[PATCH v2 08/18] arm64: arch_timer: Add erratum handler for CPU-specific capability

[Marc Zyngier]

Should we ever have a workaround for an erratum that is detected using
a capability and affecting a particular CPU, it'd be nice to have
a way to probe them directly.

Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
---
 arch/arm64/include/asm/arch_timer.h  |  1 +
 drivers/clocksource/arm_arch_timer.c | 28 ++++++++++++++++++++++++----
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/arch_timer.h 
b/arch/arm64/include/asm/arch_timer.h
index 48bd730d568f..e5325299aa6d 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -40,6 +40,7 @@ extern struct static_key_false arch_timer_read_ool_enabled;
 enum arch_timer_erratum_match_type {
        ate_match_dt,
        ate_match_global_cap_id,
+       ate_match_local_cap_id,
 };
 
 struct arch_timer_erratum_workaround {
diff --git a/drivers/clocksource/arm_arch_timer.c 
b/drivers/clocksource/arm_arch_timer.c
index a0b1108a4a24..5069cb3d4326 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -221,6 +221,13 @@ bool arch_timer_check_global_cap_erratum(const struct 
arch_timer_erratum_workaro
        return cpus_have_cap((uintptr_t)wa->id);
 }
 
+static
+bool arch_timer_check_local_cap_erratum(const struct 
arch_timer_erratum_workaround *wa,
+                                       const void *arg)
+{
+       return this_cpu_has_cap((uintptr_t)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,
@@ -251,9 +258,7 @@ static void arch_timer_check_ool_workaround(enum 
arch_timer_erratum_match_type t
 {
        const struct arch_timer_erratum_workaround *wa;
        ate_match_fn_t match_fn = NULL;
-
-       if (static_branch_unlikely(&arch_timer_read_ool_enabled))
-               return;
+       bool local = false;
 
        switch (type) {
        case ate_match_dt:
@@ -262,14 +267,27 @@ static void arch_timer_check_ool_workaround(enum 
arch_timer_erratum_match_type t
        case ate_match_global_cap_id:
                match_fn = arch_timer_check_global_cap_erratum;
                break;
+       case ate_match_local_cap_id:
+               match_fn = arch_timer_check_local_cap_erratum;
+               local = true;
+               break;
        }
 
        wa = arch_timer_iterate_errata(type, match_fn, arg);
        if (!wa)
                return;
 
+       if (static_branch_unlikely(&arch_timer_read_ool_enabled)) {
+               if (wa != timer_unstable_counter_workaround)
+                       pr_warn("Can't enable workaround for %s (clashes with 
%s\n)",
+                               wa->desc,
+                               timer_unstable_counter_workaround->desc);
+               return;
+       }
+
        arch_timer_enable_workaround(wa);
-       pr_info("Enabling global workaround for %s\n", wa->desc);
+       pr_info("Enabling %s workaround for %s\n",
+               local ? "local" : "global", wa->desc);
 }
 
 #else
@@ -529,6 +547,8 @@ static void __arch_timer_setup(unsigned type,
                        BUG();
                }
 
+               arch_timer_check_ool_workaround(ate_match_local_cap_id, NULL);
+
                erratum_workaround_set_sne(clk);
        } else {
                clk->features |= CLOCK_EVT_FEAT_DYNIRQ;
-- 
2.11.0