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From fe19823f6053fe91a671fdbf92ab93b517a25219 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Tue, 3 Nov 2020 11:49:53 +0000
Subject: [PATCH] Revert "mailbox: avoid timer start from callback"
This reverts commit c7dacf5b0f32957b24ef29df1207dc2cd8307743.
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>
---
drivers/mailbox/mailbox.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -82,12 +82,9 @@ static void msg_submit(struct mbox_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_hrtim
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;
}
}
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