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Message-Id: <20250515-vt8500-timer-updates-v3-3-2197a1b062bd@gmail.com>
Date: Thu, 15 May 2025 21:55:28 +0300
From: Alexey Charkov <alchark@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Wim Van Sebroeck <wim@...ux-watchdog.org>,
Guenter Roeck <linux@...ck-us.net>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, linux-watchdog@...r.kernel.org,
Alexey Charkov <alchark@...il.com>
Subject: [PATCH v3 3/4] clocksource/drivers/timer-vt8500: Prepare for
watchdog functionality
VIA/WonderMedia system timer can generate a watchdog reset when its
clocksource counter matches the value in the match register 0 and
watchdog function is enabled. For this to work, obvously the clock event
device must use a different match register (1~3) and respective interrupt.
Check if at least two interrupts are provided by the device tree, then use
match register 1 for system clock events and reserve match register 0 for
the watchdog. Instantiate a platform device for the watchdog and give it
access to the MMIO registers base of the timer through platform data.
Signed-off-by: Alexey Charkov <alchark@...il.com>
---
drivers/clocksource/timer-vt8500.c | 68 +++++++++++++++++++++++++++++++++++---
1 file changed, 63 insertions(+), 5 deletions(-)
diff --git a/drivers/clocksource/timer-vt8500.c b/drivers/clocksource/timer-vt8500.c
index 9f28f30dcaf83ab4e9c89952175b0d4c75bd6b40..122cc046140d5e9edff20ff41a49b4e62064dd40 100644
--- a/drivers/clocksource/timer-vt8500.c
+++ b/drivers/clocksource/timer-vt8500.c
@@ -21,6 +21,8 @@
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
#define VT8500_TIMER_OFFSET 0x0100
#define VT8500_TIMER_HZ 3000000
@@ -55,6 +57,9 @@
#define MIN_OSCR_DELTA 16
static void __iomem *regbase;
+static unsigned int sys_timer_ch; /* which match register to use
+ * for the system timer
+ */
static u64 vt8500_timer_read(struct clocksource *cs)
{
@@ -81,15 +86,15 @@ static int vt8500_timer_set_next_event(unsigned long cycles,
int loops = msecs_to_loops(10);
u64 alarm = clocksource.read(&clocksource) + cycles;
- while (readl(regbase + TIMER_ACC_STS_REG) & TIMER_ACC_WR_MATCH(0)
+ while (readl(regbase + TIMER_ACC_STS_REG) & TIMER_ACC_WR_MATCH(sys_timer_ch)
&& --loops)
cpu_relax();
- writel((unsigned long)alarm, regbase + TIMER_MATCH_REG(0));
+ writel((unsigned long)alarm, regbase + TIMER_MATCH_REG(sys_timer_ch));
if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
return -ETIME;
- writel(TIMER_INT_EN_MATCH(0), regbase + TIMER_INT_EN_REG);
+ writel(TIMER_INT_EN_MATCH(sys_timer_ch), regbase + TIMER_INT_EN_REG);
return 0;
}
@@ -131,7 +136,9 @@ static int __init vt8500_timer_init(struct device_node *np)
return -ENXIO;
}
- timer_irq = irq_of_parse_and_map(np, 0);
+ sys_timer_ch = of_irq_count(np) > 1 ? 1 : 0;
+
+ timer_irq = irq_of_parse_and_map(np, sys_timer_ch);
if (!timer_irq) {
pr_err("%s: Missing irq description in Device Tree\n",
__func__);
@@ -140,7 +147,7 @@ static int __init vt8500_timer_init(struct device_node *np)
writel(TIMER_CTRL_ENABLE, regbase + TIMER_CTRL_REG);
writel(TIMER_STATUS_CLEARALL, regbase + TIMER_STATUS_REG);
- writel(~0, regbase + TIMER_MATCH_REG(0));
+ writel(~0, regbase + TIMER_MATCH_REG(sys_timer_ch));
ret = clocksource_register_hz(&clocksource, VT8500_TIMER_HZ);
if (ret) {
@@ -166,4 +173,55 @@ static int __init vt8500_timer_init(struct device_node *np)
return 0;
}
+/*
+ * This probe gets called after the timer is already up and running. This will create
+ * the watchdog device as a child since the registers are shared.
+ */
+static int vt8500_timer_probe(struct platform_device *pdev)
+{
+ struct platform_device *vt8500_watchdog_device;
+ struct device *dev = &pdev->dev;
+ int ret;
+
+ if (!sys_timer_ch) {
+ dev_info(dev, "Not enabling watchdog: only one irq was given");
+ return 0;
+ }
+
+ if (!regbase)
+ return dev_err_probe(dev, -ENOMEM,
+ "Timer not initialized, cannot create watchdog");
+
+ vt8500_watchdog_device = platform_device_alloc("vt8500-wdt", -1);
+ if (!vt8500_watchdog_device)
+ return dev_err_probe(dev, -ENOMEM,
+ "Failed to allocate vt8500-wdt");
+
+ /* Pass the base address as platform data and nothing else */
+ vt8500_watchdog_device->dev.platform_data = regbase;
+ vt8500_watchdog_device->dev.parent = dev;
+
+ ret = platform_device_add(vt8500_watchdog_device);
+ if (ret)
+ platform_device_put(vt8500_watchdog_device);
+
+ return ret;
+}
+
+static const struct of_device_id vt8500_timer_of_match[] = {
+ { .compatible = "via,vt8500-timer", },
+ {},
+};
+
+static struct platform_driver vt8500_timer_driver = {
+ .probe = vt8500_timer_probe,
+ .driver = {
+ .name = "vt8500-timer",
+ .of_match_table = vt8500_timer_of_match,
+ .suppress_bind_attrs = true,
+ },
+};
+
+builtin_platform_driver(vt8500_timer_driver);
+
TIMER_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);
--
2.49.0
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