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SubjectRe: [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for multiple erratum detection methods
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Hi Dann,

On 24/03/17 17:48, dann frazier wrote:
> On Mon, Mar 20, 2017 at 11:48 AM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>> We're currently stuck with DT when it comes to handling errata, which
>> is pretty restrictive. In order to make things more flexible, let's
>> introduce an infrastructure that could support alternative discovery
>> methods. No change in functionality.
>>
>> Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> arch/arm64/include/asm/arch_timer.h | 7 +++-
>> drivers/clocksource/arm_arch_timer.c | 80 +++++++++++++++++++++++++++++++-----
>> 2 files changed, 75 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
>> index b4b34004a21e..5cd964e90d11 100644
>> --- a/arch/arm64/include/asm/arch_timer.h
>> +++ b/arch/arm64/include/asm/arch_timer.h
>> @@ -37,9 +37,14 @@ extern struct static_key_false arch_timer_read_ool_enabled;
>> #define needs_unstable_timer_counter_workaround() false
>> #endif
>>
>> +enum arch_timer_erratum_match_type {
>> + ate_match_dt,
>> +};
>>
>> struct arch_timer_erratum_workaround {
>> - const char *id; /* Indicate the Erratum ID */
>> + enum arch_timer_erratum_match_type match_type;
>> + const void *id;
>> + const char *desc;
>> u32 (*read_cntp_tval_el0)(void);
>> u32 (*read_cntv_tval_el0)(void);
>> u64 (*read_cntvct_el0)(void);
>> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
>> index 7a8a4117f123..6a0f0e161a0f 100644
>> --- a/drivers/clocksource/arm_arch_timer.c
>> +++ b/drivers/clocksource/arm_arch_timer.c
>> @@ -182,7 +182,9 @@ EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
>> static const struct arch_timer_erratum_workaround ool_workarounds[] = {
>> #ifdef CONFIG_FSL_ERRATUM_A008585
>> {
>> + .match_type = ate_match_dt,
>> .id = "fsl,erratum-a008585",
>> + .desc = "Freescale erratum a005858",
>> .read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
>> .read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
>> .read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
>> @@ -190,13 +192,78 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
>> #endif
>> #ifdef CONFIG_HISILICON_ERRATUM_161010101
>> {
>> + .match_type = ate_match_dt,
>> .id = "hisilicon,erratum-161010101",
>> + .desc = "HiSilicon erratum 161010101",
>> .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
>> .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
>> .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
>> },
>> #endif
>> };
>> +
>> +typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
>> + const void *);
>> +
>> +static
>> +bool arch_timer_check_dt_erratum(const struct arch_timer_erratum_workaround *wa,
>> + const void *arg)
>> +{
>> + const struct device_node *np = arg;
>> +
>> + return of_property_read_bool(np, wa->id);
>> +}
>> +
>> +static const struct arch_timer_erratum_workaround *
>> +arch_timer_iterate_errata(enum arch_timer_erratum_match_type type,
>> + ate_match_fn_t match_fn,
>> + void *arg)
>> +{
>> + int i;
>> +
>> + for (i = 0; i < ARRAY_SIZE(ool_workarounds); i++) {
>> + if (ool_workarounds[i].match_type != type)
>> + continue;
>> +
>> + if (match_fn(&ool_workarounds[i], arg))
>> + return &ool_workarounds[i];
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static
>> +void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa)
>> +{
>> + timer_unstable_counter_workaround = wa;
>> + static_branch_enable(&arch_timer_read_ool_enabled);
>> +}
>> +
>> +static void arch_timer_check_ool_workaround(enum arch_timer_erratum_match_type type,
>> + void *arg)
>> +{
>> + const struct arch_timer_erratum_workaround *wa;
>> + ate_match_fn_t match_fn = NULL;
>> +
>> + if (static_branch_unlikely(&arch_timer_read_ool_enabled))
>> + return;
>> +
>> + switch (type) {
>> + case ate_match_dt:
>> + match_fn = arch_timer_check_dt_erratum;
>> + break;
>
> hey Marc,
> Would it make sense to have a default case here that warns &
> returns? That wouldn't get hit by this series as-is, but might avoid a
> NULL callback in the future.

Sure, I can add that in the next version of this series. I would have
hoped that GCC would warn you if you don't handle all the values of an
enum, but it doesn't hurt to be cautious.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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