linux-kernel - [PATCH 2/2] i3c: master: svc: use slow speed for first broadcast address

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Message-Id: <20240806064851.2425797-2-carlos.song@nxp.com>
Date: Tue,  6 Aug 2024 14:48:51 +0800
From: carlos.song@....com
To: alexandre.belloni@...tlin.com,
	frank.li@....com,
	miquel.raynal@...tlin.com,
	conor.culhane@...vaco.com
Cc: linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-imx@....com
Subject: [PATCH 2/2] i3c: master: svc: use slow speed for first broadcast address

From: Carlos Song <carlos.song@....com>

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@....com>
---
 drivers/i3c/master/svc-i3c-master.c | 51 +++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 0a68fd1b81d4..4cdce25c5cf7 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -212,6 +212,7 @@ struct svc_i3c_master {
 	} ibi;
 	struct mutex lock;
 	int enabled_events;
+	u32 mctrl_config;
 };
 
 /**
@@ -529,6 +530,54 @@ 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);
+	unsigned long fclk_rate;
+	u32 ppbaud, odbaud, odhpp, mconfig;
+	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 +660,7 @@ 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 +1695,7 @@ 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)
-- 
2.34.1