Re: I3C Mastership RFC

[Przemyslaw Gaj <pgaj@cadence.com>]

The 11/14/2019 15:50, Boris Brezillon wrote:
> 
> On Thu, 14 Nov 2019 14:17:38 +0000
> Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> 
> > From: Boris Brezillon <boris.brezillon@collabora.com>
> > Date: Thu, Nov 14, 2019 at 12:32:14
> > 
> > > Hi Vitor,
> > > 
> > > On Thu, 14 Nov 2019 11:56:00 +0000
> > > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> > >   
> > > > Hi,
> > > > 
> > > > From: Przemyslaw Gaj <pgaj@cadence.com>
> > > > Date: Thu, Nov 14, 2019 at 06:10:12
> > > >   
> > > > > Hi Vitor,
> > > > > 
> > > > > The 11/12/2019 08:41, Boris Brezillon wrote:    
> > > > > > 
> > > > > > Hi Vitor,
> > > > > > 
> > > > > > On Mon, 11 Nov 2019 12:30:45 +0000
> > > > > > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> > > > > >     
> > > > > > > Hi Boris and Przemek,
> > > > > > > 
> > > > > > > I have a working version for tests purposes. Yet, I have some basic TODOS 
> > > > > > > to address during the takeover of the bus.    
> > > > > > 
> > > > > > Okay. Would you mind sharing a branch with this material so Przemek and
> > > > > > I can have a look at it?    
> > > > > 
> > > > > So, Vitor, can you share your changes? Can you tell me what you had to
> > > > > change to make it work? Also, which patch version is this based on?    
> > > > 
> > > > I'm closing a task and after that I will prepare the RFC.  
> > > 
> > > Okay, can we have an estimate? Are we talking about days or weeks?  
> > 
> > I will prioritize it for next week.
> 
> Great!
> 
> > 
> > >   
> > > > 
> > > > I based in all version and tried to pass everything to master.c file.  
> > > 
> > > I'm not sure what that means, but okay.
> > >   
> > > > Right now my challenge it to trigger mastership request when a device 
> > > > driver want to access to the bus but I believe we can discuss that after.  
> > > 
> > > That's kind of a basic feature when talking about mastership handover,
> > > but sure, we can discuss it after your RFC has been posted.  
> > 
> > I need to test if the time that device.c request the mastership and the 
> > controller has effectively the ownership of the bus is short enough to 
> > call i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers) before of all 
> > housekeeping of bus takeover.
> 
> We sorted that out in Przemek series already. Please base your work on
> what Przemek did (or at least look at it carefully), otherwise we're
> going to re-do/re-review the same things we did a few months back.
> 

Yes, that's how my patch series works. When device wants to transfer
data, mastership is requested automatically.

> > 
> > > 
> > > Note that I'm not super happy to have to go back to square 1 and throw
> > > away all of the work done by Przemek, especially since Przemek was the
> > > first one to post a patchset and he never really said he didn't
> > > want or didn't have time to continue working on this task (not even
> > > mentioning the time I spent reviewing those patches...).
> > > 
> > > If Przemek is fine with this situation I'm okay making an exception,
> > > but be aware that it's not how we usually do: the person that posts a
> > > patchset first leads the thing (of course, it's even better if there's
> > > some kind of coordination before the patch is posted).  
> > 
> > Honestly it looks like I'm competing on this which is not the case.
> > I just pointed out my concerns about this adoption because I see several 
> > issues on it.
> 
> Couldn't these problems/limitations be addressed in the existing
> implementation instead of re-implementing everything?
> 
> > The point is, at the end you can pick some parts of my sec 
> > master code and integrate in your solution.
> 
> I wish you had tried to modify what Przemek started instead of starting
> from scratch... Now someone will have to do the integration, but let's
> move on. Please post an RFC (or a public branch) as soon as possible,
> even if it's incomplete. It can even be something that doesn't compile.
> The idea being to check what's missing/wrong in Przemek implementation
> and see how we can merge the two.
> 
> > 
> > As I said previous for I3C spec 1.1 secondary master received a big 
> > improvement due the misunderstanding published in 1.0 spec.
> 
> Okay, I can't tell. Version 1.0 was already pretty clear to me with
> regard to mastership handover.
> 
> > I don't know 
> > any other protocol that implement such kind of feature and for this is 
> > from far the most complex feature to implement in SO based systems from 
> > i3c spec.
> 
> That's where the fun is, isn't it? :P
> 
> > 
> > > 
> > > BTW, you mentioned working on a lot of different topics, but most of
> > > them were left unfinished (userspace i3cdev interface, I3C slave
> > > framework/API, ...).  
> > 
> > The i3cdev does what we discuss during the proposal of i3c subsystem and 
> > only expose i3c device without device driver yet I'm not happy with 
> > transfer struct.
> > For the tools I have for hdr and sdr transfers, for now I didn't feel the 
> > need of a tool for ccc (but for testing purposes it would help a lot).
> 
> What about the I3C slave controller API/framework? Would be interesting
> to have someone work on that topic, and you seemed to be worried about
> how it would interact with masters that expose a real slave profile, so
> looking at it would be a good starting point IMHO.

-- 
-- 
Przemyslaw Gaj

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