i2c: designware: Use SCL rise and fall times in DT

Calculate the HCNT and LCNT values for all modes using the rise and
fall times of SCL, the aim being a 50/50 mark/space ratio.

Signed-off-by: Phil Elwell <[email protected]>

Author: pelwell

drivers/i2c/busses/i2c-designware-master.c

@@ -38,13 +38,30 @@ 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)
+{
+	struct i2c_timings *t = &dev->timings;
+	u32 wanted_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;
+
+	if (cycles > 0xffff)
+		cycles = 0xffff;
+
+	return (u16)cycles;
+}
+
 static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
 {
 	unsigned int comp_param1;
 	u32 sda_falling_time, scl_falling_time;
 	struct i2c_timings *t = &dev->timings;
 	const char *fp_str = "";
 	u32 ic_clk;
+	u32 hcnt, lcnt;
 	int ret;
 
 	ret = i2c_dw_acquire_lock(dev);
@@ -60,6 +77,9 @@ 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);
+
 	/* Calculate SCL timing parameters for standard mode if not set */
 	if (!dev->ss_hcnt || !dev->ss_lcnt) {
 		ic_clk = i2c_dw_clk_rate(dev);
@@ -75,6 +95,8 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
 					scl_falling_time,
 					0);	/* No offset */
 	}
+	dev->ss_hcnt = hcnt;
+	dev->ss_lcnt = lcnt;
 	dev_dbg(dev->dev, "Standard Mode HCNT:LCNT = %d:%d\n",
 		dev->ss_hcnt, dev->ss_lcnt);
 
@@ -125,6 +147,8 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
 					scl_falling_time,
 					0);	/* No offset */
 	}
+	dev->fs_hcnt = hcnt;
+	dev->fs_lcnt = lcnt;
 	dev_dbg(dev->dev, "Fast Mode%s HCNT:LCNT = %d:%d\n",
 		fp_str, dev->fs_hcnt, dev->fs_lcnt);
 
@@ -153,6 +177,8 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
 						scl_falling_time,
 						0);	/* No offset */
 		}
+		dev->hs_hcnt = hcnt;
+		dev->hs_lcnt = lcnt;
 		dev_dbg(dev->dev, "High Speed Mode HCNT:LCNT = %d:%d\n",
 			dev->hs_hcnt, dev->hs_lcnt);
 	}