From owner-freebsd-hackers@FreeBSD.ORG Wed Mar 5 22:44:25 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id DE61789B for ; Wed, 5 Mar 2014 22:44:25 +0000 (UTC) Received: from mail-ig0-f169.google.com (mail-ig0-f169.google.com [209.85.213.169]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 9FC23927 for ; Wed, 5 Mar 2014 22:44:25 +0000 (UTC) Received: by mail-ig0-f169.google.com with SMTP id h18so9653689igc.0 for ; Wed, 05 Mar 2014 14:44:24 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:content-type:mime-version:subject:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to; bh=HOq1Ddfp1unL9wCPfgLIjB5qtYWTIUKcoPHCR3P70ZU=; b=cq5/P04TAK9wh6jVvUDSj7TuBd+ONqxdZaj6h4QjlC3lPqj52nFNcbr7+WhtGZXIHg L/ev6PrB3VRM6nbh4JmrYr9SRaL2MkOJLWx8+eeUBQfXQfazndW5CpdHM20IkOIgR7j8 MoS/aN9HOc2IK4PiuY9Zn88yCcBvgpW03J+wr3XB4srgPHQ7lqT8ot1AdUGgPUyE8i3V YzsHyvv1cAcEBLXDV5X3xZJdnO+Lqwg/OCgdVdyCJbkj2zbGmXV9u5ubhWz3iAkOHWNv /XNhEhCG/dYHYOEJ/n20CfGwNgt0Jdfz70NnpNGimwHfLEJf8ZwdtXcZu6PfH8zvhMYi V6Tw== X-Gm-Message-State: ALoCoQnoZZkVB8nIX5c283cWPYjlqry1npb/nlfObUTB6y31YzZqV7fSu6mdssHn4K68T/vizNIA X-Received: by 10.50.47.79 with SMTP id b15mr12006255ign.12.1394059464805; Wed, 05 Mar 2014 14:44:24 -0800 (PST) Received: from netflix-mac.bsdimp.com (50-78-194-198-static.hfc.comcastbusiness.net. [50.78.194.198]) by mx.google.com with ESMTPSA id f1sm17748349igy.2.2014.03.05.14.44.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 05 Mar 2014 14:44:24 -0800 (PST) Sender: Warner Losh Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.2 \(1874\)) Subject: Re: [PATCH] simplebus child device probe order control via FDT (motivated by BeagleBone Black) From: Warner Losh In-Reply-To: Date: Wed, 5 Mar 2014 15:44:22 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <39ED4040-2A6A-4D85-97D5-DCDE4ECCA0EC@bsdimp.com> References: <7C2B7036-51CC-4C97-80C4-0A439874357D@bsdimp.com> <1393939277.1149.300.camel@revolution.hippie.lan> <438620C4-7712-4B01-A46F-CB57946A30BF@bsdimp.com> <16A5203B-B06D-4129-A54F-F34D5FA28D2B@bsdimp.com> To: Patrick Kelsey X-Mailer: Apple Mail (2.1874) Cc: "freebsd-hackers@freebsd.org" , freebsd-arm , freebsd-embedded@freebsd.org, Ian Lepore X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Mar 2014 22:44:25 -0000 On Mar 5, 2014, at 2:56 PM, Patrick Kelsey wrote: >=20 >=20 >=20 > On Wed, Mar 5, 2014 at 4:24 PM, Warner Losh wrote: >=20 > On Mar 5, 2014, at 11:55 AM, Patrick Kelsey wrote: >=20 > > > > > > > > On Wed, Mar 5, 2014 at 8:31 AM, Warner Losh wrote: > > > > On Mar 4, 2014, at 11:53 PM, Patrick Kelsey wrote: > > > > > > > > > > > > > > On Tue, Mar 4, 2014 at 8:21 AM, Ian Lepore = wrote: > > > > > > There's a standard property for mmc/sd devices, "non-removable" = whose > > > presence denotes things like soldered-on eMMC parts. Only one of = our > > > many sdhci drivers supports it right now (imx). In general the = core > > > part of the driver (dev/sdhci) doesn't have good support for > > > insert/remove/presence detection that's handled off to the side = (whether > > > it's non-removable or a gpio pin). > > > > > > That alone doesn't solve the wider problem, though, which I think = breaks > > > down into two pieces. Let's say you've got two slots, call them = left > > > and right. You end up with these two problems... > > > > > > * Sometimes the right slot is mmcsd0, but it turns into = mmcsd1 if > > > there's a card in the left slot when I boot; I don't want = it to > > > change. > > > > > > And not just a boot-time issue, of course. If you were to remove = those two cards and then reinsert them in the opposite time-order, their = device names would swap. > > > > > > * I want the slot on the left to be named '1' and the right = to be > > > '0'. > > > > > > The first problem is easily solved without impacting dts in any = way. We > > > just wire down the relationship controllerN -> mmcN -> mmcsdN. = This is > > > exactly equivelent to the old ATA_STATIC_ID option in its effect = -- you > > > don't get to choose the names, but you know they won't change = based on > > > which devices are present. It could be controlled with a tunable. > > > > > > It's harder to envision the fix for the second part without adding = an > > > ad-hoc property for the devices. Even with a property I'm not = sure how > > > easy it would be. > > > > > > We should be able to assign a geographic address = (controllerX:slotY) to each mmcsd device in a given system (let's ignore = for now the theoretical possibility of multiple cards on one bus). The = 'controllerX' part of the address could be the controller's pathname = from the devicetree, or an index assigned by mmcbr machinery