[PATCH 1/5] phy: cpcap-usb: Prevent line glitches from triggering sysrq

[Ivaylo Dimitrov]

From: Tony Lindgren <tony at atomide.com>

We can get random sysrq events on switching from USB to debug serial
port mode unless is temporarily disable sysrq for the mode changes.

Signed-off-by: Tony Lindgren <tony at atomide.com>
---
 drivers/phy/motorola/phy-cpcap-usb.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/phy/motorola/phy-cpcap-usb.c b/drivers/phy/motorola/phy-cpcap-usb.c
index 7cb020dd3423..c6cc8fce6940 100644
--- a/drivers/phy/motorola/phy-cpcap-usb.c
+++ b/drivers/phy/motorola/phy-cpcap-usb.c
@@ -20,6 +20,7 @@
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/sysrq.h>
 
 #include <linux/gpio/consumer.h>
 #include <linux/mfd/motorola-cpcap.h>
@@ -413,7 +414,12 @@ static int cpcap_usb_gpio_set_mode(struct cpcap_phy_ddata *ddata,
 
 static int cpcap_usb_set_uart_mode(struct cpcap_phy_ddata *ddata)
 {
-	int error;
+	int sysrq, error;
+
+	/* Disable sysrq to prevent random sysrq events on line glitches */
+	sysrq = sysrq_mask();
+	if (sysrq & 1)
+		sysrq_toggle_support(sysrq & ~1);
 
 	/* Disable lines to prevent glitches from waking up mdm6600 */
 	error = cpcap_usb_gpio_set_mode(ddata, CPCAP_UNKNOWN_DISABLED);
@@ -448,6 +454,9 @@ static int cpcap_usb_set_uart_mode(struct cpcap_phy_ddata *ddata)
 	if (error)
 		goto out_err;
 
+	if (sysrq & 1)
+		sysrq_toggle_support(sysrq);
+
 	return 0;
 
 out_err:
-- 
2.25.1