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watchdog: dw: RMW the control register

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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>
This commit is contained in:
Brian Norris 2018-03-09 19:46:06 -08:00 committed by Wim Van Sebroeck
parent 3c578cd4bc
commit a81abbb412
1 changed files with 15 additions and 8 deletions
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23
drivers/watchdog/dw_wdt.c
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@ -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 watchdog_device *wdd, unsigned int top_s)
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 watchdog_device *wdd,
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);