ppc September 2021

ppc@lists.fedoraproject.org

2 participants
4 discussions

Power support for Fedora beyond IBM POWER (e.g. Libre-SOC)?
by Robert Scheck 10 Dec '21

10 Dec '21

Good evening, my interest in Power architecture got started when I read in February 2020 about the new open license model on a well-known German news ticker [1]. I attended the OpenPOWER Virtual Summit 2020 North America [2] in September and heard there the first time about Libre-SOC [3], previously also known as Libre-RISCV SoC [4] before they switched from RISC-V to Power. During FOSDEM 2021, I noticed their LibreSOC Project stand [5] and asked multiple beginner questions, which Luke Kenneth Casson Leighton (on Cc) nicely took care of (thank you!). Given an idea is a Power-based SBC [6], I wondered whether I could just run a Fedora for ppc64le (which seems to currently target POWER8 LE and later), on it. Unfortunately Luke's answer was no, because LibreSOC won't support VSX [7], which are IBM's SIMD (six hundred?) instructions, but the LibreSOC Project plans to have Simple-V Vectorisation according to their FOSDEM talk [8]. Note, the A2O POWER processor core [9] doesn't support VSX, too (same seems to apply to A2I and Microwatt, but they're either POWER7 or likely not powerful enough for typical PC usage anyway -> outside of Fedora's target?). Trying to follow the path on how to get Fedora for ppc64le to a "POWER-Pi", I had to learn that glibc developers seem to treat IBM POWER9 strictly equal to ABI rules rather handling the different features more fine granulated. My understanding here might be imprecise or wrong, this is what I understood and I'm no expert at this topic. Nevertheless I'm trying to precise it a bit more: The IBM Power ISA Version 3.1 [10] specifies on page 8 compliancy subsets, where the Linux Compliancy Subset (LCS) is explained on page 10 ff. Page 11 refers specifically to the "Scalar Float Optional Features" and mentions in the first row of the table VSX. However what seems to be implemented e.g. in glibc is something like "#ifdef POWER9" rather "#ifdef HARDWAREFEATURE", which effectively makes VSX support mandatory rather optional. Given the only publicly known modern implementor of VSX right now, not on an EOL schedule, seems to be IBM's POWER9, it would from my point of view be helpful that VSX support in at least glibc is made optional. When asking whether the new glibc-hwcaps [11] could be a solution, Luke's answer read for me like a conditional "yes", because at least VSX should be covered by glibc-hwcaps then (again, same as above...my understanding, I'm still no expert here). But this is why I'm Cc-ing here Florian Weimer, who implemented [12] this new glibc feature. I'm not sure if Florian is the right person for this topic at all, but maybe he knows the right people? :) Finally, to close the circle to the subject of my mail: (how) can we reach Power support for Fedora (and other mainstream Linux distributions) beyond IBM POWER (e.g. Libre-SOC)? [1] https://www.heise.de/newsticker/meldung/Prozessor-ISA-Power-OpenPower-Found… [2] https://openpowerfoundation.org/events/openpower-summit-2020-north-america/ [3] https://libre-soc.org/ [4] http://lists.libre-riscv.org/pipermail/libre-riscv-dev/2019-October/thread.… [5] https://stands.fosdem.org/stands/the_libresoc_project__a_hybrid_3d_cpu_vpu_… [6] https://libre-soc.org/22nm_PowerPI/ [7] https://en.wikipedia.org/wiki/AltiVec#VSX_.28Vector_Scalar_Extension.29 [8] https://fosdem.org/2021/schedule/event/the_libresoc_project_simple_v_vector… [9] https://openpowerfoundation.org/a-deep-dive-into-a2i-and-a2o/ [10] https://ibm.ent.box.com/s/hhjfw0x0lrbtyzmiaffnbxh2fuo0fog0 [11] https://sourceware.org/pipermail/libc-announce/2021/000030.html [12] https://sourceware.org/pipermail/libc-alpha/2020-June/115250.html Regards, Robert

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Bug Pipewire with dedicated sound cards
by Maurizio M 03 Sep '21

03 Sep '21

Good morning Dan I can confirm that by eliminating PipeWire and reinstalling Pulse-audio, the system returns to work in a regular and perfect way. I therefore confirm that the bug is specific to Pipewire and you have to work on it, you can confirm everything to the developers. For specific information I remember that I use a dedicated sound card that has always been supported by Linux, namely the RME HDSPE-AIO. Having said that I hope that you will also work to improve the management of Gnome 40 which currently on Power architecture is really horrendous. Thanks for everything best regards Maurizio MauryG5

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Re: Problems with Fedora 34
by Maurizio Mileto Principale 02 Sep '21

02 Sep '21

Hi Dan, no I haven't tried it because I didn't know about the procedure, I hadn't read that part. I found the command to return to Pulse Audio: $ sudo dnf swap --allowerasing pipewire-pulseaudio pulseaudio I'll try and let you know so we can actually see if that's the problem. Thanks, I'll write to you as soon as I've done the test.

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Re: Problems with Fedora 34
by Maurizio Mileto Principale 02 Sep '21

02 Sep '21

Hi Dan, sorry for the delay in answering, yes I can tell you that the card has always worked regularly on all the Fedora that I have used up to now ie 31, 32, and 33, without any kind of problem. Similarly it works on all versions I've tried of Debian and Ubuntu without Pulse Audio. So I think so, since you switched to Pipewere see, the card has stopped working and so I'm sure the problem lies in the new Pipewere sound system ... Can you do something? I think it will be difficult to receive numerous reports as this card is very expensive and little used in general and that is why I report the anomaly because I am afraid that if it is not solved immediately, it will end up not working anymore in any distro being that all sooner or later they will pass on Pipewere ...

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ppc September 2021