[PATCH] i3c: renesas: Don't register devices when ENTDAA times out

[Frank Li]

On Fri, Jul 31, 2026 at 09:01:46AM +0200, Tommaso Merciai wrote:
> renesas_i3c_daa() derives the number of newly assigned dynamic addresses
> from cmd->rx_count, which the response ISR sets 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.
>
> On a bus with no target connected the ENTDAA times out and the driver
> registers RENESAS_I3C_MAX_DEVS devices that are not there, each costing
> the core two seconds on a GETPID that can only time out:
>
>   i3c i3c-0: Failed to add I3C device at address 9, error -110
>   ...
>   i3c i3c-0: Failed to add I3C device at address 16, error -110
>
> Start from maxdevs instead: no address is assigned before ENTDAA runs,
> and the existing rx_count >= maxdevs check then reports an empty bus.
>
> Fixes: d028219a9f14 ("i3c: master: Add basic driver for the Renesas I3C controller")
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr at bp.renesas.com>
> ---

Does https://lore.kernel.org/linux-i3c/alUZ_N9VdxkhcpqM@lizhi-Precision-Tower-5810/

fix the same problem?

Frank

>  drivers/i3c/master/renesas-i3c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i3c/master/renesas-i3c.c b/drivers/i3c/master/renesas-i3c.c
> index 2b501f31e874..f4d9608978a9 100644
> --- a/drivers/i3c/master/renesas-i3c.c
> +++ b/drivers/i3c/master/renesas-i3c.c
> @@ -685,7 +685,7 @@ static int renesas_i3c_daa(struct i3c_master_controller *m)
>
>  	init_completion(&xfer->comp);
>  	cmd = xfer->cmds;
> -	cmd->rx_count = 0;
> +	cmd->rx_count = i3c->maxdevs;
>
>  	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(i3c->dev, pm);
>  	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
> --
> 2.54.0
>