[PATCH 4.16 171/272] watchdog: dw: RMW the control register

Greg Kroah-Hartman
2018-05-28T11:41:56Z

From: Brian Norris <briannorris@chromium.org>

[ Upstream commit a81abbb412341e9e3b2d42ed7d310cf71fbb84a8 ]

RK3399 has rst_pulse_length in CONTROL_REG[4:2], determining the length
of pulse to issue for system reset. We shouldn't clobber this value,
because that might make the system reset ineffective. On RK3399, we're
seeing that a value of 000b (meaning 2 cycles) yields an unreliable
(partial?) reset, and so we only fully reset after the watchdog fires a
second time. If we retain the system default (010b, or 8 clock cycles),
then the watchdog reset is much more reliable.

Read-modify-write retains the system value and improves reset
reliability.

It seems we were intentionally clobbering the response mode previously,
to ensure we performed a system reset (we don't support an interrupt
notification), so retain that explicitly.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/watchdog/dw_wdt.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -34,6 +34,7 @@

#define WDOG_CONTROL_REG_OFFSET 0x00
#define WDOG_CONTROL_REG_WDT_EN_MASK 0x01
+#define WDOG_CONTROL_REG_RESP_MODE_MASK 0x02
#define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04
#define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT 4
#define WDOG_CURRENT_COUNT_REG_OFFSET 0x08
@@ -121,14 +122,23 @@ static int dw_wdt_set_timeout(struct wat
return 0;
}

+static void dw_wdt_arm_system_reset(struct dw_wdt *dw_wdt)
+{
+ u32 val = readl(dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
+
+ /* Disable interrupt mode; always perform system reset. */
+ val &= ~WDOG_CONTROL_REG_RESP_MODE_MASK;
+ /* Enable watchdog. */
+ val |= WDOG_CONTROL_REG_WDT_EN_MASK;
+ writel(val, dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
+}
+
static int dw_wdt_start(struct watchdog_device *wdd)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);

dw_wdt_set_timeout(wdd, wdd->timeout);
-
- writel(WDOG_CONTROL_REG_WDT_EN_MASK,
- dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
+ dw_wdt_arm_system_reset(dw_wdt);

return 0;
}
@@ -152,16 +162,13 @@ static int dw_wdt_restart(struct watchdo
unsigned long action, void *data)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);
- u32 val;

writel(0, dw_wdt->regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
- val = readl(dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
- if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
+ if (dw_wdt_is_enabled(dw_wdt))
writel(WDOG_COUNTER_RESTART_KICK_VALUE,
dw_wdt->regs + WDOG_COUNTER_RESTART_REG_OFFSET);
else
- writel(WDOG_CONTROL_REG_WDT_EN_MASK,
- dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
+ dw_wdt_arm_system_reset(dw_wdt);

/* wait for reset to assert... */
mdelay(500);