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Revert "mailbox: avoid timer start from callback"

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This reverts commit c7dacf5b0f.

The Pi 400 shutdown/poweroff mechanism relies on being able to set
a GPIO on the expander in the pm_power_off handler, something that
requires two mailbox calls - GET_GPIO_STATE and SET_GPIO_STATE. A
recent kernel change introduces a reasonable possibility that the
GET call doesn't completes, and bisecting led to a commit from
October that changes the timer usage of the mailbox.

My theory is that there is a race condition in the new code that breaks
the poll timer, but that it normally goes unnoticed because subsequent
mailbox activity wakes it up again. The power-off mailbox calls happen
at a time when other subsystems have been shut down, so if one of them
fails then there is nothing to allow it to recover.

See: https://github.com/raspberrypi/linux/issues/3941

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
This commit is contained in:
Phil Elwell
2020-11-03 11:49:53 +00:00
committed by popcornmix
parent c27ff1ceb4
commit 66b7c6aa6a
1 changed files with 5 additions and 7 deletions
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12
drivers/mailbox/mailbox.c
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@@ -82,12 +82,9 @@ static void msg_submit(struct mbox_chan *chan)
exit:
spin_unlock_irqrestore(&chan->lock, flags);
/* kick start the timer immediately to avoid delays */
if (!err && (chan->txdone_method & TXDONE_BY_POLL)) {
/* but only if not already active */
if (!hrtimer_active(&chan->mbox->poll_hrt))
hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
}
if (!err && (chan->txdone_method & TXDONE_BY_POLL))
/* kick start the timer immediately to avoid delays */
hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
}
static void tx_tick(struct mbox_chan *chan, int r)
@@ -125,10 +122,11 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer)
struct mbox_chan *chan = &mbox->chans[i];
if (chan->active_req && chan->cl) {
resched = true;
txdone = chan->mbox->ops->last_tx_done(chan);
if (txdone)
tx_tick(chan, 0);
else
resched = true;
}
}