From: khilman@kernel•org (Kevin Hilman)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4 10/11] ARM: OMAP2+: AM33XX: Basic suspend resume support
Date: Tue, 09 Sep 2014 14:10:16 -0700 [thread overview]
Message-ID: <7hr3zk7b5z.fsf@deeprootsystems.com> (raw)
In-Reply-To: <540F62E3.6080804@ti.com> (Dave Gerlach's message of "Tue, 9 Sep 2014 15:28:19 -0500")
Dave Gerlach <d-gerlach@ti•com> writes:
> Kevin/Ohad,
> On 09/09/2014 02:59 PM, Suman Anna wrote:
>> Hi Ohad,
>>
>> On 09/09/2014 05:31 AM, Ohad Ben-Cohen wrote:
>>> On Tue, Sep 9, 2014 at 1:30 AM, Kevin Hilman <khilman@linaro•org> wrote:
>>>> To me, it's not terribly clear how you made the split between this PM
>>>> core code an the remoteproc code. In the changelog for the remoteproc
>>>> patch, it states it's to "load the firmware for and boot the wkup_m3".
>>>> But, while parts of the IPC are here in pm33xx.c, parts of the IPC are
>>>> also inside the remoteproc driver, so I'm quite curious if that's OK
>>>> with the remoteproc maintainers. Either way, please make it clearer how
>>>> and why you made the split, and please isolate the wkup_m3 IPC/protocol
>>>> from this code. Think of people wanting to rework/extend the wkup_m3
>>>> firmware. They shouldn't be messing around in here, but rather inside a
>>>> driver specificaly for the wkup_m3.
>>>
>>> I haven't looked at the code very thoroughly yet, but generally a
>>> remoteproc driver should only implement the three start/stop/kick
>>> rproc_ops, and then register them via the remoteproc framework.
>>> Exposing additional API directly from that driver isn't something we
>>> immediately want to accept.
>>>
>>> If relevant, we would generally prefer to extend remoteproc instead,
>>> so other platform-specific drivers could utilize that functionality as
>>> well. Or rpmsg - if we're missing some IPC functionality.
>>
>> The WkupM3 cannot access DDR, and so we don't intend to use rpmsg. The
>> IPC with wkup_m3 is usually one of the last steps for putting the SoC
>> into a desired low-power state either during suspend or cpuidle, and the
>> communication uses a bank of fixed registers. The .kick is specific
>> to virtio-based communication, and so this is not gonna be used.
>>
>> If you can take a closer look at the wkup_m3 remoteproc driver and give
>> your comments, then we can plan on the next steps. Especially as there
>> are also pieces pertaining to the PM layer knowing the WkupM3 has been
>> loaded and booted. There are already some pending comments on code
>> fragments from Santosh and myself, but let us know your inputs on the
>> integration aspects on PM, remoteproc and IPC with WkupM3.
>>
>
> The split was defined by putting all the application specific (to the
> firmware in use) code in the platform pm code while trying to keep all the
> IPC code within the wkup_m3_rproc driver.
I don't even see that split. I see the platform PM code directly
setting IPC register values, but then rproc driver actually sends the
mailbox command.
> The exposed API is definitely heavily biased towards the intended
> use-case,
Maybe if the API was actually documented, it would be easier for us to
review it.
> but the CM3 was designed with this exact purpose in mind and
> not much else, and due to the limited IPC registers we have to work
> with there isn't a whole lot of flexibility. Only IPC reg 0 is always
> used as the resume address, the usage of the other registers is
> defined by the firmware and pm code.
>
> Just as a refresher for those not familiar with it, the IPC mechanism works
> like this: we load the ipc registers (8 for am33xx, 16 for am43xx) with any
> information we want to communicate to the CM3,
OK, and this happens currently in the platform PM code, right?
> then we make a dummy write to
> the Mailbox which triggers an interrupt on the CM3, the CM3 does what it
> needs to with the info passed in the IPC regs and writes anything it wants to
> communicate back to these registers, and then triggers a different interrupt
> (not related to mailbox) to let the MPU know it is done.
And this part happens in the rproc driver, right?
> It's kind of a mess so I figured one driver was the best way to
> encapsulate it all,
So where is this "one driver" that encapsulates it all?
> and I still had to
> introduce callbacks within the wkup_m3_rproc driver so it could let the pm code
> know when the FW loaded (to actually enable pm) and when an interrupt was
> received from the wkup_m3 (so the pm code can process the response).
> As Suman stated, this sequence is part of the suspend path and also will be part
> of the lower c-states for cpuidle, so we need something fast and lightweight.
