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

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Date:   Thu, 3 Mar 2022 11:52:02 +0200
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Mario Limonciello <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 2022/03/03 5:49, 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>
> ---
> 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)) {

Weird indentation.

> +		dev_warn(ap->host->dev,
> +			"This drive doesn't support slumber; restting policy to MED_POWER\n");

Typo. I would change this to:

"This device does not support slumber; defaulting to MED_POWER policy\n"

> +		policy = ATA_LPM_MED_POWER;
> +	}
> +
>  	rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
>  	if (rc)
>  		return rc;


-- 
Damien Le Moal
Western Digital Research