linux-kernel - Re: [PATCH 1/2] i3c: master: support to adjust first broadcast address speed

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Message-ID: <ZrJII9soS8sG2roT@lizhi-Precision-Tower-5810>
Date: Tue, 6 Aug 2024 11:58:27 -0400
From: Frank Li <Frank.li@....com>
To: carlos.song@....com
Cc: alexandre.belloni@...tlin.com, miquel.raynal@...tlin.com,
	conor.culhane@...vaco.com, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
	linux-imx@....com
Subject: Re: [PATCH 1/2] i3c: master: support to adjust first broadcast
 address speed

On Tue, Aug 06, 2024 at 02:48:50PM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
>
> According to I3C spec 6.2 Timing Specification, the Open Drain High Period
> of SCL Clock timing for first broadcast address should be adjusted to 200ns
> at least. I3C device working as i2c device will see the broadcast to close
> its Spike Filter then change to work at I3C mode. After that I3C open drain
> SCL high level should be adjusted back.
>
> Signed-off-by: Carlos Song <carlos.song@....com>

A small comments below

Reviewed-by: Frank Li <Frank.Li@....com>

> ---
>  drivers/i3c/master.c       | 12 ++++++++++++
>  include/linux/i3c/master.h | 16 ++++++++++++++++
>  2 files changed, 28 insertions(+)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index 7028f03c2c42..6f3eb710a75d 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -1868,6 +1868,12 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
>  		goto err_bus_cleanup;
>  	}
>
> +	if (master->ops->set_speed) {
> +		ret = master->ops->set_speed(master, I3C_OPEN_DRAIN_SLOW_SPEED);
> +		if (ret)
> +			goto err_bus_cleanup;
> +	}
> +
>  	/*
>  	 * Reset all dynamic address that may have been assigned before
>  	 * (assigned by the bootloader for example).
> @@ -1876,6 +1882,12 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
>  	if (ret && ret != I3C_ERROR_M2)
>  		goto err_bus_cleanup;
>
> +	if (master->ops->set_speed) {
> +		master->ops->set_speed(master, I3C_OPEN_DRAIN_NORMAL_SPEED);
> +		if (ret)
> +			goto err_bus_cleanup;
> +	}
> +
>  	/* Disable all slave events before starting DAA. */
>  	ret = i3c_master_disec_locked(master, I3C_BROADCAST_ADDR,
>  				      I3C_CCC_EVENT_SIR | I3C_CCC_EVENT_MR |
> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> index 074f632868d9..02e4f47f9d01 100644
> --- a/include/linux/i3c/master.h
> +++ b/include/linux/i3c/master.h
> @@ -277,6 +277,20 @@ enum i3c_bus_mode {
>  	I3C_BUS_MODE_MIXED_SLOW,
>  };
>
> +/**
> + * enum i3c_open_drain_speed - I3C open drain speed
> + * @I3C_OPEN_DRAIN_SLOW_SPEED: Slow open drain speed for First Broadcast Address.
> + *				First Broadcast Address in this speed 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 work in I3C mode.
> + * @I3C_OPEN_DRAIN_NORMAL_SPEED: Normal open drain speed configured according to
> + *				I3C bus mode.
> + */
> +enum i3c_open_drain_speed {
> +	I3C_OPEN_DRAIN_SLOW_SPEED,
> +	I3C_OPEN_DRAIN_NORMAL_SPEED,
> +};
> +
>  /**
>   * enum i3c_addr_slot_status - I3C address slot status
>   * @I3C_ADDR_SLOT_FREE: address is free
> @@ -436,6 +450,7 @@ struct i3c_bus {
>   *		      NULL.
>   * @enable_hotjoin: enable hot join event detect.
>   * @disable_hotjoin: disable hot join event detect.
> + * @set_speed: adjust I3C open drain mode timing.
		adjust I3C bus speed, which is generally used for reduced
		the speed for first broardcast address.
>   */
>  struct i3c_master_controller_ops {
>  	int (*bus_init)(struct i3c_master_controller *master);
> @@ -464,6 +479,7 @@ struct i3c_master_controller_ops {
>  				 struct i3c_ibi_slot *slot);
>  	int (*enable_hotjoin)(struct i3c_master_controller *master);
>  	int (*disable_hotjoin)(struct i3c_master_controller *master);
> +	int (*set_speed)(struct i3c_master_controller *master, enum i3c_open_drain_speed speed);
>  };
>
>  /**
> --
> 2.34.1
>