Re: [PATCH v8 2/3] CMDQ: Mediatek CMDQ driver

From: Jassi Brar <jaswinder.singh@linaro.org>
To: Horng-Shyang Liao <hs.liao@mediatek.com>
Cc: Jassi Brar <jassisinghbrar@gmail.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Daniel Kurtz <djkurtz@chromium.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Devicetree List <devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com,
	Sascha Hauer <kernel@pengutronix.de>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Nicolas Boichat <drinkcat@chromium.org>,
	CK HU <ck.hu@mediatek.com>, cawa cheng <cawa.cheng@mediatek.com>,
	Bibby Hsieh <bibby.hsieh@mediatek.com>,
	YT Shen <yt.shen@mediatek.com>,
	Daoyuan Huang <daoyuan.huang@mediatek.com>,
	Damon Chu <damon.chu@mediatek.com>,
	Josh-YC Liu <josh-yc.liu@mediatek.com>,
	Glory Hung <glory.hung@mediatek.com>,
	Jiaguang Zhang <jiaguang.zhang@mediatek.com>,
	Dennis-YC Hsieh <dennis-yc.hsieh@mediatek.com>,
	Monica Wang <monica.wang@mediatek.com>
Subject: Re: [PATCH v8 2/3] CMDQ: Mediatek CMDQ driver
Date: Mon, 6 Jun 2016 18:47:02 +0530	[thread overview]
Message-ID: <CAJe_ZhfHQLW02pqyrSuSCHayT_7f1aaeg8cH9RAK16Skg9+3Jw@mail.gmail.com> (raw)
In-Reply-To: <1465205633.25607.33.camel@mtksdaap41>

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On 6 June 2016 at 15:03, Horng-Shyang Liao <hs.liao@mediatek.com> wrote:

> Hi Matthias, Jassi,
>
> On Fri, 2016-06-03 at 18:41 +0530, Jassi Brar wrote:
> > On Fri, Jun 3, 2016 at 4:48 PM, Matthias Brugger <matthias.bgg@gmail.com>
> wrote:
> > > On 03/06/16 08:12, Horng-Shyang Liao wrote:
> > >> On Thu, 2016-06-02 at 10:46 +0200, Matthias Brugger wrote:
> >
> > >>> I keep thinking about how to get rid of the two data structures,
> > >>> task_busy_list and the task_release_wq. We need the latter for the
> only
> > >>> sake of getting a timeout.
> > >>>
> > >>> Did you have a look on how the mailbox framework handles this?
> > >>> By the way, what is the reason to not implement the whole driver as a
> > >>> mailbox controller? For me, this driver looks like a good fit.
> > >>
> > >>
> > >> CMDQ needs to encode commands for GCE hardware. We think this behavior
> > >> should be put in CMDQ driver, and client just call CMDQ functions.
> > >> Therefore, if we want to use mailbox framework, cmdq_rec must be
> > >> mailbox client, and the others must be mailbox controller.
> > >>
> > >
> > > You mean the functions to fill the cmdq_rec and execute it?
> > > I think this should be part of the driver.
> > >
> > > Jassi, can you have a look on the interface this driver exports [0].
> > > They are needed to actually create the message which will be send.
> > > Could something like this be part of a mailbox driver?
> > >
> > > [0] https://patchwork.kernel.org/patch/9140221/
> > >
> > Packet creating/parsing should not be a part of controller driver. As
> > the log of this patch says, today it is used for only display but in
> > future it could work with other h/w as well, so it makes sense to have
> > mailbox api do the message queuing, the controller driver do the
> > send/receive and client drivers implement display and other h/w
> > specific packaging of data (protocol handling).
> >
> > So yes, I think this could use mailbox api.
> >
> > Cheers.
>
>
> Let me use display as an example to do some further explanation
> about CMDQ in advance. You can think CMDQ is a shadow register
> replacement. Therefore, we use cmdq_rec_write(_mask), cmdq_rec_wfe, and
> cmdq_rec_clear_event instead of accessing registers, and use
> cmdq_rec_flush(_async) instead of atomic swap.
>
> If we use mailbox to do the message queue, we can use mailbox framework
> to implement flush and callback. However, I don't think mailbox is
> suitable for cmdq_rec_write(_mask), cmdq_rec_wfe, and
> cmdq_rec_clear_event since they are just record some commands. Is this
> the same as your comment "Packet creating/parsing should not be a part
> of controller driver."?
>
> Therefore, do you mean we use mailbox framework to implement flush and
> callback and keep other interfaces?

Yes, implement flush and callback in mailbox controller driver and keep
other interfaces in mailbox client driver(s).

Cheers.

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