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

From: Paul Menzel
Date: Mon Dec 27 2021 - 11:28:00 EST

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@xxxxxxxxxxxxx>
Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>

---
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.

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 */
--
2.30.2