Re: [REGRESSION] libata: SATA LPM forcibly disabled on Intel Raptor Lake since Linux 6.14.

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

On 1/7/26 12:20, Niklas Cassel wrote:
> I think the problem is:
> 
> [    3.010059] ata8.00: ATA-11: ST16000NM000J-2TW103, SN06, max UDMA/133
> [    3.010079] ata7.00: ATA-11: ST16000NM000J-2TW103, SN06, max UDMA/133
> [    3.012748] ata6.00: ATAPI: PIONEER BD-RW  BDR-S12JX, 1.01, max UDMA/100
> [    3.012779] ata5.00: ATAPI: PIONEER BD-RW  BDR-S12JX, 1.01, max UDMA/100
> [    3.061873] ata8.00: Features: DIPM NCQ-sndrcv
> [    3.065319] ata7.00: Features: DIPM NCQ-sndrcv
> 
> The ST drives advertise support for DIPM, so these two ports should enter
> a lower power state.
> 
> 
> For the PIONEER optical drives however, we don't seem to get any "Features: "
> print at all. My guess is that the support neither HIPM nor DIPM, and thus
> stops the whole system from entering a lower power state.
> 
> 
> What I think happens:
> 
> For a device that does not support HIPM, we will clear flag ATA_LPM_HIPM from
> hints:
> https://github.com/torvalds/linux/blob/v6.19-rc4/drivers/ata/libata-eh.c#L2168-L2169
> 
> If flag ATA_LPM_HIPM is not set, we will disable HIPM (ALPE) for the port:
> https://github.com/torvalds/linux/blob/v6.19-rc4/drivers/ata/libahci.c#L835-L847
> 
> Thus the HBA will never tell the device to enter a low power state.
> (And if DIPM is not supported, the device itself will never enter a low
> power state.)
> 
> 
> Questions:
> -Why was this not a problem on older kernels?
> 
> If you are willing try some patches from us, we could give you a patch with more
> debug prints, to show for each device, when we {enable,disable} {HIPM,DIPM}.
> 
> 
> -Why don't we get the Features: print for ATAPI devices?
> 
> We probably need something like this:

Before doing this, one simple test to do would be to unplug the 2 ATAPI devices
(CD/DVD drives) and reboot to see if LPM works then.

> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index fc250b494ce3..a8af200ac24f 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -3161,11 +3161,13 @@ int ata_dev_configure(struct ata_device *dev)
>                 /* print device info to dmesg */
>                 if (print_info)
>                         ata_dev_info(dev,
> -                                    "ATAPI: %s, %s, max %s%s%s%s\n",
> +                                    "ATAPI: %s, %s, max %s%s%s%s%s%s\n",
>                                      modelbuf, fwrevbuf,
>                                      ata_mode_string(xfer_mask),
>                                      cdb_intr_string, atapi_an_string,
> -                                    dma_dir_string);
> +                                    dma_dir_string,
> +                                    ata_id_has_hipm(dev->id) ? " HIPM" : "",
> +                                    ata_id_has_dipm(dev->id) ? " DIPM" : "");
>         }
>  
>         /* determine max_sectors */
> 
> 
> 
> Kind regards,
> Niklas


-- 
Damien Le Moal
Western Digital Research