[PATCH 1/4] i2c: mpc: get MPC8xxx I2C clock prescaler before using it in calculations

[Arseny Solokha]

Obtaining the actual I2C clock prescaler value in mpc_i2c_setup_8xxx() only
happens when the clock parameter is set to something other than
MPC_I2C_CLOCK_LEGACY. When the clock parameter is exactly
MPC_I2C_CLOCK_LEGACY, the prescaler parameter is used in arithmetic
division as provided by the caller, resulting in a division by zero
for the majority of processors supported by the module.

Avoid division by zero by obtaining the actual I2C clock prescaler
in mpc_i2c_setup_8xxx() unconditionally regardless of the passed clock
value.

Signed-off-by: Arseny Solokha 
---
 drivers/i2c/busses/i2c-mpc.c | 12 ++--
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 96caf378b1dc..bf0c86d41f1a 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -382,18 +382,18 @@ static int mpc_i2c_get_fdr_8xxx(struct device_node *node, 
u32 clock,
u32 divider;
int i;
 
-   if (clock == MPC_I2C_CLOCK_LEGACY) {
-   /* see below - default fdr = 0x1031 -> div = 16 * 3072 */
-   *real_clk = fsl_get_sys_freq() / prescaler / (16 * 3072);
-   return -EINVAL;
-   }
-
/* Determine proper divider value */
if (of_device_is_compatible(node, "fsl,mpc8544-i2c"))
prescaler = mpc_i2c_get_sec_cfg_8xxx() ? 3 : 2;
if (!prescaler)
prescaler = mpc_i2c_get_prescaler_8xxx();
 
+   if (clock == MPC_I2C_CLOCK_LEGACY) {
+   /* see below - default fdr = 0x1031 -> div = 16 * 3072 */
+   *real_clk = fsl_get_sys_freq() / prescaler / (16 * 3072);
+   return -EINVAL;
+   }
+
divider = fsl_get_sys_freq() / clock / prescaler;
 
pr_debug("I2C: src_clock=%d clock=%d divider=%d\n",
-- 
2.15.0

[PATCH 1/4] i2c: mpc: get MPC8xxx I2C clock prescaler before using it in calculations

[Arseny Solokha]

Obtaining the actual I2C clock prescaler value in mpc_i2c_setup_8xxx() only
happens when the clock parameter is set to something other than
MPC_I2C_CLOCK_LEGACY. When the clock parameter is exactly
MPC_I2C_CLOCK_LEGACY, the prescaler parameter is used in arithmetic
division as provided by the caller, resulting in a division by zero
for the majority of processors supported by the module.

Avoid division by zero by obtaining the actual I2C clock prescaler
in mpc_i2c_setup_8xxx() unconditionally regardless of the passed clock
value.

Signed-off-by: Arseny Solokha 
---
 drivers/i2c/busses/i2c-mpc.c | 12 ++--
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 96caf378b1dc..bf0c86d41f1a 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -382,18 +382,18 @@ static int mpc_i2c_get_fdr_8xxx(struct device_node *node, 
u32 clock,
u32 divider;
int i;
 
-   if (clock == MPC_I2C_CLOCK_LEGACY) {
-   /* see below - default fdr = 0x1031 -> div = 16 * 3072 */
-   *real_clk = fsl_get_sys_freq() / prescaler / (16 * 3072);
-   return -EINVAL;
-   }
-
/* Determine proper divider value */
if (of_device_is_compatible(node, "fsl,mpc8544-i2c"))
prescaler = mpc_i2c_get_sec_cfg_8xxx() ? 3 : 2;
if (!prescaler)
prescaler = mpc_i2c_get_prescaler_8xxx();
 
+   if (clock == MPC_I2C_CLOCK_LEGACY) {
+   /* see below - default fdr = 0x1031 -> div = 16 * 3072 */
+   *real_clk = fsl_get_sys_freq() / prescaler / (16 * 3072);
+   return -EINVAL;
+   }
+
divider = fsl_get_sys_freq() / clock / prescaler;
 
pr_debug("I2C: src_clock=%d clock=%d divider=%d\n",
-- 
2.15.0