Hi Damien, On Thu, Sep 14, 2023 at 12:08 AM Damien Le Moal <dlemoal@xxxxxxxxxx> wrote: > On 9/13/23 19:34, Geert Uytterhoeven wrote: > > 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 ? My apologies, I should have written: With libata/for-next (which is currently at fa2259a59966c005 ("ata: libata: Cleanup inline DMA helper functions")), and commit 99626085d036ec32 ("ata: libata-scsi: link ata port and scsi device") reverted, ... So 99626085d036ec32 was the only commit I had to revert. Sorry for the confusion. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
