Re: [PATCH 08/10] ata: ahci: Disallow LPM policy control if not supported

[Hannes Reinecke <hare@suse.de>]

On 6/30/25 08:26, Damien Le Moal wrote:
> Commit fa997b0576c9 ("ata: ahci: Do not enable LPM if no LPM states are
> supported by the HBA") introduced an early return in
> ahci_update_initial_lpm_policy() to ensure that the target_lpm_policy
> of ports belonging to a host that does not support the Partial, Slumber
> and DevSleep power states is unchanged and remains set to
> ATA_LPM_UNKNOWN and thus prevents the execution of
> ata_eh_link_set_lpm().
> 
> However, a user or a system daemon (e.g. systemd-udevd) may still
> attempt changing the LPM policy through the sysfs
> link_power_management_policy of the host.
> 
> Improve this to prevent sysfs LPM policy changes by setting the flag
> ATA_FLOAG_NO_LPM for the port of such host, and initialize the port
> target_lpm_policy to ATA_LPM_MAX_POWER to guarantee that no unsupported
> low power state is being used on the port and its link.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>   drivers/ata/ahci.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 34698ae39f55..737f5d1bde11 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1793,7 +1793,10 @@ static void ahci_update_initial_lpm_policy(struct ata_port *ap)
>   	if ((ap->host->flags & ATA_HOST_NO_PART) &&
>   	    (ap->host->flags & ATA_HOST_NO_SSC) &&
>   	    (ap->host->flags & ATA_HOST_NO_DEVSLP)) {
> -		ata_port_dbg(ap, "no LPM states supported, not enabling LPM\n");
> +		ata_port_warn(ap,
> +			"No LPM states supported, forcing LPM max_power\n");
> +		ap->flags |= ATA_FLAG_NO_LPM;
> +		ap->target_lpm_policy = ATA_LPM_MAX_POWER;
>   		return;
>   	}
>   

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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