Re: [PATCH v1 1/1] riscv: sbi: Introduce system suspend support

Andrew Jones
2023-10-12T13:36:50Z

On Thu, Oct 12, 2023 at 02:30:02PM +0100, Conor Dooley wrote:
> Yo,
>
> On Thu, Oct 12, 2023 at 09:21:50AM +0200, Andrew Jones wrote:
> > When the SUSP SBI extension is present it implies that the standard
> > "suspend to RAM" type is available. Wire it up to the generic
> > platform suspend support, also applying the already present support
> > for non-retentive CPU suspend. When the kernel is built with
> > CONFIG_SUSPEND, one can do 'echo mem > /sys/power/state' to suspend.
> > Resumption will occur when a platform-specific wake-up event arrives.
> >
> > Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
>
> > +static int __init sbi_system_suspend_init(void)
> > +{
> > + if (!sbi_spec_is_0_1() && sbi_probe_extension(SBI_EXT_SUSP) > 0) {
>
> Random thought I had reading this, was that it'll be possible to have a
> firmware that implements SBI < 2.0 that provides the SUSP extension.
> FWIW, I don't think that that is problematic, but maybe I am missing
> something that would make it so.

Right, it shouldn't matter for SUSP. In fact, I sort of wish SBI was
extension probing only (no version checks), but Anup tells me that PMU
requires also checking the version to know which functions are available.

Thanks,
drew