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

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Date:   Sat, 1 Jul 2017 16:55:04 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     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 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()

thanks