[PATCH 7/7] watchdog: imx93: add watchdog timer on imx93

From: Alice Guo (OSS)
Date: Tue Aug 16 2022 - 03:09:52 EST


From: Alice Guo <alice.guo@xxxxxxx>

The WDOG clocks are sourced from lpo_clk, and lpo_clk is the fixed
32KHz. TOVAL contains the 16-bit value used to set the timeout period of
the watchdog. When the timeout period exceeds 2 seconds, the value
written to the TOVAL register is larger than 16-bit can represent.
Enabling watchdog prescaler can solve this problem.

Two points need to be aware of:
1. watchdog prescaler enables a fixed 256 pre-scaling of watchdog
counter reference clock
2. reconfiguration takes about 55ms on imx93

Reviewed-by: Jacky Bai <ping.bai@xxxxxxx>
Signed-off-by: Alice Guo <alice.guo@xxxxxxx>
---
drivers/watchdog/imx7ulp_wdt.c | 33 ++++++++++++++++++++++++++++-----
1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
index 58508f69d933..4694aa4b8cfb 100644
--- a/drivers/watchdog/imx7ulp_wdt.c
+++ b/drivers/watchdog/imx7ulp_wdt.c
@@ -9,6 +9,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
+#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>
@@ -52,11 +53,17 @@ module_param(nowayout, bool, 0000);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

+struct imx_wdt_hw_feature {
+ bool prescaler_enable;
+ u32 wdog_clock_rate;
+};
+
struct imx7ulp_wdt_device {
struct watchdog_device wdd;
void __iomem *base;
struct clk *clk;
bool post_rcs_wait;
+ const struct imx_wdt_hw_feature *hw;
};

static int imx7ulp_wdt_wait_ulk(void __iomem *base)
@@ -179,7 +186,7 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
unsigned int timeout)
{
struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
- u32 toval = WDOG_CLOCK_RATE * timeout;
+ u32 toval = wdt->hw->wdog_clock_rate * timeout;
u32 val;
int ret;
u32 loop = RETRY_MAX;
@@ -276,6 +283,9 @@ static int imx7ulp_wdt_init(struct imx7ulp_wdt_device *wdt, unsigned int timeout
int ret;
u32 loop = RETRY_MAX;

+ if (wdt->hw->prescaler_enable)
+ val |= WDOG_CS_PRES;
+
do {
ret = _imx7ulp_wdt_init(wdt, timeout, val);
toval = readl(wdt->base + WDOG_TOVAL);
@@ -346,7 +356,9 @@ static int imx7ulp_wdt_probe(struct platform_device *pdev)
watchdog_stop_on_reboot(wdog);
watchdog_stop_on_unregister(wdog);
watchdog_set_drvdata(wdog, imx7ulp_wdt);
- ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * WDOG_CLOCK_RATE);
+
+ imx7ulp_wdt->hw = of_device_get_match_data(dev);
+ ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * imx7ulp_wdt->hw->wdog_clock_rate);
if (ret)
return ret;

@@ -368,7 +380,7 @@ static int __maybe_unused imx7ulp_wdt_suspend_noirq(struct device *dev)
static int __maybe_unused imx7ulp_wdt_resume_noirq(struct device *dev)
{
struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
- u32 timeout = imx7ulp_wdt->wdd.timeout * WDOG_CLOCK_RATE;
+ u32 timeout = imx7ulp_wdt->wdd.timeout * imx7ulp_wdt->hw->wdog_clock_rate;
int ret;

ret = clk_prepare_enable(imx7ulp_wdt->clk);
@@ -389,9 +401,20 @@ static const struct dev_pm_ops imx7ulp_wdt_pm_ops = {
imx7ulp_wdt_resume_noirq)
};

+static const struct imx_wdt_hw_feature imx7ulp_wdt_hw = {
+ .prescaler_enable = false,
+ .wdog_clock_rate = 1000,
+};
+
+static const struct imx_wdt_hw_feature imx93_wdt_hw = {
+ .prescaler_enable = true,
+ .wdog_clock_rate = 125,
+};
+
static const struct of_device_id imx7ulp_wdt_dt_ids[] = {
- { .compatible = "fsl,imx8ulp-wdt", },
- { .compatible = "fsl,imx7ulp-wdt", },
+ { .compatible = "fsl,imx8ulp-wdt", .data = &imx7ulp_wdt_hw, },
+ { .compatible = "fsl,imx7ulp-wdt", .data = &imx7ulp_wdt_hw, },
+ { .compatible = "fsl,imx93-wdt", .data = &imx93_wdt_hw, },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx7ulp_wdt_dt_ids);
--
2.17.1