Commit 6d106139 authored Dec 07, 2017 by Arseny Solokha Committed by Wolfram Sang Jan 15, 2018

i2c: mpc: get MPC8xxx I2C clock prescaler before using it in calculations



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>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

parent aad550f9

drivers/i2c/busses/i2c-mpc.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -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",

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