On Wed, Oct 09, 2024 at 05:24:03PM -0500, Bjorn Helgaas wrote: > On Fri, Sep 13, 2024 at 11:01:23AM +0300, Mika Westerberg wrote: > > On Fri, Sep 13, 2024 at 02:00:58PM +0800, Kai-Heng Feng wrote: > > > On Fri, Sep 13, 2024 at 12:57 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > On Thu, Sep 12, 2024 at 11:00:43AM +0800, Kai-Heng Feng wrote: > > > > > On Thu, Sep 12, 2024 at 3:05 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > > > On Fri, Jul 12, 2024 at 02:24:11PM +0800, Kai-Heng Feng wrote: > > > > > > > Some laptops wake up after poweroff when HP Thunderbolt > > > > > > > Dock G4 is connected. > > > > > > > > > > > > > > The following error message can be found during shutdown: > > > > > > > pcieport 0000:00:1d.0: AER: Correctable error message received from 0000:09:04.0 > > > > > > > pcieport 0000:09:04.0: PCIe Bus Error: severity=Correctable, type=Data Link Layer, (Receiver ID) > > > > > > > pcieport 0000:09:04.0: device [8086:0b26] error status/mask=00000080/00002000 > > > > > > > pcieport 0000:09:04.0: [ 7] BadDLLP > > > > > > > > > > > > > > Calling aer_remove() during shutdown can quiesce the error > > > > > > > message, however the spurious wakeup still happens. > > > > > > > > > > > > > > The issue won't happen if the device is in D3 before > > > > > > > system shutdown, so putting device to low power state > > > > > > > before shutdown to solve the issue. > > > > > > > > > > > > > > I don't have a sniffer so this is purely guesswork, > > > > > > > however I believe putting device to low power state it's > > > > > > > the right thing to do. > > > > > > > > > > > > My objection here is that we don't have an explanation of > > > > > > why this should matter or a pointer to any spec language > > > > > > about this situation, so it feels a little bit random. > > ... > > > I don't mean to confuse you guys but with this one too, I wonder if you > > tried to "disable" the device instead of putting it into D3? On another > > thread (Mario at least is aware of this) I mentioned that our PCIe SV > > folks identified a couple issues in Linux implementation around power > > management and one thing that we are missing is to disable I/O and MMIO > > upon entering D3. > > ... > > This is really interesting -- did they discover a functional problem, > or did they just notice that we don't follow the PCI PM spec? The latter. > > +++ b/drivers/pci/pci.c > > @@ -2218,6 +2218,13 @@ static void do_pci_disable_device(struct pci_dev *dev) > > pci_command &= ~PCI_COMMAND_MASTER; > > pci_write_config_word(dev, PCI_COMMAND, pci_command); > > } > > + /* > > + * PCI PM 1.2 sec 8.2.2 says that when a function is put into D3 > > + * the OS needs to disable I/O and MMIO space in addition to bus > > + * mastering so do that here. > > + */ > > + pci_command &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY); > > + pci_write_config_word(dev, PCI_COMMAND, pci_command); > > > > pcibios_disable_device(dev); > > } > > This do_pci_disable_device() proposal is interesting. > > pci_enable_device() turns on PCI_COMMAND_MEMORY and PCI_COMMAND_IO, > which enables the device to respond to MMIO and I/O port accesses to > its BARs from the driver. It also makes sure the device is in D0, > because BAR access only works in D0. > > pci_set_master() turns on PCI_COMMAND_MASTER, which enables the device > to perform DMA (including generating MSIs). > > pci_disable_device() *sounds* like it should be the opposite of > pci_enable_device(), but it's currently basically the same as > pci_clear_master(), which clears PCI_COMMAND_MASTER to prevent DMA. > I didn't know about this text in 8.2.2, and I wish I knew why we > don't currently clear PCI_COMMAND_MEMORY and PCI_COMMAND_IO. > > If we want to pursue this, I think it should be split to its own patch > and moved out of pci_disable_device() because I don't think this path > necessary implies putting the device in D3, so I think it would fit > better with the spec if we cleared PCI_COMMAND_MEMORY and > PCI_COMMAND_IO in a path that explicitly does put it in D3. > > I think there's a significant chance of breaking something because > drivers are currently able to access BARs after pci_disable_device(), > and there are a LOT of callers. But if there's a problem it would > fix, we should definitely explore it. At the moment it does not seem to fix anything as far as I can tell so not sure how important it is. Of course from spec perspective we should probably deal with it.
