Messages in this thread | | | Subject | Re: [PATCH] arm64: PCI: Enable SMC conduit | From | Jeremy Linton <> | Date | Thu, 25 Feb 2021 16:31:48 -0600 |
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Hi,
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 <helgaas@kernel.org> 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 differently?
Thanks,
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