[PATCH] i3c: master: dw-i3c-master: fix OD timing for first broadcast

[tze.yee.ng at altera.com]

From: Tze Yee Ng <tze.yee.ng at altera.com>

Implement ->set_speed() so the I3C core can switch open-drain timing for
the first broadcast address per spec: I3C_OPEN_DRAIN_SLOW_SPEED programs
tHIGH_INIT (200 ns) before RSTDAA, and I3C_OPEN_DRAIN_NORMAL_SPEED restores
normal OD timing afterward. Cache the normal OD register value during bus
init and use a separate od_hcnt for the slow path so SDR extended timing
remains derived from the normal PP hcnt.

Fixes I2C devices with spike filters not being detected on mixed buses.

Signed-off-by: Tze Yee Ng <tze.yee.ng at altera.com>
---
 drivers/i3c/master/dw-i3c-master.c | 53 ++++++++++++++++++++++++++++++
 drivers/i3c/master/dw-i3c-master.h |  1 +
 include/linux/i3c/master.h         |  1 +
 3 files changed, 55 insertions(+)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 655693a2187e..dbb801910b3d 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -592,6 +592,7 @@ static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
 	scl_timing = SCL_I3C_TIMING_HCNT(hcnt) | SCL_I3C_TIMING_LCNT(lcnt);
 	writel(scl_timing, master->regs + SCL_I3C_OD_TIMING);
 	master->i3c_od_timing = scl_timing;
+	master->i3c_od_timing_normal = scl_timing;
 
 	lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_SDR1_SCL_RATE) - hcnt;
 	scl_timing = SCL_EXT_LCNT_1(lcnt);
@@ -1480,6 +1481,57 @@ static irqreturn_t dw_i3c_master_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static int dw_i3c_master_set_speed(struct i3c_master_controller *m,
+				   enum i3c_open_drain_speed speed)
+{
+	struct dw_i3c_master *master = to_dw_i3c_master(m);
+	unsigned long core_rate, core_period;
+	u32 scl_timing;
+	u8 od_hcnt, lcnt;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(master->dev);
+	if (ret < 0) {
+		dev_err(master->dev,
+			"<%s> cannot resume i3c bus master, err: %d\n",
+			__func__, ret);
+		return ret;
+	}
+
+	switch (speed) {
+	case I3C_OPEN_DRAIN_SLOW_SPEED:
+		core_rate = clk_get_rate(master->core_clk);
+		if (!core_rate) {
+			ret = -EINVAL;
+			break;
+		}
+
+		core_period = DIV_ROUND_UP(1000000000, core_rate);
+		lcnt = SCL_I3C_TIMING_LCNT(master->i3c_od_timing_normal);
+		od_hcnt = max_t(u8, SCL_I3C_TIMING_CNT_MIN,
+				DIV_ROUND_UP(I3C_BUS_THIGH_INIT_OD_MIN_NS,
+					     core_period) - 1);
+		scl_timing = SCL_I3C_TIMING_HCNT(od_hcnt) |
+			     SCL_I3C_TIMING_LCNT(lcnt);
+		writel(scl_timing, master->regs + SCL_I3C_OD_TIMING);
+		master->i3c_od_timing = scl_timing;
+		break;
+
+	case I3C_OPEN_DRAIN_NORMAL_SPEED:
+		writel(master->i3c_od_timing_normal,
+		       master->regs + SCL_I3C_OD_TIMING);
+		master->i3c_od_timing = master->i3c_od_timing_normal;
+		break;
+
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	pm_runtime_put_autosuspend(master->dev);
+
+	return ret;
+}
+
 static int dw_i3c_master_set_dev_nack_retry(struct i3c_master_controller *m,
 					    unsigned long dev_nack_retry_cnt)
 {
@@ -1534,6 +1586,7 @@ static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
 	.recycle_ibi_slot = dw_i3c_master_recycle_ibi_slot,
 	.enable_hotjoin = dw_i3c_master_enable_hotjoin,
 	.disable_hotjoin = dw_i3c_master_disable_hotjoin,
+	.set_speed = dw_i3c_master_set_speed,
 	.set_dev_nack_retry = dw_i3c_master_set_dev_nack_retry,
 };
 
diff --git a/drivers/i3c/master/dw-i3c-master.h b/drivers/i3c/master/dw-i3c-master.h
index c5cb695c16ab..c814087a6f1f 100644
--- a/drivers/i3c/master/dw-i3c-master.h
+++ b/drivers/i3c/master/dw-i3c-master.h
@@ -46,6 +46,7 @@ struct dw_i3c_master {
 	u32 dev_addr;
 	u32 i3c_pp_timing;
 	u32 i3c_od_timing;
+	u32 i3c_od_timing_normal;
 	u32 ext_lcnt_timing;
 	u32 bus_free_timing;
 	u32 i2c_fm_timing;
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index 592b646f6134..c7d7448c4cd7 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -259,6 +259,7 @@ struct i3c_device {
 #define I3C_BUS_THIGH_MIXED_MAX_NS	41
 #define I3C_BUS_TIDLE_MIN_NS		200000
 #define I3C_BUS_TLOW_OD_MIN_NS		200
+#define I3C_BUS_THIGH_INIT_OD_MIN_NS	200
 
 /**
  * enum i3c_bus_mode - I3C bus mode
-- 
2.43.7