On Fri, May 31, 2024 at 02:07:11PM +0200, Niklas Cassel wrote:
LPM consists of HIPM (host initiated power management) and DIPM (device initiated power management).
ata_eh_set_lpm() will only enable HIPM if both the HBA and the device supports it.
However, DIPM will be enabled as long as the device supports it. The HBA will later reject the device's request to enter a power state that it does not support (Slumber/Partial/DevSleep) (DevSleep is never initiated by the device).
For a HBA that doesn't support any LPM states, simply don't set a LPM policy such that all the HIPM/DIPM probing/enabling will be skipped.
Not enabling HIPM or DIPM in the first place is safer than relying on the device following the AHCI specification and respecting the NAK. (There are comments in the code that some devices misbehave when receiving a NAK.)
Performing this check in ahci_update_initial_lpm_policy() also has the advantage that a HBA that doesn't support any LPM states will take the exact same code paths as a port that is external/hot plug capable.
Fixes: 7627a0edef54 ("ata: ahci: Drop low power policy board type") Cc: stable@vger.kernel.org Signed-off-by: Niklas Cassel cassel@kernel.org
We have not received any bug reports with this. The devices that were quirked recently all supported both Partial and Slumber. This is more a defensive action, as it seems unnecessary to enable DIPM in the first place, if the HBA doesn't support any LPM states.
drivers/ata/ahci.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c index 07d66d2c5f0d..214de08de642 100644 --- a/drivers/ata/ahci.c +++ b/drivers/ata/ahci.c @@ -1735,6 +1735,12 @@ static void ahci_update_initial_lpm_policy(struct ata_port *ap) if (ap->pflags & ATA_PFLAG_EXTERNAL) return;
- /* If no LPM states are supported by the HBA, do not bother with LPM */
- if ((ap->host->flags & ATA_HOST_NO_PART) &&
(ap->host->flags & ATA_HOST_NO_SSC) &&(ap->host->flags & ATA_HOST_NO_DEVSLP))
For debugging purposes in case of potential issues, perhaps add a debug log here so it is visible that we don't enable LPM?
return;- /* user modified policy via module param */ if (mobile_lpm_policy != -1) { policy = mobile_lpm_policy;
-- 2.45.1