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Message-ID: <CAJZ5v0hauoY0xDJqDUQwbY3kz6o7irELtvbYs+ruyMu_MYQzdw@mail.gmail.com>
Date: Mon, 29 Aug 2022 16:40:01 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Limonciello, Mario" <mario.limonciello@....com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <lenb@...nel.org>, Pavel Machek <pavel@....cz>,
Hans de Goede <hdegoede@...hat.com>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops
On Mon, Aug 29, 2022 at 4:32 PM Limonciello, Mario
<mario.limonciello@....com> wrote:
>
> On 8/29/2022 09:20, Rafael J. Wysocki wrote:
> > On Mon, Aug 29, 2022 at 3:29 PM Mario Limonciello
> > <mario.limonciello@....com> wrote:
> >>
> >> On some platforms it is found that Linux more aggressively enters s2idle
> >> than Windows enters Modern Standby and this uncovers some synchronization
> >> issues for the platform. To aid in debugging this class of problems in
> >> the future, add support for an extra optional callback intended for
> >> drivers to emit extra debugging.
> >
> > I'm not liking this.
> >
> > If you want debug, why not simply add it where it is needed?
>
> Actually this is exactly where it's needed. The synchronization issue
> is with what non-x86 is doing while x86 transitions into ACPI C3.
I meant directly, without adding new driver callbacks. Adding
callbacks for debug only seems a bit excessive.
But I guess the problem is that you need to ask the PMC about
something then, don't you?
> >
> >> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >> ---
> >> v1->v2:
> >> * Add a prototype for `acpi_s2idle_enter`
> >>
> >> drivers/acpi/sleep.h | 1 +
> >> drivers/acpi/x86/s2idle.c | 14 ++++++++++++++
> >> include/linux/acpi.h | 1 +
> >> include/linux/suspend.h | 1 +
> >> kernel/power/suspend.c | 3 +++
> >> 5 files changed, 20 insertions(+)
> >>
> >> diff --git a/drivers/acpi/sleep.h b/drivers/acpi/sleep.h
> >> index 7fe41ee489d6..7856930a7da9 100644
> >> --- a/drivers/acpi/sleep.h
> >> +++ b/drivers/acpi/sleep.h
> >> @@ -18,6 +18,7 @@ static inline acpi_status acpi_set_waking_vector(u32 wakeup_address)
> >> extern int acpi_s2idle_begin(void);
> >> extern int acpi_s2idle_prepare(void);
> >> extern int acpi_s2idle_prepare_late(void);
> >> +extern void acpi_s2idle_enter(void);
> >
> > And this name is confusing, because it suggests that the role of the
> > callback is to make the platform enter s2idle which isn't the case.
>
> Can you propose another name?
acpi_s2idle_check() or similar.
> >
> >> extern bool acpi_s2idle_wake(void);
> >> extern void acpi_s2idle_restore_early(void);
> >> extern void acpi_s2idle_restore(void);
> >> diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
> >> index f9ac12b778e6..c984093a3657 100644
> >> --- a/drivers/acpi/x86/s2idle.c
> >> +++ b/drivers/acpi/x86/s2idle.c
> >> @@ -486,6 +486,19 @@ int acpi_s2idle_prepare_late(void)
> >> return 0;
> >> }
> >>
> >> +void acpi_s2idle_enter(void)
> >> +{
> >> + struct acpi_s2idle_dev_ops *handler;
> >> +
> >> + if (!lps0_device_handle || sleep_no_lps0)
> >> + return;
> >> +
> >> + list_for_each_entry(handler, &lps0_s2idle_devops_head, list_node) {
> >> + if (handler->enter)
> >> + handler->enter();
> >> + }
> >> +}
> >> +
> >> void acpi_s2idle_restore_early(void)
> >> {
> >> struct acpi_s2idle_dev_ops *handler;
> >> @@ -527,6 +540,7 @@ static const struct platform_s2idle_ops acpi_s2idle_ops_lps0 = {
> >> .begin = acpi_s2idle_begin,
> >> .prepare = acpi_s2idle_prepare,
> >> .prepare_late = acpi_s2idle_prepare_late,
> >> + .enter = acpi_s2idle_enter,
> >> .wake = acpi_s2idle_wake,
> >> .restore_early = acpi_s2idle_restore_early,
> >> .restore = acpi_s2idle_restore,
> >> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> >> index 6f64b2f3dc54..9df14b5a875c 100644
> >> --- a/include/linux/acpi.h
> >> +++ b/include/linux/acpi.h
> >> @@ -1076,6 +1076,7 @@ struct acpi_s2idle_dev_ops {
> >> struct list_head list_node;
> >> void (*prepare)(void);
> >> void (*restore)(void);
> >> + void (*enter)(void);
> >> };
> >> int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg);
> >> void acpi_unregister_lps0_dev(struct acpi_s2idle_dev_ops *arg);
> >> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> >> index 70f2921e2e70..5a3fdca0a628 100644
> >> --- a/include/linux/suspend.h
> >> +++ b/include/linux/suspend.h
> >> @@ -191,6 +191,7 @@ struct platform_s2idle_ops {
> >> int (*begin)(void);
> >> int (*prepare)(void);
> >> int (*prepare_late)(void);
> >> + void (*enter)(void);
> >> bool (*wake)(void);
> >> void (*restore_early)(void);
> >> void (*restore)(void);
> >> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> >> index 827075944d28..0c08032d6b50 100644
> >> --- a/kernel/power/suspend.c
> >> +++ b/kernel/power/suspend.c
> >> @@ -136,6 +136,9 @@ static void s2idle_loop(void)
> >> break;
> >> }
> >>
> >> + if (s2idle_ops && s2idle_ops->enter)
> >> + s2idle_ops->enter();
> >> +
> >> s2idle_enter();
> >> }
> >>
> >> --
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