Re: [PATCH 2/5] i2c: Add STM32F4 I2C driver

Hi Maxime,

quoted

quoted

+static void stm32f4_i2c_set_speed_mode(struct stm32f4_i2c_dev *i2c_dev)
+{
+       struct stm32f4_i2c_timings *t = &i2c_timings[i2c_dev->speed];
+       u32 ccr, val, clk_rate;
+
+       ccr = readl_relaxed(i2c_dev->base + STM32F4_I2C_CCR);
+       ccr &= ~(STM32F4_I2C_CCR_FS | STM32F4_I2C_CCR_DUTY |
+                STM32F4_I2C_CCR_CCR_MASK);
+
+       clk_rate = clk_get_rate(i2c_dev->clk);
+
+       switch (i2c_dev->speed) {
+       case STM32F4_I2C_SPEED_STANDARD:
+               val = clk_rate / t->rate * 2;
+               if (val < STM32F4_I2C_MIN_CCR)
+                       ccr |= STM32F4_I2C_CCR_CCR(STM32F4_I2C_MIN_CCR);
+               else
+                       ccr |= STM32F4_I2C_CCR_CCR(val);
+               break;
+       case STM32F4_I2C_SPEED_FAST:
+               ccr |= STM32F4_I2C_CCR_FS;
+               if (t->duty) {
+                       ccr |= STM32F4_I2C_CCR_DUTY;
+                       ccr |= STM32F4_I2C_CCR_CCR(clk_rate / t->rate * 25);
+               } else {
+                       ccr |= STM32F4_I2C_CCR_CCR(clk_rate / t->rate * 3);
+               }

Is it really useful since duty seems to always be 0?

Agree, I will rework it by directly set duty at 0 in the register.

Contrary to what I wrote previously, the duty has to be set for FAST
Mode to reach 400khz.
So, I am going to keep the timing struct and set duty to 1 for FAST mode