Re: [PATCH] ata: libata: disallow dev-initiated LPM transitions to unsupported states

[Niklas Cassel <Niklas.Cassel@wdc.com>]

On Tue, Sep 05, 2023 at 11:29:13AM +0900, Damien Le Moal wrote:
> On 9/5/23 05:42, Niklas Cassel wrote:
> > From: Niklas Cassel <niklas.cassel@wdc.com>
> > 
> > In AHCI 1.3.1, the register description for CAP.SSC:
> > "When cleared to ‘0’, software must not allow the HBA to initiate
> > transitions to the Slumber state via agressive link power management nor
> > the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
> > must be programmed to disallow device initiated Slumber requests."
> > 
> > In AHCI 1.3.1, the register description for CAP.PSC:
> > "When cleared to ‘0’, software must not allow the HBA to initiate
> > transitions to the Partial state via agressive link power management nor
> > the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
> > must be programmed to disallow device initiated Partial requests."
> > 
> > Ensure that we always set the corresponding bits in PxSCTL.IPM, such that
> > a device is not allowed to initiate transitions to power states which are
> > unsupported by the HBA.
> > 
> > DevSleep is always initiated by the HBA, however, for completeness, set the
> > corresponding bit in PxSCTL.IPM such that agressive link power management
> > cannot transition to DevSleep if DevSleep is not supported.
> > 
> > sata_link_scr_lpm() is used by libahci, ata_piix and libata-pmp.
> > However, only libahci has the ability to read the CAP/CAP2 register to see
> > if these features are supported. Therefore, in order to not introduce any
> > regressions on ata_piix or libata-pmp, create flags that indicate that the
> > respective feature is NOT supported. This way, the behavior for ata_piix
> > and libata-pmp should remain unchanged.
> > 
> > This change is based on a patch originally submitted by Runa Guo-oc.
> > 
> > Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
> 
> Looks good, but don't we need a Fixes tag for this ?

Sure

Fixes: 1152b2617a6e ("libata: implement sata_link_scr_lpm() and make ata_dev_set_feature() global")

Can you add when applying, or do you want me to resend?


Kind regards,
Niklas