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

[Frank Li]

On Wed, Jun 10, 2026 at 01:14:26AM -0700, tze.yee.ng at altera.com wrote:
> 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;
> +	}

	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(dev->dev, pm);
	if (PM_RUNTIME_ACQUIRE_ERR(&pm))
		return -ENXIO;

Use modem QCQUIRE macro

> +
> +	switch (speed) {
> +	case I3C_OPEN_DRAIN_SLOW_SPEED:
> +		core_rate = clk_get_rate(master->core_clk);
> +		if (!core_rate) {
> +			ret = -EINVAL;
> +			break;

you can return ret; here after use ACQUIRE macro.

Frank
> +		}
> +
> +		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
>