Hi,
On 27-04-18 11:07, Alan Jenkins wrote:
On 27/04/18 09:36, Hans de Goede wrote:
Hi,
On 27-04-18 10:33, Alan Jenkins wrote:
On 29/03/18 12:06, Hans de Goede wrote:
Hi,
On 29-03-18 12:53, Alan Jenkins wrote:
My laptop LPM status, even after removing AC power:
$ head /sys/class/scsi_host/host*/link_power_management_policy
==> /sys/class/scsi_host/host0/link_power_management_policy <==
max_performance
==> /sys/class/scsi_host/host1/link_power_management_policy <==
max_performance
Right, because all the bugs you linked indicate you are on
Fedora 27 and Fedora 27 does not have the LPM changes, of you
did have the LPM changes you would get something other then
max_performance for the lpm policy.
So whatever problem you are seeing, it is not related to the
SATA LPM changes.
Regards,
Hans
Thanks your help ruling out ALPM. I see the commit message in v4.15 was quite clear.
In v4.16 I read the new Kconfig, it looks the default for laptops has changed to preserve the LPM value set by firmware. And that this default is carried into Fedora 27 now.
$ grep MOBILE /boot/config-4.16.3-200.fc27.x86_64
CONFIG_SATA_MOBILE_LPM_POLICY=0
+ help
+ Select the Default SATA Link Power Management (LPM) policy to use
+ for mobile / laptop variants of chipsets / "South Bridges".
+
+ The value set has the following meanings:
+ 0 => Keep firmware settings
But the code doesn't seem to match. In `enum ata_lpm_policy`, 0 is ATA_LPM_UNKNOWN (and there is no FIRMWARE value at all). I cannot write "firmware" as an LPM value. And booting this Fedora kernel, reading the LPM value still shows "max_performance".
Can the Kconfig help text be clarified?
The Kconfig help-text is correct, a setting of 0 / ATA_LPM_UNKNOWN causes the libata code
to not make any changes to LPM settings, so it preserves whatever the firmware set.
But the sysfs interface has never known about this and always reported the ATA_LPM_UNKNOWN
setting (which has been the default for basically ever) as "max_performance".
So the Kconfig help-text is correct (to the best of my knowledge) but indeed when
compared to the sysfs value it is a bit confusing.
Regards,
Hans
Hi
Odd, that's not what I understood from Matthew Garret's 2015 posts, and I assume you wouldn't count some post-2015 change as "forever".
> In fact, right now we even remove any existing SATA power management configuration that the firmware has initialised.
- https://mjg59.dreamwidth.org/34868.html
His patches had to add code to save the firmware settings, as well as adding a new "firmware_default" policy (oops, not "firmware").
- https://lkml.org/lkml/2015/4/18/76
The code changing the LPM settings is guarded by this check:
if (link->lpm_policy != ap->target_lpm_policy)
Where link->lpm_policy always gets initialized to ATA_LPM_UNKNOWN
and ap->target_lpm_policy gets set to the Kconfig default (*) or
the value written to sysfs.
So when the policy is set to ATA_LPM_UNKNOWN we are not making
any changes, but it could be that we are doing a reset somewhere
which override the firmware values and replace them with the
por (power-on-reset) default values.
So maybe we should change the Kconfig help for 0 from
"Keep firmware settings" to "Default"?
Regards,
Hans
*) The Kconfig default only applies to chipsets which are marked as
"mobile", so this should only be used on laptops and some HTPC-ish
boxes which use a mobile chipset.
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