Re: [PATCH v2 5/6] watchdog: Add Renesas RZ/N1 Watchdog driver

From: Jean-Jacques Hiblot
Date: Wed Feb 09 2022 - 13:22:16 EST

Hi Geert,

On 09/02/2022 09:28, Geert Uytterhoeven wrote:
Hi Jean-Jacques,

On Tue, Feb 8, 2022 at 7:35 PM Jean-Jacques Hiblot
<jjhiblot@xxxxxxxxxxxxxxx> wrote:
From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>

This is a driver for the standard WDT on the RZ/N1 devices. This WDT has
very limited timeout capabilities. However, it can reset the device.
To do so, the corresponding bits in the SysCtrl RSTEN register need to
be enabled. This is not done by this driver.

Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
Thanks for your patch!

--- /dev/null
+++ b/drivers/watchdog/rzn1_wdt.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Renesas RZ/N1 Watchdog timer.
+ * This is a 12-bit timer driver from a (62.5/16384) MHz clock. It can't even
+ * cope with 2 seconds.
+ *
+ * Copyright 2018 Renesas Electronics Europe Ltd.
+ *
+ * Derived from Ralink RT288x watchdog timer.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define DEFAULT_TIMEOUT 60
+
+#define RZN1_WDT_RETRIGGER 0x0
+#define RZN1_WDT_RETRIGGER_RELOAD_VAL 0
+#define RZN1_WDT_RETRIGGER_RELOAD_VAL_MASK 0xfff
+#define RZN1_WDT_RETRIGGER_PRESCALE BIT(12)
+#define RZN1_WDT_RETRIGGER_ENABLE BIT(13)
+#define RZN1_WDT_RETRIGGER_WDSI (0x2 << 14)
+
+#define RZN1_WDT_PRESCALER 16384
+#define RZN1_WDT_MAX 4095
+
+struct rzn1_watchdog {
+ struct watchdog_device wdt;
+ void __iomem *base;
+ unsigned long clk_rate;
+};
+
+#define to_rzn1_watchdog(_ptr) \
+ container_of(_ptr, struct rzn1_watchdog, wdt)
+
+static inline uint32_t get_max_heart_beat(uint32_t clk_rate)
unsigned long clk_rate

+{
+ return (RZN1_WDT_MAX * RZN1_WDT_PRESCALER) / (clk_rate / 1000);
Is clk_rate always a multiple of 1000? If not, you want to reorder
this to avoid losing precision.

The clock is 62.5 MHz, so dividing by 1000 doesn't cause a big precision loss.

I could use the 64bit division but it seemed less readable and the watchdog is

not used as a precise timer anyway.


+}
+static inline uint32_t compute_reload_value(uint32_t tick_ms, uint32_t clk)
unsigned long clk_rate

+{
+ return (tick_ms * (clk / 1000)) / RZN1_WDT_PRESCALER;
Likewise.

+}
+static int rzn1_wdt_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct rzn1_watchdog *wdt;
+ struct device_node *np = dev->of_node;
+ struct clk *clk;
+ int ret;
+ int irq;
+
+ wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt)
+ return -ENOMEM;
+
+ wdt->wdt = rzn1_wdt;
+ wdt->wdt.parent = dev;
+
+ wdt->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(wdt->base))
+ return PTR_ERR(wdt->base);
+
+ irq = platform_get_irq(pdev, 0);
+ if (irq < 0) {
+ dev_err(dev, "failed to get the irq\n");
No need to print a message, platform_get_irq() already does that.

+ return irq;
+ }
+
+ ret = devm_request_irq(dev, irq, rzn1_wdt_irq, 0,
+ np->name, wdt);
+ if (ret) {
+ dev_err(dev, "failed to request irq %d\n", irq);
+ return ret;
+ }
+
+ clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(clk)) {
+ dev_err(dev, "failed to get the clock\n");
+ return PTR_ERR(clk);
+ }
+
+ ret = clk_prepare_enable(clk);
+ if (ret) {
+ dev_err(dev, "failed to prepare/enable the clock\n");
+ return ret;
+ }
+
+ ret = devm_add_action_or_reset(dev, rzn1_wdt_clk_disable_unprepare,
+ clk);
+ if (ret) {
+ dev_err(dev, "failed to register clock unprepare callback\n");
+ clk_disable_unprepare(clk);
Please drop this, as devm_add_action_or_reset() calls the
action on failure.

+ return ret;
+ }
+
+ wdt->clk_rate = clk_get_rate(clk);
+ if (!wdt->clk_rate) {
+ dev_err(dev, "failed to get the clock rate\n");
+ return -EINVAL;
+ }
+
+ /*
+ * The period of the watchdog cannot be changed once set
+ * and is limited to a very short period.
+ * Configure it for a 1s period once and for all, and
+ * rely on the heart-beat provided by the watchdog core
+ * to make this usable by the user-space.
+ */
+ wdt->wdt.max_hw_heartbeat_ms = get_max_heart_beat(wdt->clk_rate);
+ if (wdt->wdt.max_hw_heartbeat_ms > 1000)
+ wdt->wdt.max_hw_heartbeat_ms = 1000;
+
+ wdt->wdt.timeout = DEFAULT_TIMEOUT;
+ ret = watchdog_init_timeout(&wdt->wdt, 0, dev);
+
+ return devm_watchdog_register_device(dev, &wdt->wdt);
+}
+
+
+static const struct of_device_id rzn1_wdt_match[] = {
+ { .compatible = "renesas,r9a06g032-wdt" },
No need to match on the soc-specific compatible value, as the
family-specific value should be present in the DTB, too.

+ { .compatible = "renesas,rzn1-wdt" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, rzn1_wdt_match);
Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds