Cadence watchdog HW supports prescaler values of
8, 64, 512 and 4096.
Add support to select prescaler values of 8 and 64 for lower
input clock frequencies.
Prescaler value is selected to keep timeout resolution of 1 second.
For clock frequencies below 32kHz, 1 second resolution does
no longer hold, thereby returning an error.
Signed-off-by: Tomas Melin <tomas.melin@xxxxxxxxxxx>
---
drivers/watchdog/cadence_wdt.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
index 4657800d9d8e..39109b5721c1 100644
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -33,16 +33,17 @@
#define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
/* Clock prescaler value and selection */
+#define CDNS_WDT_PRESCALE_8 8
#define CDNS_WDT_PRESCALE_64 64
#define CDNS_WDT_PRESCALE_512 512
#define CDNS_WDT_PRESCALE_4096 4096
+#define CDNS_WDT_PRESCALE_SELECT_8 0
#define CDNS_WDT_PRESCALE_SELECT_64 1
#define CDNS_WDT_PRESCALE_SELECT_512 2
#define CDNS_WDT_PRESCALE_SELECT_4096 3
-/* Input clock frequency */
-#define CDNS_WDT_CLK_10MHZ 10000000
-#define CDNS_WDT_CLK_75MHZ 75000000
+/* Base input clock frequency */
+#define CDNS_WDT_CLK_32KHZ 32768
/* Counter maximum value */
#define CDNS_WDT_COUNTER_MAX 0xFFF
@@ -304,7 +305,16 @@ static int cdns_wdt_probe(struct platform_device *pdev)
}
clock_f = clk_get_rate(wdt->clk);
- if (clock_f <= CDNS_WDT_CLK_75MHZ) {
+ if (clock_f < CDNS_WDT_CLK_32KHZ) {
+ dev_err(&pdev->dev, "cannot find suitable clock prescaler\n");
+ return -ERANGE;
+ } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_8) {
+ wdt->prescaler = CDNS_WDT_PRESCALE_8;
+ wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_8;
+ } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_64) {
+ wdt->prescaler = CDNS_WDT_PRESCALE_64;
+ wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_64;
+ } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_512) {
wdt->prescaler = CDNS_WDT_PRESCALE_512;
wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
} else {
--
2.17.2
