Re: [PATCH 1/3] mailbox: Add ability for clients to abort data in channel

[CK Hu <ck.hu@mediatek.com>]

Hi, Jassi:

On Wed, 2019-01-16 at 10:22 -0600, Jassi Brar wrote:
> On Tue, Jan 15, 2019 at 11:07 PM CK Hu <ck.hu@mediatek.com> wrote:
> >
> > This patch supplies a new framework API, mbox_abort_channel(), and
> > a new controller interface, abort_data().
> >
> > For some client's application, it need to clean up the data in channel
> > but keep the channel so it could send data to channel later.
> >
> > Signed-off-by: CK Hu <ck.hu@mediatek.com>
> > ---
> >  drivers/mailbox/mailbox.c          | 23 +++++++++++++++++++++++
> >  include/linux/mailbox_client.h     |  1 +
> >  include/linux/mailbox_controller.h |  4 ++++
> >  3 files changed, 28 insertions(+)
> >
> > diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> > index c6a7d4582dc6..281647162c76 100644
> > --- a/drivers/mailbox/mailbox.c
> > +++ b/drivers/mailbox/mailbox.c
> > @@ -428,6 +428,29 @@ struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
> >  }
> >  EXPORT_SYMBOL_GPL(mbox_request_channel_byname);
> >
> > +/**
> > + * mbox_abort_channel - The client abort all data in a mailbox
> > + *                     channel by this call.
> > + * @chan: The mailbox channel to be aborted.
> > + */
> > +void mbox_abort_channel(struct mbox_chan *chan)
> > +{
> > +       unsigned long flags;
> > +
> > +       if (!chan || !chan->cl)
> > +               return;
> > +
> > +       if (chan->mbox->ops->abort_data)
> > +               chan->mbox->ops->abort_data(chan);
> > +
> > +       /* The queued TX requests are simply aborted, no callbacks are made */
> > +       spin_lock_irqsave(&chan->lock, flags);
> > +       chan->cl = NULL;
> > +       chan->active_req = NULL;
> > +       spin_unlock_irqrestore(&chan->lock, flags);
> > +}
> >
> Why not just release and then request channel again ?
> mbox_abort_channel() is just a copy of mbox_free_channel() and if the
> abort can sleep, that is more reason to just do that.

The cursor may change position 300 times in one second, so I still
concern the processing time. Request and free channel looks too heavy to
do 300 times per second. Conceptually, I just want to clean up the
channel rather than free and request it, so they are somewhat different.
I say it may sleep because mbox_abort_channel() is a copy of
mbox_free_channel(). I could change it to 'must not sleep' because
Mediatek controller does not sleep in abort callback.

Regards,
CK