Quoting Stephen Boyd (2021-03-23 15:43:36)
> 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: 5/6 up/down: 509/-4401 (-3892)
> 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
> 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=66737606, After=66733714, 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.
>
> Cc: Elliot Berman <eberman@xxxxxxxxxxxxxx>
> Cc: Brian Masney <masneyb@xxxxxxxxxxxxx>
> Cc: Stephan Gerhold <stephan@xxxxxxxxxxx>
> Cc: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
> Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> ---
>
Elliot, can you ack/review this?
> Followup to v1 (https://lore.kernel.org/r/20210223214539.1336155-7-swboyd@xxxxxxxxxxxx):
> * Don't change the legacy file to use legacy calls only
> * Wrap more things in CONFIG_ARM checks
>
