watchdog: ziirave_wdt: Don't try to program readonly flash

Bootloader code will ignore any attempts to write data to any flash
area outside of [ZIIRAVE_FIRM_FLASH_MEMORY_START;
ZIIRAVE_FIRM_FLASH_MEMORY_END]. Firmware update code already have an
appropriate check to skip those areas when validating updated
firmware. Firmware programming code, OTOH, does not and will
needlessly send no-op I2C traffic. Add an appropriate check to
__ziirave_firm_write_pkt() so as to save all of that wasted effort.

While at it, normalize all of the address handling code to use full
32-bit address in units of bytes and convert it to an appropriate
value only in places where that is necessary.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Rick Ramstetter <rick@anteaterllc.com>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190812200906.31344-15-andrew.smirnov@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

diff --git a/drivers/watchdog/ziirave_wdt.c b/drivers/watchdog/ziirave_wdt.c
index f05095b08016de3023b21b6b17ff8499d402a4a8..a3cc936858adad2271d0b74271145c35efa7c8e2 100644 (file)
--- a/drivers/watchdog/ziirave_wdt.c
+++ b/drivers/watchdog/ziirave_wdt.c
@@ -51,8 +51,8 @@ static char *ziirave_reasons[] = {"power cycle", "hw watchdog", NULL, NULL,
 
 #define ZIIRAVE_FIRM_PKT_TOTAL_SIZE    20
 #define ZIIRAVE_FIRM_PKT_DATA_SIZE     16
-#define ZIIRAVE_FIRM_FLASH_MEMORY_START        0x1600
-#define ZIIRAVE_FIRM_FLASH_MEMORY_END  0x2bbf
+#define ZIIRAVE_FIRM_FLASH_MEMORY_START        (2 * 0x1600)
+#define ZIIRAVE_FIRM_FLASH_MEMORY_END  (2 * 0x2bbf)
 #define ZIIRAVE_FIRM_PAGE_SIZE         128
 
 /* Received and ready for next Download packet. */
@@ -195,12 +195,13 @@ static int ziirave_firm_wait_for_ack(struct watchdog_device *wdd)
        return ret == ZIIRAVE_FIRM_DOWNLOAD_ACK ? 0 : -EIO;
 }
 
-static int ziirave_firm_set_read_addr(struct watchdog_device *wdd, u16 addr)
+static int ziirave_firm_set_read_addr(struct watchdog_device *wdd, u32 addr)
 {
        struct i2c_client *client = to_i2c_client(wdd->parent);
+       const u16 addr16 = (u16)addr / 2;
        u8 address[2];
 
-       put_unaligned_le16(addr, address);
+       put_unaligned_le16(addr16, address);
 
        return i2c_smbus_write_block_data(client,
                                          ZIIRAVE_CMD_DOWNLOAD_SET_READ_ADDR,
@@ -234,6 +235,12 @@ static int ziirave_firm_write_byte(struct watchdog_device *wdd, u8 command,
                                             wait_for_ack);
 }
 
+static bool ziirave_firm_addr_readonly(u32 addr)
+{
+       return addr < ZIIRAVE_FIRM_FLASH_MEMORY_START ||
+              addr > ZIIRAVE_FIRM_FLASH_MEMORY_END;
+}
+
 /*
  * ziirave_firm_write_pkt() - Build and write a firmware packet
  *
@@ -261,6 +268,16 @@ static int __ziirave_firm_write_pkt(struct watchdog_device *wdd,
                return -EMSGSIZE;
        }
 
+       /*
+        * Ignore packets that are targeting program memory outisde of
+        * app partition, since they will be ignored by the
+        * bootloader. At the same time, we need to make sure we'll
+        * allow zero length packet that will be sent as the last step
+        * of firmware update
+        */
+       if (len && ziirave_firm_addr_readonly(addr))
+               return 0;
+
        /* Packet length */
        packet[0] = len;
        /* Packet address */
@@ -279,7 +296,7 @@ static int __ziirave_firm_write_pkt(struct watchdog_device *wdd,
        if (ret)
                dev_err(&client->dev,
                      "Failed to write firmware packet at address 0x%04x: %d\n",
-                     addr16, ret);
+                     addr, ret);
 
        return ret;
 }
@@ -315,14 +332,12 @@ static int ziirave_firm_verify(struct watchdog_device *wdd,
        const struct ihex_binrec *rec;
        int i, ret;
        u8 data[ZIIRAVE_FIRM_PKT_DATA_SIZE];
-       u16 addr;
 
        for (rec = (void *)fw->data; rec; rec = ihex_next_binrec(rec)) {
                const u16 len = be16_to_cpu(rec->len);
+               const u32 addr = be32_to_cpu(rec->addr);
 
-               addr = (be32_to_cpu(rec->addr) & 0xffff) >> 1;
-               if (addr < ZIIRAVE_FIRM_FLASH_MEMORY_START ||
-                   addr > ZIIRAVE_FIRM_FLASH_MEMORY_END)
+               if (ziirave_firm_addr_readonly(addr))
                        continue;
 
                ret = ziirave_firm_set_read_addr(wdd, addr);