[PATCH v2 20/22] watchdog: ziirave_wdt: Fix DOWNLOAD_START payload

[Andrey Smirnov]

Bootloader firmware expects the following traffic for DOWNLOAD_END:

S Addr Wr [A] 0x10 [A] P

using ziirave_firm_write_byte() will result in

S Addr Wr [A] 0x10 [A] 0x01 [A] 0x01 [A] P

which happens to work because firmware will ignore any extra bytes
sent. Fix this by converting the code to use i2c_smbus_write_byte()
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 | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/watchdog/ziirave_wdt.c b/drivers/watchdog/ziirave_wdt.c
index 681f65349779..ed69fa82e09c 100644
--- a/drivers/watchdog/ziirave_wdt.c
+++ b/drivers/watchdog/ziirave_wdt.c
@@ -217,13 +217,6 @@ static int ziirave_firm_write_block_data(struct 
watchdog_device *wdd,
        return ret;
 }
 
-static int ziirave_firm_write_byte(struct watchdog_device *wdd, u8 command,
-                                  u8 byte, bool wait_for_ack)
-{
-       return ziirave_firm_write_block_data(wdd, command, 1, &byte,
-                                            wait_for_ack);
-}
-
 static bool ziirave_firm_addr_readonly(u32 addr)
 {
        return addr < ZIIRAVE_FIRM_FLASH_MEMORY_START ||
@@ -375,12 +368,18 @@ static int ziirave_firm_upload(struct watchdog_device 
*wdd,
 
        msleep(500);
 
-       ret = ziirave_firm_write_byte(wdd, ZIIRAVE_CMD_DOWNLOAD_START, 1, true);
+       ret = i2c_smbus_write_byte(client, ZIIRAVE_CMD_DOWNLOAD_START);
        if (ret) {
                dev_err(&client->dev, "Failed to start download\n");
                return ret;
        }
 
+       ret = ziirave_firm_read_ack(wdd);
+       if (ret) {
+               dev_err(&client->dev, "No ACK for start download\n");
+               return ret;
+       }
+
        msleep(500);
 
        for (rec = (void *)fw->data; rec; rec = ihex_next_binrec(rec)) {
-- 
2.21.0