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Date:   Mon, 09 Jan 2023 10:39:32 +0000
Message-ID: <86ilhgng9n.wl-maz@kernel.org>
From:   Marc Zyngier <maz@kernel.org>
To:     Yogesh Lal <quic_ylal@quicinc.com>
Cc:     <mark.rutland@arm.com>, <daniel.lezcano@linaro.org>,
        <tglx@linutronix.de>, <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>
Subject: Re: ERRATUM_858921 is broken on 5.15 kernel
In-Reply-To: <9aafa9d9-70f8-67de-df43-e2fb282a4a67@quicinc.com>
References: <ca4679a0-7f29-65f4-54b9-c575248192f1@quicinc.com>
        <86sfgpnjsg.wl-maz@kernel.org>
        <9aafa9d9-70f8-67de-df43-e2fb282a4a67@quicinc.com>
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On Mon, 09 Jan 2023 06:52:20 +0000,
Yogesh Lal <quic_ylal@quicinc.com> wrote:
> 
> tested it on affected h/w but looks like sched_clock is still pointing
> to !arch_timer_counter_has_wa() function calls,
> may be due to sched_clock_register will register once during non
> errata impacted core booting.

Ah, of course. We register the function itself instead of an
indirection. Please try this on top of the previous patch.

Thanks,

	M.

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index a7cf0a2c86d3..8232c86b9e7c 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -217,7 +217,12 @@ static notrace u64 arch_counter_get_cntvct(void)
  * to exist on arm64. arm doesn't use this before DT is probed so even
  * if we don't have the cp15 accessors we won't have a problem.
  */
-u64 (*arch_timer_read_counter)(void) __ro_after_init = arch_counter_get_cntvct;
+static u64 (*__arch_timer_read_counter)(void) __ro_after_init = arch_counter_get_cntvct;
+
+u64 arch_timer_read_counter(void)
+{
+	return __arch_timer_read_counter();
+}
 EXPORT_SYMBOL_GPL(arch_timer_read_counter);
 
 static u64 arch_counter_read(struct clocksource *cs)
@@ -595,7 +600,7 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
 
 	if (wa->read_cntvct_el0 || wa->read_cntpct_el0) {
 		atomic_set(&timer_unstable_counter_workaround_in_use, 1);
-		arch_timer_read_counter = arch_counter_get_read_fn();
+		__arch_timer_read_counter = arch_counter_get_read_fn();
 	}
 
 	/*
@@ -1103,10 +1108,10 @@ static void __init arch_counter_register(unsigned type)
 
 	/* Register the CP15 based counter if we have one */
 	if (type & ARCH_TIMER_TYPE_CP15) {
-		arch_timer_read_counter = arch_counter_get_read_fn();
+		__arch_timer_read_counter = arch_counter_get_read_fn();
 		clocksource_counter.vdso_clock_mode = vdso_default;
 	} else {
-		arch_timer_read_counter = arch_counter_get_cntvct_mem;
+		__arch_timer_read_counter = arch_counter_get_cntvct_mem;
 	}
 
 	width = arch_counter_get_width();
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index e3c3816d19ba..3ac297a756e8 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -89,7 +89,7 @@ struct arch_timer_mem {
 #ifdef CONFIG_ARM_ARCH_TIMER
 
 extern u32 arch_timer_get_rate(void);
-extern u64 (*arch_timer_read_counter)(void);
+extern u64 arch_timer_read_counter(void);
 extern struct arch_timer_kvm_info *arch_timer_get_kvm_info(void);
 extern bool arch_timer_evtstrm_available(void);
 

-- 
Without deviation from the norm, progress is not possible.