Hi Ohad, From: ext Ohad Ben-Cohen <ohad@xxxxxxxxxx> Subject: Re: [PATCH v3 4/4] omap: mailbox: convert block api to kfifo Date: Tue, 15 Jun 2010 06:43:21 +0200 > Hi Hiroshi, > > On Mon, Jun 14, 2010 at 3:58 AM, Hiroshi DOYU <Hiroshi.DOYU@xxxxxxxxx> wrote: >> Does dspbridge really need its own defered work for sending mailbox >> messages? > > We do, according to > > http://permalink.gmane.org/gmane.linux.ports.arm.omap/38240 I am wondering that this defered work may not be necessary just for the serialization. > (thanks Rene for the explanation). > >> For recieving, its defered work(tasklet) can be trigered directly in >> the above proposed callback, that callback can triger its own >> workqueue if necessary, then. > > Agree > >> I think that, for recieving, some PM >> command may has to be sent back immedieately inside of >> tasklet. omap_mbox_msg_send_sync() may handle this case. > > Not sure how much QoS is an issue with mailbox (do we really have > latency issues ?), but I guess adding such interface can't hurt. This solves the one case of lockdep issue. >> I think that workqueue is only necessary when it has to sleep, >> otherwise tasklet is prefered. > > I must say I disagree; tasklets are really not friendly to the whole > system's responsiveness and should be used only if really needed > (there was even an attempt to remove them entirely in the past: > http://lwn.net/Articles/239633/). Evoking a workqueue may be overkilling just for putting several bytes into registers since large part of contents is usually passed through shared memory. >> I'd like to allow mutiple listners in some way, as the flexibility of >> mailbox functionalty. > > This can be achieved using notifier chains of multiple listeners > callback, but I agree with Felipe: do we really want this > functionality ? I just rather not add code that no one is going to > use. > > What do you say we start with enforcing only 1 listener and later, if > the use case of several listeners shows up, we'd add that support > (promise! :) ? Fair enough. -- 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
