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

From: Conor Dooley <conor@kernel.org>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: linux-riscv@lists.infradead.org, paul.walmsley@sifive.com,
	palmer@dabbelt.com, aou@eecs.berkeley.edu,
	leyfoon.tan@starfivetech.com, jeeheng.sia@starfivetech.com,
	conor.dooley@microchip.com, apatel@ventanamicro.com
Subject: Re: [PATCH v1 1/1] riscv: sbi: Introduce system suspend support
Date: Thu, 12 Oct 2023 14:32:46 +0100	[thread overview]
Message-ID: <20231012-pulverize-founding-f459336028a2@spud> (raw)
In-Reply-To: <20231012-powdery-demeanor-4d8dde576f24@spud>

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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.

Hmm, next patch I look at is from Anup's debug console series, and he
does check that the SBI implementation is at least version 2.0 before
probing for the extension. We should probably have the same policy
everywhere.

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