Re: [PATCH 0/3] Allow specifying an S2RAM sleep on pre-SYSTEM_SUSPEND PSCI impls

[Elliot Berman <quic_eberman@quicinc.com>]

On Mon, Oct 28, 2024 at 03:22:56PM +0100, Konrad Dybcio wrote:
> Certain firmwares expose exactly what PSCI_SYSTEM_SUSPEND does through
> CPU_SUSPEND instead. Inform Linux about that.
> Please see the commit messages for a more detailed explanation.
> 
> This is effectively a more educated follow-up to [1].
> 
> The ultimate goal is to stop making Linux think that certain states
> only concern cores/clusters, and consequently setting
> pm_set_suspend/resume_via_firmware(), so that client drivers (such as
> NVMe, see related discussion over at [2]) can make informed decisions
> about assuming the power state of the device they govern.
> 
> If this series gets green light, I'll push a follow-up one that wires
> up said sleep state on Qualcomm SoCs across the board.
> 
> [1] https://lore.kernel.org/linux-arm-kernel/20231227-topic-psci_fw_sus-v1-0-6910add70bf3@linaro.org/
> [2] https://lore.kernel.org/linux-nvme/20241024-topic-nvmequirk-v1-1-51249999d409@oss.qualcomm.com/
> 

I got a bit confused, but I think I might've pieced it together. Konrad
wants to support s2ram (not clear why) on Qualcomm SoCs from 2015-2023.
On these SoCs, PSCI_SYSTEM_SUSPEND (s2ram) isn't supported but doing
s2idle gets you the same effect. You'd like s2ram to work, so you
provide a way to replace the PSCI_SYSTEM_SUSPEND param with
(effectively) the CPU_SUSPEND command. If this is the wrong
understanding, please correct me.

Could patch 2 be sent separately? I think it seems fine without the
rest of the series.

I'm not sure why you'd like to support s2ram. Is it *only* that you'd
like to be able to set pm_set_supend/resume_via_firmware()? I hope this
doesn't sound silly: what if you register a platform_s2idle_ops for the
relevant SoCs which calls pm_set_suspend/resume_via_firwmare()?

- Elliot