Dave Gerlach <d-gerlach@xxxxxx> 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@xxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
