Using the information presented by GTDT to initialize the arch
timer (not memory-mapped).

Originally-by: Amit Daniel Kachhap [off-list ref]
Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Hanjun Guo <redacted>
---
arch/arm64/kernel/time.c             |   7 ++
drivers/clocksource/arm_arch_timer.c | 132
++++++++++++++++++++++++++++-------
include/linux/clocksource.h          |   6 ++
3 files changed, 118 insertions(+), 27 deletions(-)

diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
index 1a7125c..42f9195 100644
--- a/arch/arm64/kernel/time.c
+++ b/arch/arm64/kernel/time.c

@@ -35,6 +35,7 @@

#include <linux/delay.h>
#include <linux/clocksource.h>
#include <linux/clk-provider.h>
+#include <linux/acpi.h>

#include <clocksource/arm_arch_timer.h>

@@ -72,6 +73,12 @@ void __init time_init(void)

	tick_setup_hrtimer_broadcast();

+	/*
+	 * Since ACPI or FDT will only one be available in the system,
+	 * we can use acpi_generic_timer_init() here safely
+	 */
+	acpi_generic_timer_init();
+
	arch_timer_rate = arch_timer_get_rate();
	if (!arch_timer_rate)
		panic("Unable to initialise architected timer.\n");

diff --git a/drivers/clocksource/arm_arch_timer.c

b/drivers/clocksource/arm_arch_timer.c
index 6a79fc4..612f2a0 100644

--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c

@@ -21,6 +21,7 @@

#include <linux/io.h>
#include <linux/slab.h>
#include <linux/sched_clock.h>
+#include <linux/acpi.h>

#include <asm/arch_timer.h>
#include <asm/virt.h>

@@ -370,8 +371,12 @@ arch_timer_detect_rate(void __iomem *cntbase, struct

device_node *np)
	if (arch_timer_rate)
		return;

-	/* Try to determine the frequency from the device tree or CNTFRQ */
-	if (of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) {
+	/*
+	 * Try to determine the frequency from the device tree or CNTFRQ,
+	 * if ACPI is enabled, get the frequency from CNTFRQ ONLY.
+	 */
+	if (!acpi_disabled ||
+	    of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) {
		if (cntbase)
			arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);
		else

@@ -690,28 +695,8 @@ static void __init arch_timer_common_init(void)

	arch_timer_arch_init();
}

-static void __init arch_timer_init(struct device_node *np)
+static void __init arch_timer_init(void)
{
-	int i;
-
-	if (arch_timers_present & ARCH_CP15_TIMER) {
-		pr_warn("arch_timer: multiple nodes in dt, skipping\n");
-		return;
-	}
-
-	arch_timers_present |= ARCH_CP15_TIMER;
-	for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
-		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
-	arch_timer_detect_rate(NULL, np);
-
-	/*
-	 * If we cannot rely on firmware initializing the timer registers then
-	 * we should use the physical timers instead.
-	 */
-	if (IS_ENABLED(CONFIG_ARM) &&
-	    of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
-			arch_timer_use_virtual = false;
-
	/*
	 * If HYP mode is available, we know that the physical timer
	 * has been configured to be accessible from PL1. Use it, so

@@ -730,13 +715,39 @@ static void __init arch_timer_init(struct

device_node *np)
		}
	}

-	arch_timer_c3stop = !of_property_read_bool(np, "always-on");
-
	arch_timer_register();
	arch_timer_common_init();
}
-CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer",
arch_timer_init);
-CLOCKSOURCE_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer",
arch_timer_init);
+
+static void __init arch_timer_of_init(struct device_node *np)
+{
+	int i;
+
+	if (arch_timers_present & ARCH_CP15_TIMER) {
+		pr_warn("arch_timer: multiple nodes in dt, skipping\n");
+		return;
+	}
+
+	arch_timers_present |= ARCH_CP15_TIMER;
+	for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
+		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
+
+	arch_timer_detect_rate(NULL, np);
+
+	arch_timer_c3stop = !of_property_read_bool(np, "always-on");
+
+	/*
+	 * If we cannot rely on firmware initializing the timer registers then
+	 * we should use the physical timers instead.
+	 */
+	if (IS_ENABLED(CONFIG_ARM) &&
+	    of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
+			arch_timer_use_virtual = false;
+
+	arch_timer_init();
+}
+CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer",
arch_timer_of_init);
+CLOCKSOURCE_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer",
arch_timer_of_init);