target/linux/bcm27xx/patches-5.15/950-0029-Revert-mailbox-avoid-timer-start-from-callback.patch

   1 From fe19823f6053fe91a671fdbf92ab93b517a25219 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"
   5
   6 This reverts commit c7dacf5b0f32957b24ef29df1207dc2cd8307743.
   7
   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.
  14
  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.
  20
  21 See: https://github.com/raspberrypi/linux/issues/3941
  22
  23 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
  24 ---
  25  drivers/mailbox/mailbox.c | 12 +++++-------
  26  1 file changed, 5 insertions(+), 7 deletions(-)
  27
  28 --- a/drivers/mailbox/mailbox.c
  29 +++ b/drivers/mailbox/mailbox.c
  30 @@ -82,12 +82,9 @@ static void msg_submit(struct mbox_chan
  31  exit:
  32         spin_unlock_irqrestore(&chan->lock, flags);
  33
  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);
  39 -       }
  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);
  43  }
  44
  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];
  48
  49                 if (chan->active_req && chan->cl) {
  50 -                       resched = true;
  51                         txdone = chan->mbox->ops->last_tx_done(chan);
  52                         if (txdone)
  53                                 tx_tick(chan, 0);
  54 +                       else
  55 +                               resched = true;
  56                 }
  57         }
  58