Re: [PATCH] ata: ahci: print the lpm policy on boot

[Hannes Reinecke <hare@suse.de>]

On 9/5/23 14:49, Niklas Cassel wrote:
> From: Niklas Cassel <niklas.cassel@wdc.com>
> 
> The target LPM policy can be set using either a Kconfig or a kernel module
> parameter.
> 
> However, if the board type is set to anything but board_ahci_low_power,
> then the LPM policy will overridden and set to ATA_LPM_UNKNOWN.
> 
> Additionally, if the default suspend is suspend to idle, depending on the
> hardware capabilities of the HBA, ahci_update_initial_lpm_policy() might
> override the LPM policy to either ATA_LPM_MIN_POWER_WITH_PARTIAL or
> ATA_LPM_MIN_POWER.
> 
> All this means that it is very hard to know which LPM policy a user will
> actually be using on a given system.
> 
> In order to make it easier to debug LPM related issues, print the LPM
> policy on boot.
> 
> One common LPM related issue is that the device fails to link up.
> Because of that, we cannot add this print to ata_dev_configure(), as that
> function is only called after a successful link up. Instead, add the info
> using ata_port_desc(). The port description is printed once during boot.
> 
> Before changes:
> ata1: SATA max UDMA/133 abar m524288@0xa5780000 port 0xa5780100 irq 170
> ata2: SATA max UDMA/133 abar m524288@0xa5780000 port 0xa5780180 irq 170
> 
> After changes:
> ata1: SATA max UDMA/133 abar m524288@0xa5780000 port 0xa5780100 lpm-pol 4 irq 170
> ata2: SATA max UDMA/133 abar m524288@0xa5780000 port 0xa5780180 lpm-pol 4 irq 170
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
> ---
>   drivers/ata/ahci.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index abb5911c9d09..541f6ec7f395 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1898,6 +1898,7 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>   			ap->em_message_type = hpriv->em_msg_type;
>   
>   		ahci_update_initial_lpm_policy(ap, hpriv);
> +		ata_port_desc(ap, "lpm-pol %d", ap->target_lpm_policy);
>   
>   		/* disabled/not-implemented port */
>   		if (!(hpriv->port_map & (1 << i)))

Hmm. Not very instructive ('pol 4' ?).
Please use a string mapping here to translate it into something 
human-readable.
Also one might consider a sysfs attribute to retrieve the information
from userspace.

Cheers,

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