On 2/24/22 23:34, Paul Menzel wrote:
[...]
>> Thank you for cooking this up. I tested this on the ASUS F2A85-M PRO
>> (AMD, 1022:0x7801), MSI B350M MORTAR (AMD, 1022:0x7901), and IBM S822LC
>> (Marvell, 1b4b:9235) with no issues and the expected decrease in boot time.
>
> There is still one issue I noticed. The MSI B350M MORTAR has nine(?)
> SATA ports, and only one is connected to an SSD. For some of the other
> unpopulated ports a delay of 100 ms happens (although in Linux kernel
> threads, but still in serial and not parallel). Unfortunately, that
> system uses LUKS encryption, and as things are happening in initrd, I do
> not know if the delays would hold up the overall boot. I need to do more
> tests.
>
> ```
> $ grep sata_link_hardreset 20220220-sata-hardreset.txt
> 0.706289 | 0) scsi_eh-70 | |
> sata_link_hardreset() {
> 0.718497 | 0) scsi_eh-92 | |
> sata_link_hardreset() {
> 0.728425 | 0) scsi_eh-92 | # 9927.978 us | } /*
> sata_link_hardreset */
> 0.811159 | 2) scsi_eh-70 | @ 104870.3 us | } /*
> sata_link_hardreset */
> 0.811329 | 2) scsi_eh-72 | |
> sata_link_hardreset() {
> 0.920672 | 3) scsi_eh-72 | @ 109343.5 us | } /*
> sata_link_hardreset */
> 0.920915 | 2) scsi_eh-78 | |
> sata_link_hardreset() {
> 1.024618 | 2) scsi_eh-78 | @ 103703.7 us | } /*
> sata_link_hardreset */
> 1.025027 | 0) scsi_eh-80 | |
> sata_link_hardreset() {
> 1.128589 | 0) scsi_eh-80 | @ 103561.6 us | } /*
> sata_link_hardreset */
> ```
This looks like the delay for the link stability check in
sata_link_debounce(). 100ms is added (more for hotplug case) to ensure
that the SStatus register DET field provides a stable value.
As mentioned in another email on this subject, I cannot find any text in
the AHCI and SATA IO specs that mandate such large delay. Still need to
dig the history of this delay and why it was added.
--
Damien Le Moal
Western Digital Research
