Messages in this thread | | | Date | Sun, 22 Oct 2023 17:09:09 +0800 | From | Yu-Chien Peter Lin <> | Subject | Re: [RFC PATCH v2 07/10] perf: RISC-V: Move T-Head PMU to CPU feature alternative framework |
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Hi Conor,
On Fri, Oct 20, 2023 at 10:05:20AM +0100, Conor Dooley wrote: > On Fri, Oct 20, 2023 at 04:54:58PM +0800, Yu-Chien Peter Lin wrote: > > On Thu, Oct 19, 2023 at 05:13:00PM +0100, Conor Dooley wrote: > > > On Thu, Oct 19, 2023 at 10:01:19PM +0800, Yu Chien Peter Lin wrote: > > > > > > $subject: perf: RISC-V: Move T-Head PMU to CPU feature alternative framework > > > > > > IMO, this should be "RISC-V, perf:" or just "RISC-V" as the changes > > > being made to the arch code are far more meaningful than those > > > elsewhere. > > > > OK will update the subject to "RISC-V:" > > > > > > The custom PMU extension was developed to support perf event sampling > > > > prior to the ratification of Sscofpmf. Instead of utilizing the standard > > > > bits and CSR of Sscofpmf, a set of custom CSRs is added. So we may > > > > consider it as a CPU feature rather than an erratum. > > > > > > > > T-Head cores need to append "xtheadpmu" to the riscv,isa-extensions > > > > for each cpu node in device tree, and enable CONFIG_THEAD_CUSTOM_PMU > > > > for proper functioning as of this commit. > > > > > > And in doing so, you regress break perf for existing DTs :( > > > You didn't add the property to existing DTS in-kernel either, so if this > > > series was applied, perf would just entirely stop working, no? > > > > Only `perf record/top` stop working I think. > > > > There are too many users out there, and don't have the boards to > > test, so leave those DTS unchanged, it would be great if T-Head > > community could help to check/update their DTS. > > So, there are too many users to add xtheadpmu to the devicetrees, but > not too many users to make changes that will cause a regression? > I'm not following the logic here, sorry.
humm, I'll try. I assume that the sun20i-d1s.dtsi is all I need to update for T-Head PMU.
> > > > Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com> > > > > --- > > > > Hi All, > > > > > > > > This is in preparation for introducing other PMU alternative. > > > > We follow Conor's suggestion [1] to use cpu feature alternative > > > > framework rather than errta, if you want to stick with errata > > > > alternative or have other issues, please let me know. Thanks. > > > > > > Personally, I like this conversion, but it is going to regress support > > > for perf on any T-Head cores which may be a bitter pill to get people to > > > actually accept... > > > Perhaps we could add this "improved" detection in parallel, and > > > eventually remove the m*id based stuff in the future. > > > > > > > [1] https://patchwork.kernel.org/project/linux-riscv/patch/20230907021635.1002738-4-peterlin@andestech.com/#25503860 > > > > > > > > Changes v1 -> v2: > > > > - New patch > > > > --- > > > > > @@ -805,7 +816,8 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pde > > > > if (riscv_isa_extension_available(NULL, SSCOFPMF)) { > > > > riscv_pmu_irq_num = RV_IRQ_PMU; > > > > riscv_pmu_use_irq = true; > > > > - } else if (IS_ENABLED(CONFIG_ERRATA_THEAD_PMU) && > > > > + } else if (riscv_isa_extension_available(NULL, XTHEADPMU) && > > > > + IS_ENABLED(CONFIG_THEAD_CUSTOM_PMU) && > > > > riscv_cached_mvendorid(0) == THEAD_VENDOR_ID && > > > > riscv_cached_marchid(0) == 0 && > > > > riscv_cached_mimpid(0) == 0) { > > > > > > Can all of the m*id checks be removed, since the firmware is now > > > explicitly telling us that the T-Head PMU is supported? > > > > I can only comfirm that boards with "allwinner,sun20i-d1" compatible > > string uses the T-Head PMU device callbacks. > > I'm not sure how that is an answer to my question.
Sorry for that unclear answer. Yes, I agree we no longer need to check the m*id here.
In OpenSBI, it appears that allwinner D1 is the only platform that has T-Head PMU support, the other T-Head platforms need to ensure that the callbacks [1] are registered in order to work with SBI PMU driver in kernel.
Regards, Peter Lin
[1] https://github.com/riscv-software-src/opensbi/blob/v1.3.1/platform/generic/allwinner/sun20i-d1.c#L263-L272
> Thanks, > Conor.
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