linux-kernel - Re: [RFC PATCH v2 1/2] ata: ahci: Support state with min power and Partial low power state

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Message-ID: <fa324b27-4424-afa2-9723-10437ca29801@redhat.com>
Date:   Fri, 13 Jul 2018 11:08:16 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        tj@...nel.org
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
        alan.cox@...el.com, Mario.Limonciello@...l.com, rjw@...ysocki.net
Subject: Re: [RFC PATCH v2 1/2] ata: ahci: Support state with min power and
 Partial low power state

Hi,

On 13-07-18 00:27, Srinivas Pandruvada wrote:
> Currently when min_power policy is selected, the partial low power state
> is not entered and link will try aggressively enter to only slumber state.
> Add a new policy which still enable DEVSLP but also try to enter partial
> low power state.
> 
> For information the difference between partial and slumber
> Partial – PHY logic is powered up, and in a reduced power state. The link
> PM exit latency to active state maximum is 10 ns.
> Slumber – PHY logic is powered up, and in a reduced power state. The link
> PM exit latency to active state maximum is 10 ms.
> Devslp – PHY logic is powered down. The link PM exit latency from this
> state to active state maximum is 20 ms, unless otherwise specified by
> DETO.
> 
> Suggested-by: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

You got this the wrong way around, when ALP is not set you only get
partial, the ALP bit is active high, not active low as your commit
suggests.  So the name of the new policy should be min_power_without_asp.

Regards,

Hans






> ---
>   drivers/ata/libahci.c     | 6 +++++-
>   drivers/ata/libata-core.c | 1 +
>   drivers/ata/libata-scsi.c | 1 +
>   include/linux/libata.h    | 3 ++-
>   4 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index 511fb67f363d..8cf2cf49537d 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -799,8 +799,11 @@ static int ahci_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
>   				return 0;
>   		} else {
>   			cmd |= PORT_CMD_ALPE;
> +
>   			if (policy == ATA_LPM_MIN_POWER)
>   				cmd |= PORT_CMD_ASP;
> +			else if (policy == ATA_LPM_MIN_POWER_WITH_ASP)
> +				cmd &= ~PORT_CMD_ASP;
>   
>   			/* write out new cmd value */
>   			writel(cmd, port_mmio + PORT_CMD);
> @@ -811,7 +814,8 @@ static int ahci_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
>   	if ((hpriv->cap2 & HOST_CAP2_SDS) &&
>   	    (hpriv->cap2 & HOST_CAP2_SADM) &&
>   	    (link->device->flags & ATA_DFLAG_DEVSLP)) {
> -		if (policy == ATA_LPM_MIN_POWER)
> +		if (policy == ATA_LPM_MIN_POWER ||
> +		    policy == ATA_LPM_MIN_POWER_WITH_ASP)
>   			ahci_set_aggressive_devslp(ap, true);
>   		else
>   			ahci_set_aggressive_devslp(ap, false);
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index cc71c63df381..245a59e6cb18 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -3970,6 +3970,7 @@ int sata_link_scr_lpm(struct ata_link *link, enum ata_lpm_policy policy,
>   		scontrol |= (0x6 << 8);
>   		break;
>   	case ATA_LPM_MED_POWER_WITH_DIPM:
> +	case ATA_LPM_MIN_POWER_WITH_ASP:
>   	case ATA_LPM_MIN_POWER:
>   		if (ata_link_nr_enabled(link) > 0)
>   			/* no restrictions on LPM transitions */
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index aad1b01447de..2d683db50ceb 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -110,6 +110,7 @@ static const char *ata_lpm_policy_names[] = {
>   	[ATA_LPM_MAX_POWER]		= "max_performance",
>   	[ATA_LPM_MED_POWER]		= "medium_power",
>   	[ATA_LPM_MED_POWER_WITH_DIPM]	= "med_power_with_dipm",
> +	[ATA_LPM_MIN_POWER_WITH_ASP]	= "min_power_with_asp",
>   	[ATA_LPM_MIN_POWER]		= "min_power",
>   };
>   
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 32f247cb5e9e..1e154f1f7e8f 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -523,7 +523,8 @@ enum ata_lpm_policy {
>   	ATA_LPM_MAX_POWER,
>   	ATA_LPM_MED_POWER,
>   	ATA_LPM_MED_POWER_WITH_DIPM, /* Med power + DIPM as win IRST does */
> -	ATA_LPM_MIN_POWER,
> +	ATA_LPM_MIN_POWER_WITH_ASP, /* Min Power + partial and slumber */
> +	ATA_LPM_MIN_POWER, /* Min power + no partial (slumber only) */
>   };
>   
>   enum ata_lpm_hints {
>