Bootloader firmware expects the following traffic for
JUMP_TO_BOOTLOADER:

S Addr Wr [A] 0x0c [A] 0x01 [A] P

using ziirave_firm_write_byte() will result in

S Addr Wr [A] 0x0c [A] 0x01 [A] 0x01 [A] P

which happens to work because firmware will ignore any extra bytes and
expected magic value matches byte count sent by
i2c_smbus_write_block_data(). Fix this by converting the code to use
i2c_smbus_write_byte_data() instead.

Signed-off-by: Andrey Smirnov <andrew.smir...@gmail.com>
Cc: Chris Healy <cphe...@gmail.com>
Cc: Guenter Roeck <li...@roeck-us.net>
Cc: Rick Ramstetter <r...@anteaterllc.com>
Cc: linux-watch...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/watchdog/ziirave_wdt.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/ziirave_wdt.c b/drivers/watchdog/ziirave_wdt.c
index 0c150f3cf408..0185b9175cc0 100644
--- a/drivers/watchdog/ziirave_wdt.c
+++ b/drivers/watchdog/ziirave_wdt.c
@@ -72,6 +72,8 @@ static char *ziirave_reasons[] = {"power cycle", "hw 
watchdog", NULL, NULL,
 #define ZIIRAVE_CMD_JUMP_TO_BOOTLOADER         0x0c
 #define ZIIRAVE_CMD_DOWNLOAD_PACKET            0x0e
 
+#define ZIIRAVE_CMD_JUMP_TO_BOOTLOADER_MAGIC   1
+
 #define ZIIRAVE_FW_VERSION_FMT "02.%02u.%02u"
 #define ZIIRAVE_BL_VERSION_FMT "01.%02u.%02u"
 
@@ -376,8 +378,9 @@ static int ziirave_firm_upload(struct watchdog_device *wdd,
        const struct ihex_binrec *rec;
        int ret;
 
-       ret = ziirave_firm_write_byte(wdd, ZIIRAVE_CMD_JUMP_TO_BOOTLOADER, 1,
-                                     false);
+       ret = i2c_smbus_write_byte_data(client,
+                                       ZIIRAVE_CMD_JUMP_TO_BOOTLOADER,
+                                       ZIIRAVE_CMD_JUMP_TO_BOOTLOADER_MAGIC);
        if (ret) {
                dev_err(&client->dev, "Failed to jump to bootloader\n");
                return ret;
-- 
2.21.0

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