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Subject[PATCH RESEND 1/4] i2c: mpc: get MPC8xxx I2C clock prescaler before using it in calculations
Date
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 <asolokha@kb.kras.ru>
---
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 950a9d74f54d..6ad87555f71e 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",
--
2.15.1
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