Re: [PATCH v2 1/2] i3c: master: support to adjust first broadcast address speed

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi carlos.song@nxp.com,

carlos.song@nxp.com wrote on Wed,  7 Aug 2024 14:13:05 +0800:

> From: Carlos Song <carlos.song@nxp.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@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
> - Fix set_speed description from Frank's comment
> ---
>  drivers/i3c/master.c       | 12 ++++++++++++
>  include/linux/i3c/master.h | 18 ++++++++++++++++++
>  2 files changed, 30 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..b8daf09a9a4a 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.

A few minor style comments:

open-drain

...for sending the first broadcast address.

> + *				First Broadcast Address in this speed is visible to all I2C/I3C

The first broadcast address at this speed will be visible to all 

> + *				devices on the I3C bus. I3C device working as a I2C device will

... I3C devices working in I2C mode will

> + *				turn off its 50ns Spike Filter to change to work in I3C mode.

					their     spike filter when
					switching into I3C mode.

> + * @I3C_OPEN_DRAIN_NORMAL_SPEED: Normal open drain speed configured according to

open-drain

> + *				I3C bus mode.

I'm sorry, can you rephrase "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 +450,9 @@ struct i3c_bus {
>   *		      NULL.
>   * @enable_hotjoin: enable hot join event detect.
>   * @disable_hotjoin: disable hot join event detect.
> + * @set_speed: adjust I3C bus speed, which is generally used for reducing the speed
> + *		for first broardcast address.
> + *
>   */
>  struct i3c_master_controller_ops {
>  	int (*bus_init)(struct i3c_master_controller *master);
> @@ -464,6 +481,7 @@ 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);
>  };
>  
>  /**

Otherwise lgtm.

Thanks,
Miquèl

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