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SubjectRe: [PATCH 0/4] Broadcom STB PM PSCI extensions
On Fri, Jan 21, 2022 at 07:54:17PM -0800, Florian Fainelli wrote:
> Hi all,

Hi Florian,

> This patch series contains the Broadcom STB PSCI extensions which adds
> some additional functions on top of the existing standard PSCI interface
> which is the reason for having the driver implement a custom
> suspend_ops.

I *really* don't like the idea of having non-standard PSCI extensions, because
it somewhat defeats the point of PSCI being a standard, and opens the door for
the zoo of mechanisms we had on 32-bit.

I think this needs a fair amount more explanation and justification.

> These platforms have traditionally supported a mode that is akin to
> ACPI's S2 with the CPU in WFI and all of the chip being clock gated
> which is entered with "echo standby > /sys/power/state". Additional a
> true suspend to DRAM as defined in ACPI by S3 is implemented with "echo
> mem > /sys/power/state".

Why isn't a combination of CPU_SUSPEND and SYSTEM_SUSPEND sufficient here?

What specifically *can't* you do with standard PSCI calls?

> These platforms also may have an external Broadcom PMIC chip which can
> cause the SoC to be powercycled assuming that we communicate that intent
> via a vendor specific PSCI SYSTEM_RESET2.
>
> Since it is desirable to get any new functionality added to the kernel
> to be loadable as a module as part of shipping said products in a Google
> Kernel Image (GKI) environment, we need to export a couple of symbols from
> drivers/firmware/psci/psci.c.

I really don't want to export the guts of psci.c.

Thanks,
Mark.

> Thanks for your feedback.
>
> Florian Fainelli (4):
> firmware: psci: Export a couple of suspend symbols
> soc: bcm: brcmstb: Make legacy PM code depend on !ARM_PSCI_FW
> soc: bcm: brcmstb: Added support for PSCI system suspend operations
> Documentation: ABI: Document Broadcom STB PSCI firmware files
>
> .../ABI/testing/sysfs-firmware-brcmstb | 16 +
> drivers/firmware/psci/psci.c | 9 +-
> drivers/soc/bcm/brcmstb/Kconfig | 4 +-
> drivers/soc/bcm/brcmstb/pm/Makefile | 3 +
> drivers/soc/bcm/brcmstb/pm/pm-psci.c | 315 ++++++++++++++++++
> include/linux/psci.h | 2 +
> include/linux/soc/brcmstb/brcmstb-smccc.h | 84 +++++
> 7 files changed, 430 insertions(+), 3 deletions(-)
> create mode 100644 Documentation/ABI/testing/sysfs-firmware-brcmstb
> create mode 100644 drivers/soc/bcm/brcmstb/pm/pm-psci.c
> create mode 100644 include/linux/soc/brcmstb/brcmstb-smccc.h
>
> --
> 2.25.1
>

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