The MPFS mailbox driver currently checks the BUSY bit at the start of mpfs_mbox_send() and immediately returns -EBUSY if the controller is busy.
On MPFS, BUSY may be transiently asserted during early boot even though no other U-Boot service is actively executing. In Linux, returning -EBUSY here is retryable via the mailbox framework and scheduler, but in U-Boot this results in a hard failure. Replace the immediate BUSY check with a bounded wait using regmap_read_poll_timeout(), waiting for the controller to become idle before issuing a new request. This preserves the intent of the BUSY check while avoiding spurious early-boot failures in U-Boot’s synchronous, polled execution model. The timeout is conservative and based on observed MPFS behaviour, where BUSY clears within a few milliseconds. Signed-off-by: Jamie Gibbons <[email protected]> --- drivers/mailbox/mpfs-mbox.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/mailbox/mpfs-mbox.c b/drivers/mailbox/mpfs-mbox.c index 165d9d89630..8b7a2719330 100644 --- a/drivers/mailbox/mpfs-mbox.c +++ b/drivers/mailbox/mpfs-mbox.c @@ -65,8 +65,11 @@ static int mpfs_mbox_send(struct mbox_chan *chan, const void *data) u32 *word_buf = (u32 *)msg->cmd_data; - if (mpfs_mbox_busy(chan)) - return -EBUSY; + ret = regmap_read_poll_timeout(mbox->control_scb, SERVICES_SR_OFFSET, + value, !(value & SERVICE_SR_BUSY_MASK), + 1, 20); + if (ret) + return ret; for (idx = 0; idx < (msg->cmd_data_size / BYTES_4); idx++) writel(word_buf[idx], mbox->mbox_base + msg->mbox_offset + idx * BYTES_4); -- 2.43.0
