linux-kernel - Re: [PATCHv10 2/4] mailbox: Introduce framework for mailbox

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Date:	Wed, 24 Sep 2014 12:14:19 -0400
From:	Ashwin Chaugule <ashwin.chaugule@...aro.org>
To:	Sudeep Holla <sudeep.holla@....com>
Cc:	Jassi Brar <jaswinder.singh@...aro.org>,
	Devicetree List <devicetree@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"ks.giri@...sung.com" <ks.giri@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Mark Rutland <Mark.Rutland@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Courtney Cavin <courtney.cavin@...ymobile.com>,
	Matt Porter <mporter@...aro.org>,
	Craig McGeachie <slapdau@...oo.com.au>,
	LeyFoon Tan <lftan.linux@...il.com>,
	Loic Pallardy <loic.pallardy@...com>,
	"Anna, Suman" <s-anna@...com>, Bjorn Andersson <bjorn@...o.se>,
	Patch Tracking <patches@...aro.org>,
	"mollie.wu@...aro.org" <mollie.wu@...aro.org>,
	Tetsuya Takinishi <t.takinishi@...fujitsu.com>,
	"broonie@...aro.org" <broonie@...aro.org>,
	Kevin Hilman <khilman@...aro.org>,
	"lee.jones@...aro.org" <lee.jones@...aro.org>,
	"andy.green@...aro.org" <andy.green@...aro.org>
Subject: Re: [PATCHv10 2/4] mailbox: Introduce framework for mailbox

On 22 September 2014 14:33, Sudeep Holla <sudeep.holla@....com> wrote:
> On 22/09/14 19:15, Sudeep Holla wrote:
>> On 22/09/14 19:01, Ashwin Chaugule wrote:
>>>
>>> Hi Jassi,
>>>
>>> On 1 August 2014 08:31, Jassi Brar <jaswinder.singh@...aro.org> wrote:
>>>>
>>>> Introduce common framework for client/protocol drivers and
>>>> controller drivers of Inter-Processor-Communication (IPC).
>>>>
>>>> Client driver developers should have a look at
>>>>    include/linux/mailbox_client.h to understand the part of
>>>> the API exposed to client drivers.
>>>> Similarly controller driver developers should have a look
>>>> at include/linux/mailbox_controller.h
>>>>
>>>> Signed-off-by: Jassi Brar <jaswinder.singh@...aro.org>
>>>> ---
>>>>    MAINTAINERS                        |   8 +
>>>>    drivers/mailbox/Makefile           |   4 +
>>>>    drivers/mailbox/mailbox.c          | 466
>>>> +++++++++++++++++++++++++++++++++++++
>>>>    include/linux/mailbox_client.h     |  46 ++++
>>>>    include/linux/mailbox_controller.h | 135 +++++++++++
>>>>    5 files changed, 659 insertions(+)
>>>>    create mode 100644 drivers/mailbox/mailbox.c
>>>>    create mode 100644 include/linux/mailbox_client.h
>>>>    create mode 100644 include/linux/mailbox_controller.h
>>>>
>>>
>>> [..]
>>>
>>>> +
>>>> +static void poll_txdone(unsigned long data)
>>>> +{
>>>> +       struct mbox_controller *mbox = (struct mbox_controller *)data;
>>>> +       bool txdone, resched = false;
>>>> +       int i;
>>>> +
>>>> +       for (i = 0; i < mbox->num_chans; i++) {
>>>> +               struct mbox_chan *chan = &mbox->chans[i];
>>>> +
>>>> +               if (chan->active_req && chan->cl) {
>>>> +                       resched = true;
>>>> +                       txdone = chan->mbox->ops->last_tx_done(chan);
>>>> +                       if (txdone)
>>>> +                               tx_tick(chan, 0);
>>>> +               }
>>>> +       }
>>>> +
>>>> +       if (resched)
>>>> +               mod_timer(&mbox->poll, jiffies +
>>>> +                               msecs_to_jiffies(mbox->period));
>>>
>>>
>>> While preparing a different patch which uses the Mbox framework, I
>>> noticed that mbox->period might not be initialized anywhere. Also, how
>>> is mbox->txpoll_period to be used? It appears from the description of
>>> txpoll_period in mbox_controller.h that you'd want to use that value
>>> in the mod_timer above, or equate the two somewhere in the controller
>>> registration or eliminate one of the two. FWIW I also looked at your
>>> code in [1].
>>>
>>
>> IIUC the controller needs to set the txpoll_period if it sets
>> txdone_poll, may be a sanity check for !0 would be good.
>>
>
> Ah, sorry I confused mbox->period to txpoll_period.
> You are right mbox->period is not set, the header claims it to be
> private, and hence I assume it needs to be handled only in core mailbox
> library. Not sure if we need both mbox->period and txpoll_period though.

Right. I dont see the need for having both either. Unless the Mailbox
maintainer wants to fix this in some other way, I can send a patch for
replacing mbox->period with mbox->txpoll_period along with my PCC
work.

Thanks,
Ashwin
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