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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iZDNr-0006py-Da; Mon, 25 Nov 2019 12:22:27 +0000 Received: from bhuna.collabora.co.uk ([46.235.227.227]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iZDNp-0006pN-1c for linux-i3c@lists.infradead.org; Mon, 25 Nov 2019 12:22:26 +0000 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id E6C9128FC86; Mon, 25 Nov 2019 12:22:21 +0000 (GMT) Date: Mon, 25 Nov 2019 13:22:19 +0100 From: Boris Brezillon To: Vitor Soares Subject: Re: I3C Mastership RFC Message-ID: <20191125132219.2e45d084@collabora.com> In-Reply-To: References: <20191112084127.6efc6fac@collabora.com> <20191114061011.GA25288@global.cadence.com> <20191114133214.0b6ecc0a@collabora.com> <20191125080220.GA30630@global.cadence.com> <20191125123452.7c2549dd@collabora.com> <20191125115502.GA5777@global.cadence.com> Organization: Collabora X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191125_042225_355040_7E65CB24 X-CRM114-Status: GOOD ( 32.93 ) X-BeenThere: linux-i3c@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux I3C List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Przemyslaw Gaj , "linux-i3c@lists.infradead.org" , "bbrezillon@kernel.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-i3c" Errors-To: linux-i3c-bounces+linux-i3c=archiver.kernel.org@lists.infradead.org On Mon, 25 Nov 2019 12:03:42 +0000 Vitor Soares wrote: > From: Przemyslaw Gaj > Date: Mon, Nov 25, 2019 at 11:55:16 > > > The 11/25/2019 11:42, Vitor Soares wrote: > > > > > > Hi Boris, > > > > > > From: Boris Brezillon > > > Date: Mon, Nov 25, 2019 at 11:34:52 > > > > > > > On Mon, 25 Nov 2019 11:19:44 +0000 > > > > Vitor Soares wrote: > > > > > > > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > > > > > > > > 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. The point is, at the end you can pick some parts of my sec > > > > > > > master code and integrate in your solution. > > > > > > > > > > > > > > > > > > > Can you point me to the version of the patch your changes are based on? > > > > > > And also, can you tell me what issues you faced? I would like to check > > > > > > if they are already adressed in my code. > > > > > > > > > > I used v3 and v4. From v5, I found useful the switch case (request, > > > > > deliver, handoff, takeover) in hc side. > > > > > > > > > > I didn't hardly test how device.c request mastership but I suspect it > > > > > won't work properly. When you do i3c_dev_do_priv_xfers_locked() you might > > > > > not be the master yet. > > > > > > > > I'm pretty sure we solved that already (that's what > > > > i3c_master_acquire_bus_ownership() calls are supposed to take care of). > > > > Can you be a bit more specific? What makes you think the master might > > > > not be in control of the bus when i3c_dev_do_priv_xfers_locked() is > > > > called? > > > > > > You are assuming that after i3c_master_acquire_bus_ownership() return, > > > secondary master already owns the bus. Main master can ack the MR request > > > and not send the CETACCMST immediately. > > > > > > > In Cadence HC driver, I'm waiting for GETACCMST longer, polling the > > status and after I exit from ->request_mastership(), I'm the bus owner. > > If not, error exit code is returned and we can't make the transfers. > > Are you able to implement the same behavior? > > You can assume everyone will do in that way. What happen if you receive a > request or an information from current master? We have this ->request_mastership() method so controllers that have this logic (MR+wait(GETACCMST) automated can still interface with the subsystem. If your controller handles the MR/GETACCMST separately, it shouldn't be hard to implement, and we can even provide an helper if people end up duplicating the code. _______________________________________________ linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c