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

[Damien Le Moal <dlemoal@kernel.org>]

On 9/5/23 21:49, 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

Looks good, but maybe print the lpm-pol value at the end, after the IRQ number,
to preserve the beginning of the message as it was before.

Or even better: why not print the LPM modes supported by the port and the target
lpm policy (lpm-pol) as a new ata_port_info() message right after the port desc
message ?

> 
> 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)))

-- 
Damien Le Moal
Western Digital Research