at attach = time. The "slotY" part of the address is assigned by the specific = controller device driver using some internally-determined fixed mapping = between the assigned values and its physical slots. This geographic = address could be used to create an additional set of /dev entries with = stable names. There could be a mechanism for user-configurable aliases = for the geographical addresses. > > > > There=92s already a chance to run a script when a device is attached = that can create /dev/slot0 or /dev/slot1 that has geographical = information available to it. People use ddvd for this in the USB world = all the time to make sure that tty devices get a symlink based on their = location or serial number. > > > > Why is mmc so different it needs its own mechanism? > > > > I'm laying out my view of the information that would be needed and = the types of actions that would have to be taken based on that = information to solve the issue. I'm not saying devd can't be the piece = that is used to implement the actions (indeed, I noted devd as a = potential building block for a solution in my initial response). I'm = also not saying mmc needs its own mechanism, I'm saying it needs /a/ = mechanism, and so far there still seems to be something missing (because = it's not there, or I'm still ignorant of it). > > > > What seems to be missing is geographical addressing for mmc devices. > > > > I think what you might be saying is that the existing mmcsd = add/remove code could be augmented to send devctl notifications, along = the lines of: > > > > devctl_notify("MMC", "DEVICE", "ATTACH"|"DETACH", "... = controller=3D = slot=3D rca=3D") > > > > and then I and the fine author of devctl and devd would be pleased. >=20 > MMC doesn=92t need anything special here. That=92s already present. = Looking at the device tree we see on one of the platforms that=92s handy = for me to access: >=20 > at91_mci0 > mmc0 > mmcsd0 at rca=3D0xb368 >=20 > So you know that mmcsd0 is on mmc0 bus attached to at91_mci0, which is = ultimately the FDT node where things came from. There=92s not a = user-defined slot associated with this (and we should have a SLOT A vs = SLOT B as a location info for this platform, because we can have two = cards on the one bus in the MMC case), true, but for your use case I = don=92t think that you need it. We should be attaching the host = controller regardless of whether the or not there=92s a card in there, = so it will be fixed. While some additional information would be useful = to publish, I don=92t think your use case requires it=85 >=20 >=20 > The reason you need something extra here is that what is there now = breaks down whenever you don't have a one-to-one mapping between = controllers and buses. Any controller with more than one slot can yield = something of the form: >=20 > sdhci0 > mmc0 > mmcsd0 at rca=3D0xabcd > mmc1 > mmcsd1 at rca=3D0x1234 >=20 > and you have no idea what physical slot in the system mmcsd0 and = mmcsd1 are in. The driver isn=92t going to be able to help you, because it reports mmc0 = based on the data it gets from slot 0 status registers, and mmc1 based = on slot 1 status registers. Since there=92s no notion of how that maps = to physical hardware, the driver can=92t do anything automatically. And = since mmc on down is populated by FreeSBD, there=92s no hints in the FDT = tree for them. > For my immediate use case, sure, I can rely on the one-to-one = relationship between controllers and buses. At this point, though, = rather than skate by on that happy coincidence, I'd rather invest what = now seems to be a rather small amount of effort adding mmcsd devctl = notifications that would cover the multiple-slots-per-controller case as = well, and then build the rest of what I want on top of that information = coming out of ddvd. Trouble is, how do we know what to send with this new notification. = That=92s the part I=92m having trouble with. Where does that data come = from? And how is it different than what=92s in the device tree? > On the at91 platform cited above, that allows you to connect two MMC = cards to the same bus (i.e., multidrop configuration), is there any way = to distinguish which card is in which physical slot? I'm still under = the impression that this is the one case where we aren't going to be = able to determine the physical location of every mmcsd device. Actually, there=92s two different configurations, I believe. One that = supports two SD cards (SLOT A / SLOT B) and one that supports MMC multi = drop. The former has been tested at least once, while the latter I don=92t= think had ever been checked. Warner=