linux-kernel - [PATCH v2 16/22] watchdog: ziirave_wdt: Fix JUMP_TO

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Date:   Mon, 12 Aug 2019 13:09:00 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     linux-watchdog@...r.kernel.org
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Chris Healy <cphealy@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Rick Ramstetter <rick@...eaterllc.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 16/22] watchdog: ziirave_wdt: Fix JUMP_TO_BOOTLOADER payload

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.smirnov@...il.com>
Cc: Chris Healy <cphealy@...il.com>
Cc: Guenter Roeck <linux@...ck-us.net>
Cc: Rick Ramstetter <rick@...eaterllc.com>
Cc: linux-watchdog@...r.kernel.org
Cc: linux-kernel@...r.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