Re: [PATCH 6/6] firmware: qcom_scm: Only compile legacy calls on ARM

[Elliot Berman]

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)?