Messages in this thread | | | From | Przemyslaw Sroka <> | Subject | RE: [PATCH v2 2/7] i3c: Add core I3C infrastructure | Date | Tue, 27 Feb 2018 20:24:43 +0000 |
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Hi Boris
> -----Original Message----- > From: Boris Brezillon [mailto:boris.brezillon@bootlin.com] > Sent: Tuesday, February 27, 2018 9:13 PM > To: Przemyslaw Sroka <psroka@cadence.com> > Cc: Vitor Soares <Vitor.Soares@synopsys.com>; Boris Brezillon > <boris.brezillon@free-electrons.com>; Wolfram Sang <wsa@the- > dreams.de>; linux-i2c@vger.kernel.org; Jonathan Corbet <corbet@lwn.net>; > linux-doc@vger.kernel.org; Greg Kroah-Hartman > <gregkh@linuxfoundation.org>; Arnd Bergmann <arnd@arndb.de>; > Arkadiusz Golec <agolec@cadence.com>; Alan Douglas > <adouglas@cadence.com>; Bartosz Folta <bfolta@cadence.com>; Damian > Kos <dkos@cadence.com>; Alicja Jurasik-Urbaniak <alicja@cadence.com>; > Cyprian Wronka <cwronka@cadence.com>; Suresh Punnoose > <sureshp@cadence.com>; Thomas Petazzoni <thomas.petazzoni@free- > electrons.com>; Nishanth Menon <nm@ti.com>; Rob Herring > <robh+dt@kernel.org>; Pawel Moll <pawel.moll@arm.com>; Mark Rutland > <mark.rutland@arm.com>; Ian Campbell <ijc+devicetree@hellion.org.uk>; > Kumar Gala <galak@codeaurora.org>; devicetree@vger.kernel.org; linux- > kernel@vger.kernel.org; Geert Uytterhoeven <geert@linux-m68k.org>; Linus > Walleij <linus.walleij@linaro.org> > Subject: Re: [PATCH v2 2/7] i3c: Add core I3C infrastructure > > EXTERNAL MAIL > > > Hi Przemek, > > On Tue, 27 Feb 2018 16:43:27 +0000 > Przemyslaw Sroka <psroka@cadence.com> wrote: > > > > > > > >> Either important is the SETDASA for declared I3C devices. So the > > > >> DAA process should start by send an SETDASA and them ENTDAA > CCC > > > command. > > > > My understanding was that SETDASA was not mandatory, and was > only > > > > useful when one wants to assign a specific dynamic address to a > > > > slave that has a static address (which is again not mandatory). > > > > I've tested it, and even devices with a static address participate > > > > to the DAA procedure if they've not been assigned a dynamic > > > > address yet, so I don't see the need for this SETDASA step if you > > > > don't need to assign a particular dynamic address to the device. > > > > > > > > Could you tell me why you think SETDASA is required? > > > > > > Yes, you are right... But in my opinion it is required as it does > > > part of DAA process. > > > > SETDASA is simply faster than ENTDAA, but only if there is no need to > > collect BCR/DCR/PID of such devices. I think most applications would > > like to have them as an status information so after all ENTDAA can be > > regarded as an generic approach (unless I'm mistaken). > > Actually, we could retrieve BCR/DCR/PID (and all other relevant > information, like MAXDS) even with the SETDASA approach. We just need to > send the according CCC commands after SETDASA. > I agree, what I meant by "SETDASA is simply faster than ENTDAA, but only if there is no need to collect BCR/DCR/PID of such devices." Is that it is faster than DAA but only if not followed by GET CCC commands to gather BCR/DCR/PID. I think we are on the same page here.
> But that's also my understanding that ENTDAA should always work, and > SETDASA usage is only needed if you want to reserve a dynamic address > and assign it to a device before DAA takes place. This way you can enforce > the device priority (WRT IBIs). But honestly, that's the only use case I can > think of, and to me, it sounds like an advanced feature we may want to > support at some point, but don't need in the initial implementation. > Still ENTDAA seems to be sufficient for IBI prioritization but I can imagine some use cases where people would like to use it for such purposes. Note that SETDASA is applicable only for devices with SA so it is self-explanatory that it cannot be considered as utility to define priorities for all devices before ENTDAA.
> -- > Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and > Kernel engineering https://urldefense.proofpoint.com/v2/url?u=https- > 3A__bootlin.com&d=DwICAg&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3G > Z-_haXqY&r=b0WPdqYyu0KH4-vSatt-ViJE1riZ603zdXl3hHHp_TU&m=wM54- > BGcSfHEklVRsw02O-bnyNkLTe9c0RyBP_ExzPA&s=pxQrogG- > Nq4XOMU7SPZ2FZNbgnbnjdERtMm_h7ZcdCE&e=
Regards, Przemek
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