Re: [PATCH v2 3/3] ahci: AMD A85 FCH (Hudson D4): Skip 200 ms debounce delay in `sata_link_resume()`

[Paul Menzel <pmenzel@molgen.mpg.de>]

Dear Linux folks,


Am 27.12.21 um 17:26 schrieb Paul Menzel:
> Since the first commit 1da177e4c3 (Linux-2.6.12-rc2) in the Linux git
> repository, `sata_link_resume()` contains a 200 ms delay with the comment
> below.
> 
>>     /*
>>      * Some PHYs react badly if SStatus is pounded
>>      * immediately after resuming.  Delay 200ms before
>>      * debouncing.
>>      */
> 
> A lot of PHYs do not have that problem though, so delaying 200 ms increases
> the boot time by 30 percent unnecessarily for a lot of systems, making
> “instant booting” quite hard.
> 
> As it’s unknown for what PHY the delay was added, create a new board
> `board_ahci_nodbdelay` with the link flag `ATA_LFLAG_NO_DB_DELAY,`, and,
> for now, configure the AMD A85 FCH (Hudson D4) to use it.
> 
> On the ASUS F2A85-M PRO it reduces the Linux kernel boot time by the
> expected 200 ms from 787 ms to 585 ms.
> 
> Tested on ASUS F2A85-M PRO:
> 
> Without patch, i. e., with 200 ms debounce delay:
> 
>      […]
>      [    0.000000] DMI: ASUS F2A85-M_PRO/F2A85-M_PRO, BIOS 4.15-671-g7b043ef855 12/27/2021
>      […]
>      [    0.404885] ahci 0000:00:11.0: version 3.0
>      [    0.405466] ahci 0000:00:11.0: AHCI 0001.0300 32 slots 8 ports 6 Gbps 0x40 impl SATA mode
>      [    0.405470] ahci 0000:00:11.0: flags: 64bit ncq sntf ilck led clo pio
>      [    0.408036] scsi host0: ahci
>      [    0.408537] scsi host1: ahci
>      [    0.408932] scsi host2: ahci
>      [    0.409444] scsi host3: ahci
>      [    0.409841] scsi host4: ahci
>      [    0.410266] scsi host5: ahci
>      [    0.410661] scsi host6: ahci
>      [    0.411052] scsi host7: ahci
>      [    0.411284] ata1: DUMMY
>      [    0.411286] ata2: DUMMY
>      [    0.411286] ata3: DUMMY
>      [    0.411287] ata4: DUMMY
>      [    0.411288] ata5: DUMMY
>      [    0.411289] ata6: DUMMY
>      [    0.411291] ata7: SATA max UDMA/133 abar m2048@0xf01cc000 port 0xf01cc400 irq 19
>      [    0.411292] ata8: DUMMY
>      […]
>      [    0.422362] Key type encrypted registered
>      [    0.424903] PM:   Magic number: 1:28:636
>      [    0.723979] ata7: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
>      [    0.724268] ata7.00: ATA-9: SanDisk SDSSDP064G, 2.0.0, max UDMA/133
>      [    0.724271] ata7.00: 125045424 sectors, multi 1: LBA48 NCQ (depth 32)
>      [    0.725537] ata7.00: configured for UDMA/133
>      [    0.725898] scsi 6:0:0:0: Direct-Access     ATA      SanDisk SDSSDP06 0    PQ: 0 ANSI: 5
>      [    0.726428] sd 6:0:0:0: [sda] 125045424 512-byte logical blocks: (64.0 GB/59.6 GiB)
>      [    0.726442] sd 6:0:0:0: [sda] Write Protect is off
>      [    0.726446] sd 6:0:0:0: [sda] Mode Sense: 00 3a 00 00
>      [    0.726464] sd 6:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
>      [    0.727985]  sda: sda1 sda2 sda3
>      [    0.728588] sd 6:0:0:0: [sda] Attached SCSI disk
>      [    0.738495] EXT4-fs (sda3): mounted filesystem with ordered data mode. Opts: (null). Quota mode: none.
>      […]
>      [    0.786812] Run /sbin/init as init process
> 
> With patch, i. e., skipping the debounce delay saves 200 ms from the boot
> as expected.
> 
>      […]
>      [    0.000000] DMI: ASUS F2A85-M_PRO/F2A85-M_PRO, BIOS 4.15-671-g7b043ef855 12/27/2021
>      […]
>      [    0.407372] ahci 0000:00:11.0: version 3.0
>      [    0.407909] ahci 0000:00:11.0: AHCI 0001.0300 32 slots 8 ports 6 Gbps 0x40 impl SATA mode
>      [    0.407913] ahci 0000:00:11.0: flags: 64bit ncq sntf ilck led clo pio
>      [    0.410520] scsi host0: ahci
>      [    0.411017] scsi host1: ahci
>      [    0.411418] scsi host2: ahci
>      [    0.411810] scsi host3: ahci
>      [    0.412225] scsi host4: ahci
>      [    0.412614] scsi host5: ahci
>      [    0.413005] scsi host6: ahci
>      [    0.413488] scsi host7: ahci
>      [    0.413713] ata1: DUMMY
>      [    0.413715] ata2: DUMMY
>      [    0.413716] ata3: DUMMY
>      [    0.413716] ata4: DUMMY
>      [    0.413717] ata5: DUMMY
>      [    0.413718] ata6: DUMMY
>      [    0.413720] ata7: SATA max UDMA/133 abar m2048@0xf01cc000 port 0xf01cc400 irq 19
>      [    0.413722] ata8: DUMMY
>      […]
>      [    0.425414] Key type encrypted registered
>      [    0.427873] PM:   Magic number: 1:234:838
>      [    0.522131] ata7: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
>      [    0.522415] ata7.00: ATA-9: SanDisk SDSSDP064G, 2.0.0, max UDMA/133
>      [    0.522418] ata7.00: 125045424 sectors, multi 1: LBA48 NCQ (depth 32)
>      [    0.523636] ata7.00: configured for UDMA/133
>      [    0.523993] scsi 6:0:0:0: Direct-Access     ATA      SanDisk SDSSDP06 0    PQ: 0 ANSI: 5
>      [    0.524497] sd 6:0:0:0: [sda] 125045424 512-byte logical blocks: (64.0 GB/59.6 GiB)
>      [    0.524511] sd 6:0:0:0: [sda] Write Protect is off
>      [    0.524515] sd 6:0:0:0: [sda] Mode Sense: 00 3a 00 00
>      [    0.524534] sd 6:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
>      [    0.525953]  sda: sda1 sda2 sda3
>      [    0.526541] sd 6:0:0:0: [sda] Attached SCSI disk
>      [    0.536245] EXT4-fs (sda3): mounted filesystem with ordered data mode. Opts: (null). Quota mode: none.
>      […]
>      [    0.585327] Run /sbin/init as init process
> 
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: Guenter Roeck <groeck@chromium.org>
> 
> ---
>   drivers/ata/ahci.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> v2: Add new board to enum `board_ids`.
> 
> Add the two Chromium OS developers Dmitry and Guenter to Cc, as to my
> knowledge Chromium/Chrome OS also tries to boot very fast, and the Chromium
> project has some CI infrastructure.

