linux-kernel - Re: [PATCH 1/2] mailbox: reset txdone_method TXDONE_BY_POLL if client knows

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Date:   Mon, 3 Jul 2017 17:20:16 +0530
From:   Jassi Brar <jaswinder.singh@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexey Klimov <alexey.klimov@....com>
Subject: Re: [PATCH 1/2] mailbox: reset txdone_method TXDONE_BY_POLL if client knows_txdone

On 3 July 2017 at 15:05, Sudeep Holla <sudeep.holla@....com> wrote:
>
>
> On 03/07/17 09:57, Sudeep Holla wrote:
>>
>>
>> On 01/07/17 12:25, Jassi Brar wrote:
>>> On Fri, Jun 30, 2017 at 8:44 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>>>> Currently the mailbox framework sets txdone_method to TXDONE_BY_POLL if
>>>> the controller sets txdone_by_poll. However some clients can have a
>>>> mechanism to do TXDONE_BY_ACK which they can specify by knows_txdone.
>>>> However, we endup setting both TXDONE_BY_POLL and TXDONE_BY_ACK in that
>>>> case. In such scenario, we may end up with below warnings as the tx
>>>> ticker is run both by mailbox framework and the client.
>>>>
>>>> WARNING: CPU: 1 PID: 0 at kernel/time/hrtimer.c:805 hrtimer_forward+0x88/0xd8
>>>> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.12.0-rc5 #242
>>>> Hardware name: ARM LTD ARM Juno Development Platform
>>>> task: ffff8009768ca700 task.stack: ffff8009768f8000
>>>> PC is at hrtimer_forward+0x88/0xd8
>>>> LR is at txdone_hrtimer+0xd4/0xf8
>>>> Call trace:
>>>>  hrtimer_forward+0x88/0xd8
>>>>  __hrtimer_run_queues+0xe4/0x158
>>>>  hrtimer_interrupt+0xa4/0x220
>>>>  arch_timer_handler_phys+0x30/0x40
>>>>  handle_percpu_devid_irq+0x78/0x130
>>>>  generic_handle_irq+0x24/0x38
>>>>  __handle_domain_irq+0x5c/0xb8
>>>>  gic_handle_irq+0x54/0xa8
>>>>
>>>> This patch fixes the issue by resetting TXDONE_BY_POLL if client has set
>>>> knows_txdone.
>>>>
>>>> Cc: Alexey Klimov <alexey.klimov@....com>
>>>> Cc: Jassi Brar <jaswinder.singh@...aro.org>
>>>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>>>> ---
>>>>  drivers/mailbox/mailbox.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
>>>> index 537f4f6d009b..8da30f833262 100644
>>>> --- a/drivers/mailbox/mailbox.c
>>>> +++ b/drivers/mailbox/mailbox.c
>>>> @@ -351,7 +351,7 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
>>>>         init_completion(&chan->tx_complete);
>>>>
>>>>         if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
>>>> -               chan->txdone_method |= TXDONE_BY_ACK;
>>>> +               chan->txdone_method = TXDONE_BY_ACK;
>>>>
>>> It has to be restored back in mbox_free_channel()
>>
>> Ah right, will fix and repost.
>>
>
> I was too fast to response, I see we already take care of that in free
> channel. So I think it should be fine as is.
>
>         if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
>                 chan->txdone_method = TXDONE_BY_POLL;
>
You were too fast this time :)

chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK)

  is not same as

(chan->txdone_method == TXDONE_BY_POLL || chan->txdone_method == TXDONE_BY_ACK)