On 9/13/23 19:34, Geert Uytterhoeven wrote: > Hi Damien, > > On Wed, Sep 13, 2023 at 12:21 PM Geert Uytterhoeven > <geert@xxxxxxxxxxxxxx> wrote: >> On Wed, Sep 13, 2023 at 12:58 AM Damien Le Moal <dlemoal@xxxxxxxxxx> wrote: >>> On 9/13/23 02:39, Geert Uytterhoeven wrote: >>>> On Mon, 31 Jul 2023, Damien Le Moal wrote: >>>>> During system resume, ata_port_pm_resume() triggers ata EH to >>>>> 1) Resume the controller >>>>> 2) Reset and rescan the ports >>>>> 3) Revalidate devices >>>>> This EH execution is started asynchronously from ata_port_pm_resume(), >>>>> which means that when sd_resume() is executed, none or only part of the >>>>> above processing may have been executed. However, sd_resume() issues a >>>>> START STOP UNIT to wake up the drive from sleep mode. This command is >>>>> translated to ATA with ata_scsi_start_stop_xlat() and issued to the >>>>> device. However, depending on the state of execution of the EH process >>>>> and revalidation triggerred by ata_port_pm_resume(), two things may >>>>> happen: >>>>> 1) The START STOP UNIT fails if it is received before the controller has >>>>> been reenabled at the beginning of the EH execution. This is visible >>>>> with error messages like: >>>>> >>>>> ata10.00: device reported invalid CHS sector 0 >>>>> sd 9:0:0:0: [sdc] Start/Stop Unit failed: Result: hostbyte=DID_OK driverbyte=DRIVER_OK >>>>> sd 9:0:0:0: [sdc] Sense Key : Illegal Request [current] >>>>> sd 9:0:0:0: [sdc] Add. Sense: Unaligned write command >>>>> sd 9:0:0:0: PM: dpm_run_callback(): scsi_bus_resume+0x0/0x90 returns -5 >>>>> sd 9:0:0:0: PM: failed to resume async: error -5 >>>>> >>>>> 2) The START STOP UNIT command is received while the EH process is >>>>> on-going, which mean that it is stopped and must wait for its >>>>> completion, at which point the command is rather useless as the drive >>>>> is already fully spun up already. This case results also in a >>>>> significant delay in sd_resume() which is observable by users as >>>>> the entire system resume completion is delayed. >>>>> >>>>> Given that ATA devices will be woken up by libata activity on resume, >>>>> sd_resume() has no need to issue a START STOP UNIT command, which solves >>>>> the above mentioned problems. Do not issue this command by introducing >>>>> the new scsi_device flag no_start_on_resume and setting this flag to 1 >>>>> in ata_scsi_dev_config(). sd_resume() is modified to issue a START STOP >>>>> UNIT command only if this flag is not set. >>>>> >>>>> Reported-by: Paul Ausbeck <paula@xxxxxxxxxxxx> >>>>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=215880 >>>>> Fixes: a19a93e4c6a9 ("scsi: core: pm: Rely on the device driver core for async power management") >>>>> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx> >>>> >>>> Thanks for your patch, which is now commit 0a8589055936d8fe >>>> ("ata,scsi: do not issue START STOP UNIT on resume") in v6.5-rc5. >>>> Sorry for being late to the party, but this commit landed upstream >>>> during my summer holidays, and apparently I wasn't that focussed on >>>> noticing small behavioral changes after getting back to work... >>>> >>>> I noticed an oddity after s2idle or s2ram on Renesas Salvator-XS (R-Car >>>> H3 ES2.0) with an old (spinning rust) SATA drive, and bisected it to >>>> this commit: when accessing the drive after system resume, there is now >>>> a delay of ca. 5s before data is returned, presumably due to starting >>>> the drive, and having to wait for it to spin up to be able to read data. >>>> But the good news is that the actual system resume takes less time than >>>> before (reduced by even more than ca. 5s!), so this looks like a net >>>> win... >>> >>> Thanks for the report. The delay for the first data access from user space right >>> after resume is 100% expected, with or without this patch. The reason is that >>> waking up the drive (spinning it up) is done asynchronously from the PM resume >>> context, so when you get "PM suspend exit" message signaling that the system is >>> resumed, the drive may not yet be spinning. Any access will wait for that to >>> happen before proceeding. Depending on the drive that can take up to 10s or so. >> >> That does not match with what I am seeing: before this patch, there >> was no delay on first data access from user space, as the drive is fully >> spun up when system resume returns. >> With this patch, system resume returns earlier, and the drive is only >> spun up when user space starts accessing data. >> >> Note that I do not have any file system mounted, and use >> "hd /dev/sda | head -70" to access the disk. >> >>> I am not entirely sure where the net win you see come from. But the patch you >>> mention is in fact completely wrong and does not fix the underlying issues with >>> ata suspend/resume and potential deadlocks in PM due to ata ports relationship >>> with scsi devices. So I have been working on fixing this for the last 2 weeks, >>> after another user also reported issues with the patch you mention [1]. >>> >>> Could you try libata for-next branch on your system ? There are 7 fix patches in >>> there that I plan to send out for 6.6-rc2 to fix the patch in question and other >>> issues potentially causing deadlocks on resume. The patches were posted also [2]. >>> >>> https://lore.kernel.org/linux-ide/20230912005655.368075-1-dlemoal@xxxxxxxxxx/T/#t >> >> Unfortunately that didn't work, as /dev/sda no longer exists. >> Will reply to the patch I bisected the issue to... > > With libata/for-next (fa2259a59966c005 ("ata: libata: Cleanup inline > DMA helper functions")) and commit 99626085d036ec32 ("ata: libata-scsi: > link ata port and scsi device") reverted, it behaves as before (disk > is spun up when system resume completes, no delay when accessing the > disk from userspace). I will check the ata platform driver for R-CAR. I may have overlooked something in that area. I tested with AHCI and libsas adapters only as I do not have ATA on the few ARM SBC boards I have. And I do not have an R-CAR board. What surprises me is that you need to revert ata: libata: Cleanup inline DMA helper functions". This patch has 0 functional changes and really is only a code cleanup... Nothing should change with it. Can you confirm that you really need to revert that patch to get things working again ? -- Damien Le Moal Western Digital Research
