i2c: Blackfin TWI: make sure we don't end up with a CLKDIV=0

Make sure we don't end up with an invalid CLKDIV=0 in case someone
specifies 20kHz SCL or less (5 * 1024 / 20 = 0x100).

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
[ben-linux@fluff.org: shortened subject line]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

2 files changed, 9 insertions, 4 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index f1c6ca7e285..c8460fa9cfa 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -298,7 +298,7 @@ config I2C_BLACKFIN_TWI
 config I2C_BLACKFIN_TWI_CLK_KHZ
         int "Blackfin TWI I2C clock (kHz)"
         depends on I2C_BLACKFIN_TWI
-        range 10 400
+        range 21 400
         default 50
         help
           The unit of the TWI clock is kHz.
diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
index fc548b3d002..77cafb6ba92 100644
--- a/drivers/i2c/busses/i2c-bfin-twi.c
+++ b/drivers/i2c/busses/i2c-bfin-twi.c
@@ -614,6 +614,7 @@ static int i2c_bfin_twi_probe(struct platform_device *pdev)
         struct i2c_adapter *p_adap;
         struct resource *res;
         int rc;
+        unsigned int clkhilow;
 
         iface = kzalloc(sizeof(struct bfin_twi_iface), GFP_KERNEL);
         if (!iface) {
@@ -675,10 +676,14 @@ static int i2c_bfin_twi_probe(struct platform_device *pdev)
         /* Set TWI internal clock as 10MHz */
         write_CONTROL(iface, ((get_sclk() / 1024 / 1024 + 5) / 10) & 0x7F);
 
+        /*
+         * We will not end up with a CLKDIV=0 because no one will specify
+         * 20kHz SCL or less in Kconfig now. (5 * 1024 / 20 = 0x100)
+         */
+        clkhilow = 5 * 1024 / CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ;
+
         /* Set Twi interface clock as specified */
-        write_CLKDIV(iface, ((5*1024 / CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ)
-                        << 8) | ((5*1024 / CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ)
-                        & 0xFF));
+        write_CLKDIV(iface, (clkhilow << 8) | clkhilow);
 
         /* Enable TWI */
         write_CONTROL(iface, read_CONTROL(iface) | TWI_ENA);