1 From a8fb0d43b8acd25d68a0d2c24fd0260393148447 Mon Sep 17 00:00:00 2001
2 From: Phil Elwell <phil@raspberrypi.com>
3 Date: Tue, 3 Nov 2020 11:49:53 +0000
4 Subject: [PATCH] Revert "mailbox: avoid timer start from callback"
6 This reverts commit c7dacf5b0f32957b24ef29df1207dc2cd8307743.
8 The Pi 400 shutdown/poweroff mechanism relies on being able to set
9 a GPIO on the expander in the pm_power_off handler, something that
10 requires two mailbox calls - GET_GPIO_STATE and SET_GPIO_STATE. A
11 recent kernel change introduces a reasonable possibility that the
12 GET call doesn't completes, and bisecting led to a commit from
13 October that changes the timer usage of the mailbox.
15 My theory is that there is a race condition in the new code that breaks
16 the poll timer, but that it normally goes unnoticed because subsequent
17 mailbox activity wakes it up again. The power-off mailbox calls happen
18 at a time when other subsystems have been shut down, so if one of them
19 fails then there is nothing to allow it to recover.
21 See: https://github.com/raspberrypi/linux/issues/3941
23 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
25 drivers/mailbox/mailbox.c | 12 +++++-------
26 1 file changed, 5 insertions(+), 7 deletions(-)
28 --- a/drivers/mailbox/mailbox.c
29 +++ b/drivers/mailbox/mailbox.c
30 @@ -82,12 +82,9 @@ static void msg_submit(struct mbox_chan
32 spin_unlock_irqrestore(&chan->lock, flags);
34 - /* kick start the timer immediately to avoid delays */
35 - if (!err && (chan->txdone_method & TXDONE_BY_POLL)) {
36 - /* but only if not already active */
37 - if (!hrtimer_active(&chan->mbox->poll_hrt))
38 - hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
40 + if (!err && (chan->txdone_method & TXDONE_BY_POLL))
41 + /* kick start the timer immediately to avoid delays */
42 + hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
45 static void tx_tick(struct mbox_chan *chan, int r)
46 @@ -125,10 +122,11 @@ static enum hrtimer_restart txdone_hrtim
47 struct mbox_chan *chan = &mbox->chans[i];
49 if (chan->active_req && chan->cl) {
51 txdone = chan->mbox->ops->last_tx_done(chan);