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 10:35:26 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jassi Brar <jassisinghbrar@...il.com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexey Klimov <alexey.klimov@....com>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH 1/2] mailbox: reset txdone_method TXDONE_BY_POLL if client
 knows_txdone



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;
-- 
Regards,
Sudeep