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

Thu, 19 Jul 2018 06:14:36 -0700 

Hi,

On 13-07-18 17:06, Srinivas Pandruvada wrote:

Hi Hans,
On Fri, 2018-07-13 at 11:08 +0200, Hans de Goede wrote:

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 <[email protected]>
Signed-off-by: Srinivas Pandruvada <[email protected]
.com>


You got this the wrong way around, when ALP

You mean ASP, as per spec in section 3.3.7 of the spec.


  is not set you only get
partial,

Not exactly.
It means that the system will try to enter aggressively  partial . I
have seen slumber residency also when this is reset. When "set" you
don't see any any partial. But when you reset you see both. So based on
idle duration link will transition from partial to slumber even if "not
set".


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.



The policy name I am suggesting is not the actual bit value of ASP (I
interpreted ASP as name for partial), but whether you will get to
partial or not. So I think it is better to rename to
"min_power_with_partial". User should not have to worry about the bit
value.


So user will see with the rename from "min_power_with_asp" to
"min_power_with_partial":

#cat /sys/class/scsi_host/host*/link_power_management_policy
min_power_with_partial
min_power_with_partial
min_power_with_partial

Output of test (You will see both partial and slumber)

SATA LPM Summary - Sampled: Residency (Percentage)
Disk Name          , Off (%), Active (%), Partial (%), Slumber (%), Devsleep 
(%), Other (%), Uninitialized (%)
---------          , -------, ----------, -----------, -----------, 
------------, ---------, -----------------
INTEL SSDSCKJF180A5, 0.0    , 4.6       , 13.1       , 30.3       , 52.0        
, 0.0      , 0.0

SATA LPM Summary - Sampled: Counts
Disk Name          , Off, Active, Partial, Slumber, Devsleep, Other, 
Uninitialized
---------          , ---, ------, -------, -------, --------, -----, 
-------------
INTEL SSDSCKJF180A5, 0  , 9     , 27     , 60     , 103     , 0    , 0


# cat /sys/class/scsi_host/host*/link_power_management_policy
min_power
min_power
min_power

Output of test (You will see only slumber)

SATA LPM Summary - Sampled: Residency (Percentage)
Disk Name          , Off (%), Active (%), Partial (%), Slumber (%), Devsleep 
(%), Other (%), Uninitialized (%)
---------          , -------, ----------, -----------, -----------, 
------------, ---------, -----------------
INTEL SSDSCKJF180A5, 0.0    , 6.8       , 0.0        , 53.8       , 39.3        
, 0.0      , 0.0

SATA LPM Summary - Sampled: Counts
Disk Name          , Off, Active, Partial, Slumber, Devsleep, Other, 
Uninitialized
---------          , ---, ------, -------, -------, --------, -----, 
-------------
INTEL SSDSCKJF180A5, 0  , 11    , 0      , 107    , 76      , 0    , 0


Ah, I see thank you for clarifying that. Yes I agree that
min_power_with_partial is the best name for the new policy.

For the next version do not forget to make the overriding of the
lpm policy a per host thing, rather then directly overriding the
global value as I mentioned in a previous mail.

One other thing is to NOT override the policy if it is set on
the kernel-commandline, which I believe will require setting the
global value to -1 and only set another value if the global value
is not -1 (using you settings where applicable and falling back
to CONFIG_SATA_MOBILE_LPM_POLICY where not applicable).

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 {

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