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clocksource/drivers/arm_arch_timer: Work around broken CVAL implementations

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The Applied Micro XGene-1 SoC has a busted implementation of the
CVAL register: it looks like it is based on TVAL instead of the
other way around. The net effect of this implementation blunder
is that the maximum deadline you can program in the timer is
32bit wide.

Use a MIDR check to notice the broken CPU, and reduce the width
of the timer to 32bit.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211017124225.3018098-10-maz@kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
This commit is contained in:
Marc Zyngier 2021-10-17 13:42:17 +01:00 committed by Daniel Lezcano
parent 30aa08da35
commit 012f188504
1 changed files with 27 additions and 1 deletions
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28
drivers/clocksource/arm_arch_timer.c
View file

@ -780,9 +780,32 @@ static int arch_timer_set_next_event_phys_mem(unsigned long evt,
return 0;
}
static u64 __arch_timer_check_delta(void)
{
#ifdef CONFIG_ARM64
const struct midr_range broken_cval_midrs[] = {
/*
* XGene-1 implements CVAL in terms of TVAL, meaning
* that the maximum timer range is 32bit. Shame on them.
*/
MIDR_ALL_VERSIONS(MIDR_CPU_MODEL(ARM_CPU_IMP_APM,
APM_CPU_PART_POTENZA)),
{},
};
if (is_midr_in_range_list(read_cpuid_id(), broken_cval_midrs)) {
pr_warn_once("Broken CNTx_CVAL_EL1, limiting width to 32bits");
return CLOCKSOURCE_MASK(32);
}
#endif
return CLOCKSOURCE_MASK(56);
}
static void __arch_timer_setup(unsigned type,
struct clock_event_device *clk)
{
u64 max_delta;
clk->features = CLOCK_EVT_FEAT_ONESHOT;
if (type == ARCH_TIMER_TYPE_CP15) {
@ -814,6 +837,7 @@ static void __arch_timer_setup(unsigned type,
}
clk->set_next_event = sne;
max_delta = __arch_timer_check_delta();
} else {
clk->features |= CLOCK_EVT_FEAT_DYNIRQ;
clk->name = "arch_mem_timer";
@ -830,11 +854,13 @@ static void __arch_timer_setup(unsigned type,
clk->set_next_event =
arch_timer_set_next_event_phys_mem;
}
max_delta = CLOCKSOURCE_MASK(56);
}
clk->set_state_shutdown(clk);
clockevents_config_and_register(clk, arch_timer_rate, 0xf, CLOCKSOURCE_MASK(56));
clockevents_config_and_register(clk, arch_timer_rate, 0xf, max_delta);
}
static void arch_timer_evtstrm_enable(int divider)