[PATCH v2] i3c: dw: reduce do_daa time if there's no client

[Alexandre Belloni]

Hi Jisheng,

On 14/08/2026 12:20:15+0800, Jisheng Zhang wrote:
> dw_i3c_master_daa() derives the number of newly assigned dynamic
> addresses from cmd->rx_len, the ISR sets it to the number of address
> slots ENTDAA left unassigned. It starts out as zero, which already
> means "every address was assigned", so a timed out transfer leaves
> that value in place and it gets used as a result.
> 
> If there's no client connected, the addr assign cmd times out, then
> the driver calls i3c_master_add_i3c_dev_locked() to add devices that
> are not there, each costing about 1s, thus adds non necessary boot
> time up to (maxdev * 1)s.
> 
> Start from maxdevs instead: no address is assigned before ENTDAA runs,
> and make newdevs as 0 if the existing rx_len >= maxdevs.
> 
> Signed-off-by: Jisheng Zhang <jszhang at kernel.org>
> ---
> 
> since v1:
>  - use another method to remove the non-necessary calling of
>    i3c_master_add_i3c_dev_locked() if there's no client
>  - update commit msg
> 
>  drivers/i3c/master/dw-i3c-master.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 

You'd have to rebase this one on i3c/next as it doesn't apply cleanly
anymore.

> diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
> index 1053cfb05c05..883b542c7bfc 100644
> --- a/drivers/i3c/master/dw-i3c-master.c
> +++ b/drivers/i3c/master/dw-i3c-master.c
> @@ -876,6 +876,7 @@ static int dw_i3c_master_daa(struct i3c_master_controller *m)
>  		goto rpm_out;
>  	}
>  	cmd = &xfer->cmds[0];
> +	cmd->rx_len = master->maxdevs;
>  	cmd->cmd_hi = COMMAND_PORT_TRANSFER_ARG;
>  	cmd->cmd_lo = COMMAND_PORT_DEV_COUNT(master->maxdevs - pos) |
>  		      COMMAND_PORT_DEV_INDEX(pos) |
> @@ -888,7 +889,10 @@ static int dw_i3c_master_daa(struct i3c_master_controller *m)
>  	if (!wait_for_completion_timeout(&xfer->comp, XFER_TIMEOUT))
>  		dw_i3c_master_dequeue_xfer(master, xfer);
>  
> -	newdevs = GENMASK(master->maxdevs - cmd->rx_len - 1, 0);
> +	if (cmd->rx_len >= master->maxdevs)
> +		newdevs = 0;
> +	else
> +		newdevs = GENMASK(master->maxdevs - cmd->rx_len - 1, 0);
>  	newdevs &= ~olddevs;
>  
>  	for (pos = 0; pos < master->maxdevs; pos++) {
> -- 
> 2.51.0
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com