diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c index d04a3a14461433..12743934e8e285 100644 --- a/drivers/i2c/busses/i2c-designware-master.c +++ b/drivers/i2c/busses/i2c-designware-master.c @@ -38,20 +38,32 @@ static void i2c_dw_configure_fifo_master(struct dw_i2c_dev *dev) regmap_write(dev->map, DW_IC_CON, dev->master_cfg); } -static u16 clock_calc(struct dw_i2c_dev *dev, bool want_high) +static u32 linear_interpolate(u32 x, u32 x1, u32 x2, u32 y1, u32 y2) { - struct i2c_timings *t = &dev->timings; - u32 wanted_speed = dev->wanted_bus_speed ?: t->bus_freq_hz; - u32 clk_khz = i2c_dw_clk_rate(dev); - u32 extra_ns = want_high ? t->scl_fall_ns : t->scl_rise_ns; - u32 extra_cycles = (u32)((u64)clk_khz * extra_ns / 1000000); - u32 period = ((u64)clk_khz * 1000 + wanted_speed - 1) / wanted_speed; - u32 cycles = (period + want_high)/2 - extra_cycles; + return ((x - x1) * y2 + (x2 - x) * y1) / (x2 - x1); +} - if (cycles > 0xffff) - cycles = 0xffff; +static u16 u16_clamp(u32 v) +{ + return (u16)min(v, 0xffff); +} - return (u16)cycles; +static void clock_calc(struct dw_i2c_dev *dev, u32 *hcnt, u32 *lcnt) +{ + struct i2c_timings *t = &dev->timings; + u32 wanted_khz = (dev->wanted_bus_speed ?: t->bus_freq_hz)/1000; + u32 clk_khz = i2c_dw_clk_rate(dev); + u32 min_high_ns = (wanted_khz <= 100) ? 4000 : + (wanted_khz <= 400) ? + linear_interpolate(wanted_khz, 100, 400, 4000, 600) : + linear_interpolate(wanted_khz, 400, 1000, 600, 260); + u32 high_cycles = (u32)(((u64)clk_khz * min_high_ns + 999999) / 1000000) + 1; + u32 extra_high_cycles = (u32)((u64)clk_khz * t->scl_fall_ns / 1000000); + u32 extra_low_cycles = (u32)((u64)clk_khz * t->scl_rise_ns / 1000000); + u32 period = ((u64)clk_khz + wanted_khz - 1) / wanted_khz; + + *hcnt = u16_clamp(high_cycles - extra_high_cycles); + *lcnt = u16_clamp(period - high_cycles - extra_low_cycles); } static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev) @@ -77,8 +89,7 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev) sda_falling_time = t->sda_fall_ns ?: 300; /* ns */ scl_falling_time = t->scl_fall_ns ?: 300; /* ns */ - hcnt = clock_calc(dev, true); - lcnt = clock_calc(dev, false); + clock_calc(dev, &hcnt, &lcnt); /* Calculate SCL timing parameters for standard mode if not set */ if (!dev->ss_hcnt || !dev->ss_lcnt) {