Re: [PATCH v3 2/2] ata: ahci: Protect users from setting policies their drives don't support

[Damien Le Moal]

On 4/6/22 11:24, Damien Le Moal wrote:
> On 4/5/22 04:45, Mario Limonciello wrote:
> > As the default low power policy applies to more chipsets and drives, it's
> > important to make sure that drives actually support the policy that a 
> > user
> > selected in their kernel configuration.
> >
> > If the drive doesn't support slumber, don't let the default policy for 
> > the
> > ATA port be `min_power` or `min_power_with_partial`.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> > v2->v3:
> >   * Fix typo
> >   * Try to reset to CONFIG_SATA_LPM_POLICY unless that's too aggressive
> >     then take MED_POWER.
> >   drivers/ata/libata-sata.c | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> > index 044a16daa2d4..b41de7e03dce 100644
> > --- a/drivers/ata/libata-sata.c
> > +++ b/drivers/ata/libata-sata.c
> > @@ -13,6 +13,7 @@
> >   #include <scsi/scsi_device.h>
> >   #include <linux/libata.h>
> > +#include "ahci.h"
> >   #include "libata.h"
> >   #include "libata-transport.h"
> > @@ -368,10 +369,21 @@ int sata_link_scr_lpm(struct ata_link *link, 
> > enum ata_lpm_policy policy,
> >                 bool spm_wakeup)
> >   {
> >       struct ata_eh_context *ehc = &link->eh_context;
> > +    struct ata_port *ap = link->ap;
> > +    struct ahci_host_priv *hpriv;
>
> That does not work. This function is used by the ata_piix driver too, 
> which is not ahci...
>
> >       bool woken_up = false;
> >       u32 scontrol;
> >       int rc;
> > +    hpriv = ap->host->private_data;
> > +    if (policy >= ATA_LPM_MIN_POWER_WITH_PARTIAL &&
> > +      !(hpriv->cap & HOST_CAP_SSC)) {
>
> ...which mean that this flag needs to be moved to struct ata_host to 
> keep this function generic for different LLDDs.

Here I meant having a ata_host flag equivalent, indicating the adapter 
supports slumber state.

> > +        policy = (CONFIG_SATA_LPM_POLICY < 
> > ATA_LPM_MIN_POWER_WITH_PARTIAL) ?
> > +             CONFIG_SATA_LPM_POLICY : ATA_LPM_MED_POWER;
>
> I really prefer an explicit "if () else" for readability.
> Also, please revert here to CONFIG_SATA_MOBILE_LPM_POLICY.
>
> > +        dev_warn(ap->host->dev,
> > +            "This drive doesn't support slumber; resetting policy to 
> > %d\n", policy);
>
> s/doesn't/does not
>
> > +    }
> > +
> >       rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
> >       if (rc)
> >           return rc;
>
> Also, as patch 3 of this series, can you add the patch that changes 
> CONFIG_SATA_MOBILE_LPM_POLICY to being "3" by default ?
>
> And please use a cover letter when you have more than 1 patch. The 
> change log can then be in the cover letter instead of in each patch.


--
Damien Le Moal
Western Digital Research