By the way, I do not even know what the PHY actually is, and how it can 
be checked.

Maybe the original commit message for the 200 ms delay mentions the PHY, 
but I have no idea how to access that history.

If the delay would be removed unconditionally, a module parameter would 
probably be a good idea, so people with bad PHY’s have an easy way to 
get it booting again.


Kind regards,

Paul


> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 6a2432e4adda..4f3e0603864d 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -51,6 +51,7 @@ enum board_ids {
>   	board_ahci,
>   	board_ahci_ign_iferr,
>   	board_ahci_mobile,
> +	board_ahci_nodbdelay,
>   	board_ahci_nomsi,
>   	board_ahci_noncq,
>   	board_ahci_nosntf,
> @@ -141,6 +142,13 @@ static const struct ata_port_info ahci_port_info[] = {
>   		.udma_mask	= ATA_UDMA6,
>   		.port_ops	= &ahci_ops,
>   	},
> +	[board_ahci_nodbdelay] = {
> +		.flags		= AHCI_FLAG_COMMON,
> +		.link_flags	= ATA_LFLAG_NO_DB_DELAY,
> +		.pio_mask	= ATA_PIO4,
> +		.udma_mask	= ATA_UDMA6,
> +		.port_ops	= &ahci_ops,
> +	},
>   	[board_ahci_nomsi] = {
>   		AHCI_HFLAGS	(AHCI_HFLAG_NO_MSI),
>   		.flags		= AHCI_FLAG_COMMON,
> @@ -437,6 +445,7 @@ static const struct pci_device_id ahci_pci_tbl[] = {
>   		board_ahci_al },
>   	/* AMD */
>   	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_HUDSON2_SATA_IDE), board_ahci },
> +	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_HUDSON2_SATA_AHCI), board_ahci_nodbdelay },
>   	{ PCI_VDEVICE(AMD, 0x7900), board_ahci }, /* AMD CZ */
>   	{ PCI_VDEVICE(AMD, 0x7901), board_ahci_mobile }, /* AMD Green Sardine */
>   	/* AMD is using RAID class only for ahci controllers */