linux-kernel - RE: [PATCH v2 2/2] ata: ahci: Protect users from setting policies their drives don't support

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Date:   Mon, 4 Apr 2022 23:53:20 +0000
From:   "Limonciello, Mario" <Mario.Limonciello@....com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
CC:     "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
        <linux-ide@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>
Subject: RE: [PATCH v2 2/2] ata: ahci: Protect users from setting policies
 their drives don't support

[AMD Official Use Only]



> -----Original Message-----
> From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
> Sent: Monday, April 4, 2022 18:31
> To: Limonciello, Mario <Mario.Limonciello@....com>
> Cc: open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers) <linux-
> ide@...r.kernel.org>; open list <linux-kernel@...r.kernel.org>;
> hdegoede@...hat.com
> Subject: Re: [PATCH v2 2/2] ata: ahci: Protect users from setting policies their
> drives don't support
> 
> On 4/5/22 04:39, Limonciello, Mario wrote:
> > [AMD Official Use Only]
> >
> >
> >
> >> -----Original Message-----
> >> From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
> >> Sent: Sunday, April 3, 2022 20:11
> >> To: Limonciello, Mario <Mario.Limonciello@....com>
> >> Cc: open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers) <linux-
> >> ide@...r.kernel.org>; open list <linux-kernel@...r.kernel.org>;
> >> hdegoede@...hat.com
> >> Subject: Re: [PATCH v2 2/2] ata: ahci: Protect users from setting policies
> their
> >> drives don't support
> >>
> >> On 3/3/22 12:49, 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 policies
> >>> dependent upon slumber (`min_power` or `min_power_with_partial`)
> affect
> >> the
> >>> disk.
> >>>
> >>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >>
> >> Mario,
> >>
> >> Can you resend a rebased version of this, on top of libata for-5.19 branch
> ?
> >
> >
> > OK.
> >
> >>
> >>> ---
> >>> Changes from v1->v2:
> >>> * Move deeper into codepaths
> >>> * Reset to MED_POWER rather than ignore
> >>>   drivers/ata/libata-sata.c | 11 +++++++++++
> >>>   1 file changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> >>> index 071158c0c44c..0dc03888c62b 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 +369,20 @@ 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;
> >>>   	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)) {
> >>> +		dev_warn(ap->host->dev,
> >>> +			"This drive doesn't support slumber; restting policy to
> >> MED_POWER\n");
> >>
> >> Typo here: s/restting/resetting. Also, s/doesn't/does not.
> >>
> >>> +		policy = ATA_LPM_MED_POWER;
> >>
> >> Here, shouldn't we use the default policy defined by
> >> CONFIG_SATA_LPM_POLICY ?
> >
> > If they set it too aggressively we still don't want to honor it if the drive
> > can't do slumber I would expect.
> 
> True. But if the default is set to a higher performance mode, we should
> not fall back to the med-power mode.
> 
> We should either (1) fallback to the closest higher performance policy
> supported, or (2) not change the current policy at all. no ?
> 
> See what ahci_update_initial_lpm_policy() does to check the possible
> "initial" (the default ?) policy.

OK - take a look what I did in the resubmission:
https://lore.kernel.org/all/20220404194510.9206-2-mario.limonciello@amd.com/

> 
> 
> 
> >
> >>
> >>> +	}
> >>> +
> >>>   	rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
> >>>   	if (rc)
> >>>   		return rc;
> >>
> >>
> >> --
> >> Damien Le Moal
> >> Western Digital Research
> 
> 
> --
> Damien Le Moal
> Western Digital Research