Re: [PATCH V4 1/2] i3c: master: support to adjust first broadcast address speed

[Frank Li]

On Thu, Sep 05, 2024 at 03:45:56PM +0800, Carlos Song wrote:
> 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@xxxxxxx>
> Reviewed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

Alexandre Belloni:

	I have not seen these in patch work
	https://patchwork.kernel.org/project/linux-i3c/list/

	Any thing wrong. These two patches is critial for some boards.
Could you please take care it?

best regards
Frank Li

> ---
> Change for V4:
> - No change. Send this patch with svc-i3c-master.c fix patch.
> Change for V3:
> - Modify comments from Miquel's suggestion
> Chnage for V2:
> - Fix set_speed description from Frank's comment
> ---
>  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..2a1ed05d5782 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 sending the first
> + *				broadcast address. The first broadcast address at this speed
> + *				will be visible to all devices on the I3C bus. I3C devices
> + *				working in I2C mode will turn off their spike filter when
> + *				switching into I3C mode.
> + * @I3C_OPEN_DRAIN_NORMAL_SPEED: Normal open-drain speed in 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.
>   */
>  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
>