pr_warn("frequency not available\n");
} }
@ -1594,9 +1605,10 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
* CNTFRQ value. This *must* be correct. * CNTFRQ value. This *must* be correct.
*/ */
arch_timer_rate = arch_timer_get_cntfrq(); arch_timer_rate = arch_timer_get_cntfrq();
if (!arch_timer_rate) { ret = validate_timer_rate();
if (ret) {
pr_err(FW_BUG "frequency not available.\n"); pr_err(FW_BUG "frequency not available.\n");
return -EINVAL; return ret;
} }
arch_timer_uses_ppi = arch_timer_select_ppi(); arch_timer_uses_ppi = arch_timer_select_ppi();