[PATCH] watchdog: mpc8xx_wdt: Allow selection of watchdog mode through environment

[Christophe Leroy <christophe.leroy@c-s.fr>]

From: Charles Frey <charles.frey@c-s.fr>

The mpc8xx watchdog can work either in 'reset mode' or 'NMI mode'.
The selection can be done at startup only.
It is desirable to select the mode without rebuilding U-boot.
It is also desirable to disable the watchdog without rebuilding.

At watchdog startup, check environment variable 'watchdog_mode'.
If it is 'off', the watchdog is not started. If it is 'nmi',
the watchdog is started in NMI mode. Otherwise, it is started
in reset mode which is the default mode.

Signed-off-by: Charles Frey <charles.frey@c-s.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 drivers/watchdog/mpc8xx_wdt.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/mpc8xx_wdt.c b/drivers/watchdog/mpc8xx_wdt.c
index 675b62d8b3..8a7a4c5bc6 100644
--- a/drivers/watchdog/mpc8xx_wdt.c
+++ b/drivers/watchdog/mpc8xx_wdt.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <env.h>
 #include <dm.h>
 #include <wdt.h>
 #include <mpc8xx.h>
@@ -21,8 +22,15 @@ static void hw_watchdog_reset(void)
 static int mpc8xx_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
 {
 	immap_t __iomem *immap = (immap_t __iomem *)CONFIG_SYS_IMMR;
+	u32 val = CONFIG_SYS_SYPCR;
+	const char *mode = env_get("watchdog_mode");
 
-	out_be32(&immap->im_siu_conf.sc_sypcr, CONFIG_SYS_SYPCR);
+	if (strcmp(mode, "off") == 0)
+		val = val & ~(SYPCR_SWE | SYPCR_SWRI);
+	else if (strcmp(mode, "nmi") == 0)
+		val = (val & ~SYPCR_SWRI) | SYPCR_SWE;
+
+	out_be32(&immap->im_siu_conf.sc_sypcr, val);
 
 	if (!(in_be32(&immap->im_siu_conf.sc_sypcr) & SYPCR_SWE))
 		return -EBUSY;
-- 
2.25.0