Re: [PATCH 4.19.y] ata: libata: disallow dev-initiated LPM transitions to unsupported states

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Sep 28, 2023 at 05:54:26PM +0200, Niklas Cassel wrote:
> 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>
> Fixes: 1152b2617a6e ("libata: implement sata_link_scr_lpm() and make ata_dev_set_feature() global")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> (cherry picked from commit 24e0e61db3cb86a66824531989f1df80e0939f26)
> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
> ---
>  drivers/ata/ahci.c        |  9 +++++++++
>  drivers/ata/libata-core.c | 19 ++++++++++++++++---
>  include/linux/libata.h    |  4 ++++
>  3 files changed, 29 insertions(+), 3 deletions(-)

Both now queued up, thanks.

greg k-h