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From: Jeremy Linton <>
To: Lorenzo Pieralisi <>,
	Jon Masters <>
Cc: Bjorn Helgaas <>, Will Deacon <>,,,, lkml <>,
	Catalin Marinas <>,
	Bjorn Helgaas <>,
Subject: Re: [PATCH] arm64: PCI: Enable SMC conduit
Date: Thu, 25 Feb 2021 16:31:48 -0600	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


On 2/25/21 3:30 AM, Lorenzo Pieralisi wrote:
> On Thu, Feb 18, 2021 at 12:43:30PM -0500, Jon Masters wrote:
>> Hi Bjorn, all,
>> On Thu, Jan 28, 2021 at 6:31 PM Bjorn Helgaas <> wrote:
>>      On Tue, Jan 26, 2021 at 10:46:04AM -0600, Jeremy Linton wrote:
>>      > Does that mean its open season for ECAM quirks, and we can expect
>>      > them to start being merged now?
>>      "Open season" makes me cringe because it suggests we have a license to
>>      use quirks indiscriminately forever, and I hope that's not the case.
>>      Lorenzo is closer to this issue than I am and has much better insight
>>      into the mess this could turn into.  From my point of view, it's
>>      shocking how much of a hassle this is compared to x86.  There just
>>      aren't ECAM quirks, in-kernel clock management, or any of that crap.
>>      I don't know how they do it on x86 and I don't have to care.  Whatever
>>      they need to do, they apparently do in AML.  Eventually ARM64 has to
>>      get there as well if vendors want distro support.
>>      I don't want to be in the position of enforcing a draconian "no more
>>      quirks ever" policy.  The intent -- to encourage/force vendors to
>>      develop spec-compliant machines -- is good, but it seems like the
>>      reward of having compliant machines "just work" vs the penalty of
>>      having to write quirks and shepherd them upstream and into distros
>>      will probably be more effective and not much slower.
>> The problem is that the third party IP vendors (still) make too much junk. For
>> years, there wasn't a compliance program (e.g. SystemReady with some of the
>> meat behind PCI-SIG compliance) and even when there was the third party IP
>> vendors building "root ports" (not even RCs) would make some junk with a hacked
>> up Linux kernel booting on a model and demo that as "PCI". There wasn't the
>> kind of adult supervision that was required. It is (slowly) happening now, but
>> it's years and years late. It's just embarrassing to see the lack of ECAM that
>> works. In many cases, it's because the IP being used was baked years ago or
>> made for some "non server" (as if there is such a thing) use case, etc. But in
>> others, there was a chance to do it right, and it still happens. Some of us
>> have lost what hair we had over the years getting third party IP vendors to
>> wake up and start caring about this.
>> So there's no excuse. None at all. However, this is where we are. And it /is/
>> improving. But it's still too slow, and we have platforms still coming to
>> market that need to boot and run. Based on this, and the need to have something
>> more flexible than just solving for ECAM deficiencies (which are really just a
>> symptom), I can see the allure of an SMC. I don't like it, but if that's where
>> folks want to go, and if we can find a way to constrain the enthusiasm for it,
>> then perhaps it is a path forward. But if we are to go down that path it needs
>> to come with a giant warning from the kernel that a system was booted at is
>> relying on that. Something that will cause an OS certification program to fail
>> without a waiver, or will cause customers to phone up for support wondering why
>> the hw is broken. It *must* not be a silent thing. It needs to be "this
>> hardware is broken and non-standard, get the next version fixed".
> It is a stance I agree with in many respects, it should be shared (it
> was in HTML format - the lists unfortunately dropped the message) so I
> am replying to it to make it public.

So, the V3 of this set has a pr_info of "PCI: SMC conduit attached to 
segment %d". I will respin with that at pr_warn() which seems to fulfill 
the comment above. Is that "giant" enough, or should it be higher/worded 


  reply	other threads:[~2021-02-25 22:32 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-05  4:57 [PATCH] arm64: PCI: Enable SMC conduit Jeremy Linton
2021-01-07 15:28 ` Rob Herring
2021-01-07 16:23   ` Jeremy Linton
2021-01-07 17:36     ` Rob Herring
2021-01-07 19:45       ` Jeremy Linton
2021-01-07 20:35         ` Rob Herring
2021-01-07 18:14 ` Will Deacon
2021-01-07 19:18   ` Jeremy Linton
2021-01-07 21:05   ` Jon Masters
2021-01-07 21:49     ` Rob Herring
2021-01-08 10:32     ` Lorenzo Pieralisi
2021-01-22 19:48       ` Will Deacon
2021-01-26 16:46         ` Jeremy Linton
2021-01-26 22:54           ` Will Deacon
2021-01-28 18:50             ` Jeremy Linton
2021-01-28 23:31           ` Bjorn Helgaas
     [not found]             ` <>
2021-02-25  9:30               ` Lorenzo Pieralisi
2021-02-25 22:31                 ` Jeremy Linton [this message]
2021-01-26 17:08         ` Vikram Sethi
2021-01-26 22:53           ` Will Deacon
2021-03-25 13:12             ` Lorenzo Pieralisi
2021-03-25 20:45               ` Marcin Wojtas
2021-03-25 21:12                 ` Jon Masters
2021-03-26  9:27                   ` Marcin Wojtas
2021-06-16 17:36               ` Jason Gunthorpe
     [not found]                 ` <>
2021-06-18 14:05                   ` Jason Gunthorpe
2021-06-19 16:34                     ` Jon Masters
2021-06-19 16:38                       ` Jon Masters
2021-06-20  0:26                       ` Jason Gunthorpe
2021-06-18 15:10               ` Jeremy Linton
2021-01-12 16:16 ` Vidya Sagar
2021-01-12 16:57   ` Jeremy Linton

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