i3c: master: svc: use slow speed for first broadcast address

I3C controller should support adjusting open drain timing for the first
broadcast address to make I3C device working as a i2c device can see slow
broadcast address to close its Spike Filter to change working at i3c mode.
Signed-off-by: Carlos Song <carlos.song@nxp.com>
Reviewed-by: Frank Li <frank.li@nxp.com>
Link: https://lore.kernel.org/r/20240910051626.4052552-2-carlos.song@nxp.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/i3c/master/svc-i3c-master.c

@@ -182,6 +182,7 @@ struct svc_i3c_regs_save {
  * @ibi.lock: IBI lock
  * @lock: Transfer lock, protect between IBI work thread and callbacks from master
  * @enabled_events: Bit masks for enable events (IBI, HotJoin).
+ * @mctrl_config: Configuration value in SVC_I3C_MCTRL for setting speed back.
  */
 struct svc_i3c_master {
 	struct i3c_master_controller base;
@@ -212,6 +213,7 @@ struct svc_i3c_master {
 	} ibi;
 	struct mutex lock;
 	int enabled_events;
+	u32 mctrl_config;
 };
 
 /**
@@ -529,6 +531,54 @@ static irqreturn_t svc_i3c_master_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static int svc_i3c_master_set_speed(struct i3c_master_controller *m,
+				     enum i3c_open_drain_speed speed)
+{
+	struct svc_i3c_master *master = to_svc_i3c_master(m);
+	struct i3c_bus *bus = i3c_master_get_bus(&master->base);
+	u32 ppbaud, odbaud, odhpp, mconfig;
+	unsigned long fclk_rate;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(master->dev);
+	if (ret < 0) {
+		dev_err(master->dev, "<%s> Cannot get runtime PM.\n", __func__);
+		return ret;
+	}
+
+	switch (speed) {
+	case I3C_OPEN_DRAIN_SLOW_SPEED:
+		fclk_rate = clk_get_rate(master->fclk);
+		if (!fclk_rate) {
+			ret = -EINVAL;
+			goto rpm_out;
+		}
+		/*
+		 * Set 50% duty-cycle I2C speed to I3C OPEN-DRAIN mode, so the first
+		 * broadcast address is visible to all I2C/I3C devices on the I3C bus.
+		 * I3C device working as a I2C device will turn off its 50ns Spike
+		 * Filter to change to I3C mode.
+		 */
+		mconfig = master->mctrl_config;
+		ppbaud = FIELD_GET(GENMASK(11, 8), mconfig);
+		odhpp = 0;
+		odbaud = DIV_ROUND_UP(fclk_rate, bus->scl_rate.i2c * (2 + 2 * ppbaud)) - 1;
+		mconfig &= ~GENMASK(24, 16);
+		mconfig |= SVC_I3C_MCONFIG_ODBAUD(odbaud) | SVC_I3C_MCONFIG_ODHPP(odhpp);
+		writel(mconfig, master->regs + SVC_I3C_MCONFIG);
+		break;
+	case I3C_OPEN_DRAIN_NORMAL_SPEED:
+		writel(master->mctrl_config, master->regs + SVC_I3C_MCONFIG);
+		break;
+	}
+
+rpm_out:
+	pm_runtime_mark_last_busy(master->dev);
+	pm_runtime_put_autosuspend(master->dev);
+
+	return ret;
+}
+
 static int svc_i3c_master_bus_init(struct i3c_master_controller *m)
 {
 	struct svc_i3c_master *master = to_svc_i3c_master(m);
@@ -611,6 +661,7 @@ static int svc_i3c_master_bus_init(struct i3c_master_controller *m)
 	      SVC_I3C_MCONFIG_I2CBAUD(i2cbaud);
 	writel(reg, master->regs + SVC_I3C_MCONFIG);
 
+	master->mctrl_config = reg;
 	/* Master core's registration */
 	ret = i3c_master_get_free_addr(m, 0);
 	if (ret < 0)
@@ -1645,6 +1696,7 @@ static const struct i3c_master_controller_ops svc_i3c_master_ops = {
 	.disable_ibi = svc_i3c_master_disable_ibi,
 	.enable_hotjoin = svc_i3c_master_enable_hotjoin,
 	.disable_hotjoin = svc_i3c_master_disable_hotjoin,
+	.set_speed = svc_i3c_master_set_speed,
 };
 
 static int svc_i3c_master_prepare_clks(struct svc_i3c_master *master)