From: Stephen Warren <swarren@wwwdotorg.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: devicetree@vger.kernel.org,
Linux Kernel list <linux-kernel@vger.kernel.org>,
m.szyprowski@samsung.com, swarren@nvidia.com,
rob.herring@calxeda.com, Grant Likely <grant.likely@secretlab.ca>
Subject: Re: "memory" binding issues
Date: Mon, 16 Sep 2013 10:17:46 -0600 [thread overview]
Message-ID: <52372F2A.2050003@wwwdotorg.org> (raw)
In-Reply-To: <1379300274.4098.77.camel@pasglop>
On 09/15/2013 08:57 PM, Benjamin Herrenschmidt wrote:
> [resent to the right list this time around]
>
> Hi folks !
>
> So I don't have the bandwidth to follow closely what's going on, but I
> just today noticed the crackpot that went into 3.11 as part of commit:
>
> 9d8eab7af79cb4ce2de5de39f82c455b1f796963
> drivers: of: add initialization code for dma reserved memory
>
> Fist of all, do NOT add (or change) a binding as part of a patch
> implementing code, it's gross.
Personally, I would argue the opposite; it's much easier to see what's
going on when it's all together in one patch. Ensuring ABI stability can
only be achieved through code review, i.e. splitting into separate
DT/code patches won't achieve that, so that argument doesn't affect this.
...
> Additionally, it has the following issues:
>
> - It describes the "memory" node as /memory, which is WRONG
>
> It should be "/memory@unit-address, this is important because the Linux
> kernel of_find_device_by_path() isn't smart enough to do partial
> searches (unlike the real OFW one) and thus to ignore the unit address
> for search purposes, and you *need* the unit address if you have
> multiple memory nodes (which you typically do on NUMA machines).
Perhaps /memory should have had a unit-address, but it never has had on
ARM; see arch/arm/boot/dts/skeleton.dtsi which says:
memory { device_type = "memory"; reg = <0 0>; };
... and the fact that reg in /memory can have multiple entries seems to
support the expectation we only have a single node here. I'm not sure
how we could possibly change this now it's become so entrenched?
WARNING: multiple messages have this Message-ID (diff)
From: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
To: Benjamin Herrenschmidt
<benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Linux Kernel list
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org,
swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org,
rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org,
Grant Likely
<grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
Subject: Re: "memory" binding issues
Date: Mon, 16 Sep 2013 10:17:46 -0600 [thread overview]
Message-ID: <52372F2A.2050003@wwwdotorg.org> (raw)
In-Reply-To: <1379300274.4098.77.camel@pasglop>
On 09/15/2013 08:57 PM, Benjamin Herrenschmidt wrote:
> [resent to the right list this time around]
>
> Hi folks !
>
> So I don't have the bandwidth to follow closely what's going on, but I
> just today noticed the crackpot that went into 3.11 as part of commit:
>
> 9d8eab7af79cb4ce2de5de39f82c455b1f796963
> drivers: of: add initialization code for dma reserved memory
>
> Fist of all, do NOT add (or change) a binding as part of a patch
> implementing code, it's gross.
Personally, I would argue the opposite; it's much easier to see what's
going on when it's all together in one patch. Ensuring ABI stability can
only be achieved through code review, i.e. splitting into separate
DT/code patches won't achieve that, so that argument doesn't affect this.
...
> Additionally, it has the following issues:
>
> - It describes the "memory" node as /memory, which is WRONG
>
> It should be "/memory@unit-address, this is important because the Linux
> kernel of_find_device_by_path() isn't smart enough to do partial
> searches (unlike the real OFW one) and thus to ignore the unit address
> for search purposes, and you *need* the unit address if you have
> multiple memory nodes (which you typically do on NUMA machines).
Perhaps /memory should have had a unit-address, but it never has had on
ARM; see arch/arm/boot/dts/skeleton.dtsi which says:
memory { device_type = "memory"; reg = <0 0>; };
... and the fact that reg in /memory can have multiple entries seems to
support the expectation we only have a single node here. I'm not sure
how we could possibly change this now it's become so entrenched?
--
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next prev parent reply other threads:[~2013-09-16 16:17 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-16 2:57 "memory" binding issues Benjamin Herrenschmidt
2013-09-16 2:57 ` Benjamin Herrenschmidt
2013-09-16 15:22 ` Kumar Gala
2013-09-16 15:22 ` Kumar Gala
2013-09-16 22:42 ` Benjamin Herrenschmidt
2013-09-17 15:53 ` Kumar Gala
2013-09-17 15:53 ` Kumar Gala
2013-09-16 16:17 ` Stephen Warren [this message]
2013-09-16 16:17 ` Stephen Warren
2013-09-16 22:46 ` Benjamin Herrenschmidt
2013-09-16 22:46 ` Benjamin Herrenschmidt
2013-09-16 22:48 ` Olof Johansson
2013-09-16 22:48 ` Olof Johansson
2013-09-16 23:47 ` Benjamin Herrenschmidt
2013-09-16 23:47 ` Benjamin Herrenschmidt
2013-09-16 23:48 ` Olof Johansson
2013-09-17 1:37 ` Benjamin Herrenschmidt
2013-09-17 1:37 ` Benjamin Herrenschmidt
2013-09-17 7:56 ` Tomasz Figa
2013-09-17 7:56 ` Tomasz Figa
2013-09-17 16:43 ` Olof Johansson
2013-09-17 16:43 ` Olof Johansson
2013-09-17 21:08 ` Frank Rowand
2013-09-17 21:08 ` Frank Rowand
2013-09-17 21:15 ` Olof Johansson
2013-09-17 21:15 ` Olof Johansson
2013-09-17 21:19 ` Tomasz Figa
2013-09-17 21:19 ` Tomasz Figa
2013-09-17 21:33 ` Olof Johansson
2013-09-17 23:04 ` Benjamin Herrenschmidt
2013-09-17 23:04 ` Benjamin Herrenschmidt
2013-09-17 23:25 ` Olof Johansson
2013-09-17 23:25 ` Olof Johansson
2013-09-17 21:56 ` Benjamin Herrenschmidt
2013-09-17 21:56 ` Benjamin Herrenschmidt
2013-09-18 16:28 ` Stephen Warren
2013-09-18 16:28 ` Stephen Warren
2013-09-19 0:29 ` David Gibson
2013-09-19 0:29 ` David Gibson
2013-09-18 1:25 ` David Gibson
2013-09-18 1:25 ` David Gibson
2013-09-18 1:31 ` Grant Likely
2013-09-18 1:31 ` Grant Likely
2013-09-18 1:38 ` Grant Likely
2013-09-18 8:08 ` Benjamin Herrenschmidt
2013-09-18 8:08 ` Benjamin Herrenschmidt
2013-09-18 2:57 ` Grant Likely
2013-09-18 2:57 ` Grant Likely
2013-09-18 8:21 ` Benjamin Herrenschmidt
2013-09-18 8:21 ` Benjamin Herrenschmidt
2013-09-27 15:42 ` Kumar Gala
2013-09-27 15:42 ` Kumar Gala
2013-10-03 15:04 ` Kumar Gala
-- strict thread matches above, loose matches on Subject: below --
2013-09-16 2:41 Benjamin Herrenschmidt
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