[PATCH v3] i3c: dw: reduce do_daa time if there's no client

[PATCH v3] i3c: dw: reduce do_daa time if there's no client

[Jisheng Zhang]

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 the existing rx_count >= maxdevs check then reports an empty bus.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---

since v2:
 - rebase on the lastest i3c/next
 - collect Reviewed-by tag

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 | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 0a3799a4ce87..4563d8761ba0 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -921,6 +921,7 @@ 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) |
-- 
2.51.0

Re: [PATCH v3] i3c: dw: reduce do_daa time if there's no client

[Alexandre Belloni]

On Wed, 19 Aug 2026 12:48:33 +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.
> 
> [...]

Applied, thanks!

[1/1] i3c: dw: reduce do_daa time if there's no client
      https://git.kernel.org/i3c/c/cab40cfc9e11

Best regards,

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