On 20 June 2014 10:47, Bjorn Andersson <bjorn@xxxxxxx> wrote: > On Wed, Jun 18, 2014 at 9:44 AM, Kevin Hilman <khilman@xxxxxxxxxx> wrote: > [...] >> Thinking more about what this RPM driver actually does, and since you >> mentioned patterns across SoCs, it seems to me the RPM driver bascially >> just doing the IPC. >> > > Yes, technically this is IPC. But it's all exposed in memory as if it > was hardware, so there's no messages or packets to be interpreted by > the other side. > >> So, rather than MFD or drivers/soc, it seems to me that it should be >> implmented as a controller in the new common mailbox framwork[1] being >> worked on by Jassi Brar (added to Cc.) >> >> IIUC, RPM is actually only doing one-way IPC (it only exposes a write() >> interface to clients) so it seems like a rather simple implementation of >> a mailbox controller. >> > > What I think you miss here is the detail of that what the regulator > writes is not what is passed over the IPC, but rather is just an > interface to abstract away how things are spread our in the register > space. > > So the only place where we do have a "mailbox" here is the actual > function call between the regulator and the rpm drivers; not between > the rpm driver and the rpm. > Is the RPM a firmware running on a separate processor outside the scope of Linux ? Is an irq raised to the RPM when you do writel(RPM_SIGNAL, rpm->ipc_rpm_reg) ? Do you get the qcom_rpm_ack_interrupt() only when the RPM firmware has taken action on Linux's request (i.e, values filled in 80ish registers)? I maybe wrong but I think the answer to all above is Yes, and that is the reason I think its no different than other mailbox controllers. For example, look at pl320_ipc_transmit() >> I believe Bjorn is already on the list of folks Cc'd on the common >> mailbox framework, so it would be good to hear from him why RPM wouldn't >> fit under that framework. >> > > In a separate group of Qualcomm platforms the communication with the > RPM is done by passing messages over a shared memory channel; as this > requires a completely different implementation of the rpm driver, I > have started to look at Jassi's patch series. > > Unfortunately at this point it does not look like the proposed mailbox > framework would reduce the complexity of the implementation nor > provide any additional benefits when it comes to being able to > exchange the underlaying communication methods. > For your simple one-way communication, using mailbox api isn't going to change lives. Cheers, -Jassi -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
