From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-ide@vger.kernel.org,
Linux ACPI <linux-acpi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mario Limonciello <mario.limonciello@amd.com>
Subject: Re: [PATCH v3] ata: ahci: Do not check ACPI_FADT_LOW_POWER_S0
Date: Fri, 26 Aug 2022 07:47:11 +0900 [thread overview]
Message-ID: <d8c72b2b-3962-786e-e87b-18be4b511637@opensource.wdc.com> (raw)
In-Reply-To: <12054041.O9o76ZdvQC@kreacher>
On 8/26/22 03:47, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> The ACPI_FADT_LOW_POWER_S0 flag merely means that it is better to
> use low-power S0 idle on the given platform than S3 (provided that
> the latter is supported) and it doesn't preclude using either of
> them (which of them will be used depends on the choices made by user
> space).
>
> For this reason, there is no benefit from checking that flag in
> ahci_update_initial_lpm_policy().
>
> First off, it cannot be a bug to do S3 with policy set to either
> ATA_LPM_MIN_POWER_WITH_PARTIAL or ATA_LPM_MIN_POWER, because S3 can be
> used on systems with ACPI_FADT_LOW_POWER_S0 set and it must work if
> really supported, so the ACPI_FADT_LOW_POWER_S0 check is not needed to
> protect the S3-capable systems from failing.
>
> Second, suspend-to-idle can be carried out on a system with
> ACPI_FADT_LOW_POWER_S0 unset and it is expected to work, so if setting
> policy to either ATA_LPM_MIN_POWER_WITH_PARTIAL or ATA_LPM_MIN_POWER is
> needed to handle that case correctly, it should be done regardless of
> the ACPI_FADT_LOW_POWER_S0 value.
>
> Accordingly, replace the ACPI_FADT_LOW_POWER_S0 check in
> ahci_update_initial_lpm_policy() with pm_suspend_default_s2idle()
> which is more general and also takes the user's preference into
> account and drop the CONFIG_ACPI #ifdef around it that is not necessary
> any more.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Applied to for-6.1. Thanks !
> ---
>
> v2 -> v3:
> * Use pm_suspend_default_s2idle() instead of the check being dropped.
> * Update the changelog.
>
> v1 -> v2:
> * Adjust subject (Damien).
> * Drop #ifdef CONFIG_ACPI that is not necessary any more (Mario).
> * Update the changelog.
>
> ---
> drivers/ata/ahci.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> Index: linux-pm/drivers/ata/ahci.c
> ===================================================================
> --- linux-pm.orig/drivers/ata/ahci.c
> +++ linux-pm/drivers/ata/ahci.c
> @@ -1609,15 +1609,12 @@ static void ahci_update_initial_lpm_poli
> goto update_policy;
> }
>
> -#ifdef CONFIG_ACPI
> - if (policy > ATA_LPM_MED_POWER &&
> - (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) {
> + if (policy > ATA_LPM_MED_POWER && pm_suspend_default_s2idle()) {
> if (hpriv->cap & HOST_CAP_PART)
> policy = ATA_LPM_MIN_POWER_WITH_PARTIAL;
> else if (hpriv->cap & HOST_CAP_SSC)
> policy = ATA_LPM_MIN_POWER;
> }
> -#endif
>
> update_policy:
> if (policy >= ATA_LPM_UNKNOWN && policy <= ATA_LPM_MIN_POWER)
>
>
>
--
Damien Le Moal
Western Digital Research
prev parent reply other threads:[~2022-08-25 22:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-25 18:47 [PATCH v3] ata: ahci: Do not check ACPI_FADT_LOW_POWER_S0 Rafael J. Wysocki
2022-08-25 18:48 ` Limonciello, Mario
2022-08-25 22:47 ` Damien Le Moal [this message]
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