Quoting Elliot Berman (2021-03-03 19:35:08)
>
> On 2/23/2021 1:45 PM, Stephen Boyd wrote:
> > These scm calls are never used outside of legacy ARMv7 based platforms.
> > That's because PSCI, mandated on arm64, implements them for modern SoCs
> > via the PSCI spec. Let's move them to the legacy file and only compile
> > the legacy file into the kernel when CONFIG_ARM=y. Otherwise provide
> > stubs and fail the calls. This saves a little bit of space in an
> > arm64 allmodconfig >
> > $ ./scripts/bloat-o-meter vmlinux.before vmlinux.after
> > add/remove: 0/8 grow/shrink: 5/7 up/down: 509/-4405 (-3896)
> > Function old new delta
> > __qcom_scm_set_dload_mode.constprop 312 452 +140
> > qcom_scm_qsmmu500_wait_safe_toggle 288 416 +128
> > qcom_scm_io_writel 288 408 +120
> > qcom_scm_io_readl 376 492 +116
> > __param_str_download_mode 23 28 +5
> > __warned 4327 4326 -1
> > qcom_iommu_init 272 268 -4
> > e843419@0b3f_00010432_324 8 - -8
> > qcom_scm_call 228 208 -20
> > CSWTCH 5925 5877 -48
> > _sub_I_65535_1 163100 163040 -60
> > _sub_D_65535_0 163100 163040 -60
> > qcom_scm_wb 64 - -64
> > qcom_scm_lock 320 160 -160
> > qcom_scm_call_atomic 212 - -212
> > qcom_scm_cpu_power_down 308 - -308
> > scm_legacy_call_atomic 520 - -520
> > qcom_scm_set_warm_boot_addr 720 - -720
> > qcom_scm_set_cold_boot_addr 728 - -728
> > scm_legacy_call 1492 - -1492
> > Total: Before=66737642, After=66733746, chg -0.01%
> >
> > Commit 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and
> > legacy conventions") didn't mention any motivating factors for keeping
> > the legacy code around on arm64 kernels, i.e. presumably that commit
> > wasn't trying to support these legacy APIs on arm64 kernels.
>
> There are arm targets which support SMCCC convention and use some of
> these removed functions. Can these functions be kept in qcom-scm.c and
> wrapped with #if IS_ENABLED(CONFIG_ARM)?
>
It can be wrapped in qcom-scm.c, but why? It's all the same object file
so I'm lost why it matters. I suppose it would make it so the struct
doesn't have to be moved around and declared in the header? Any other
reason? I moved it to the legacy file so that it was very obvious that
the API wasn't to be used except for "legacy" platforms that don't use
PSCI.