> RPMsg is way more than we need and it doesn't really fit the use case, so I'm
> not sure what makes the most sense, extending remoteproc in some way to support
> IPC communication like described above or leaving the basic FW loading
> functionality in place in remoteproc but moving the IPC and wkup_m3
> functionality back into the platform pm33xx code as it's so specific to that
> use-case anyway.
I'm not advocating for using rpmsg (anymore). But I dont' think shoving
your rpmsg-lite IPC into your rproc driver is the right answer either
(and Ohad's repsonse confirmed my suspicion.)
What I think you need to do (and what I've recommended at least once in
earlier reviews) put all the (non-rproc) wkup_m3 IPC into into one
driver and create a well-described, well-documented API that the
platform PM code will use.
IMO, the current "split" is very difficult to read/understand, which
means it will even more difficult to maintain.
Kevin
next prev parent reply other threads:[~2014-09-09 21:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-11 2:55 [PATCH v4 00/11] ARM: OMAP2+: AM33XX: Add suspend-resume support Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 01/11] ARM: omap: edma: add suspend suspend/resume hooks Dave Gerlach
2014-07-14 11:05 ` Tony Lindgren
2014-07-14 17:47 ` Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 02/11] memory: emif: Move EMIF register defines to include/linux/ Dave Gerlach
2014-07-14 11:12 ` Tony Lindgren
2014-07-14 17:42 ` Dave Gerlach
2014-07-15 6:38 ` Tony Lindgren
2014-07-16 2:44 ` Dave Gerlach
2014-07-16 8:33 ` Tony Lindgren
2014-07-11 2:55 ` [PATCH v4 03/11] ARM: OMAP2+: timer: Add suspend-resume callbacks for clkevent device Dave Gerlach
2014-07-14 11:15 ` Tony Lindgren
2014-07-14 14:37 ` Santosh Shilimkar
2014-07-14 17:42 ` Dave Gerlach
2014-07-15 6:48 ` Tony Lindgren
2014-07-15 19:10 ` Dave Gerlach
2014-07-16 20:17 ` Dave Gerlach
2014-07-17 8:16 ` Tony Lindgren
2014-07-11 2:55 ` [PATCH v4 04/11] ARM: OMAP2+: Use pdata-quirks for wkup_m3 deassert_hardreset Dave Gerlach
2014-07-14 18:48 ` Suman Anna
2014-07-11 2:55 ` [PATCH v4 05/11] Documentation: dt: add ti,am3353_wkup_m3 bindings Dave Gerlach
2014-07-14 14:41 ` [PATCH v4 05/11] Documentation: dt: add ti, am3353_wkup_m3 bindings Santosh Shilimkar
2014-07-14 16:33 ` Suman Anna
2014-07-14 17:45 ` Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 06/11] remoteproc: wkup_m3: Add wkup_m3 remote proc driver Dave Gerlach
2014-07-14 14:54 ` Santosh Shilimkar
2014-07-14 17:43 ` Dave Gerlach
2014-07-14 19:07 ` Suman Anna
2014-07-14 21:09 ` Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 07/11] ARM: dts: am33xx: Update wkup_m3 node Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 08/11] ARM: OMAP2+: AM33XX: Reserve memory to comply with EMIF spec Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 09/11] ARM: OMAP2+: AM33XX: Add assembly code for PM operations Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 10/11] ARM: OMAP2+: AM33XX: Basic suspend resume support Dave Gerlach
2014-09-08 22:30 ` Kevin Hilman
2014-09-09 10:31 ` Ohad Ben-Cohen
2014-09-09 19:59 ` Suman Anna
2014-09-09 20:28 ` Dave Gerlach
2014-09-09 21:10 ` Kevin Hilman [this message]
2014-09-10 21:19 ` Dave Gerlach
2014-09-16 15:08 ` Ohad Ben-Cohen
2014-09-16 16:14 ` Suman Anna
2014-09-17 13:37 ` Ohad Ben-Cohen
2014-09-25 19:42 ` Dave Gerlach
2014-07-11 2:55 ` [PATCH v4 11/11] ARM: OMAP2+: AM33XX: Hookup AM33XX PM code into OMAP builds Dave Gerlach
2014-07-14 11:21 ` Tony Lindgren
2014-07-14 17:46 ` Dave Gerlach
2014-07-11 7:59 ` [PATCH v4 00/11] ARM: OMAP2+: AM33XX: Add suspend-resume support Daniel Mack
2014-07-11 17:24 ` Dave Gerlach
2014-07-11 15:30 ` Andre Heider
2014-07-11 17:31 ` Dave Gerlach
2014-07-14 9:37 ` Andre Heider
2014-07-14 11:24 ` Tony Lindgren
2014-07-14 17:47 ` Dave Gerlach
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