On Sat, Mar 8, 2014 at 2:04 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > [+cc Rafael] > > On Fri, Mar 07, 2014 at 11:39:48AM -0800, Yinghai Lu wrote: >> On Fri, Mar 7, 2014 at 8:45 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: >> > >> > I opened a bugzilla report at https://bugzilla.kernel.org/show_bug.cgi?id=71691 >> > >> > It seems like clearing DisINTx has some effect on MSI. I don't see >> > anything in the spec that would suggest this (I'm looking at the PCIe >> > r3.0 spec, sec 7.5.1.1). >> > >> > Can somebody point out a connection between DisINTx and MSI? If not, >> > maybe we'll need some sort of quirk to deal with this. >> >> I had different impression: if you disable INTx in some chipset, MSI will not >> work anymore. >> >> so we have >> >> static void pci_intx_for_msi(struct pci_dev *dev, int enable) >> { >> if (!(dev->dev_flags & PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG)) >> pci_intx(dev, enable); >> } >> >> and have quirks for ati and broadcom chip to set that FLAG. > > Setting INTX_DISABLE on some chipsets seems to disable MSI, and that > behavior seems to be a hardware defect (see ba698ad4b7e4 "PCI: Add > quirk for devices which disable MSI when INTX_DISABLE is set.") > > Andreas has a device where *clearing* INTX_DISABLE seems to disable > MSI. Do you think that's also a hardware defect? If it's not a > defect, is there something in the spec that explains why that happens? > >> regarding the regression: i would suggest move out >> do_pci_enable_intx() from re-enable path. > > Today we have this: > > pcie_portdrv_probe > pci_enable_device # clears INTX_DISABLE > pci_enable_msi # sets INTX_DISABLE > > pciehp_configure_device > pci_reenable_device # clears INTX_DISABLE again > > This is clearly not the intent; we set INTX_DISABLE when MSI was > enabled, then we clear it again later even though MSI is still > enabled. Maybe we should just leave INTX_DISABLE alone if > (dev->msi_enabled || dev->msix_enabled). > > pci_reenable_device() is also used in the device resume path. I don't > know what should happen there. > > But I'm curious about why we set INTX_DISABLE when enabling MSI/MSI-X > in the first place. Per the PCI 3.0 spec, sec 6.8.3.3: > > While enabled for MSI or MSI-X operation, a function is prohibited > from using its INTx# pin (if implemented) to request service (MSI, > MSI-X, and INTx# are mutually exclusive). > > This suggests that we might not need to touch INTX_DISABLE when we're > enabling MSI/MSI-X. I looked at these commits related to it: > > ba698ad4b7e4 PCI: Add quirk for devices which disable MSI when INTX_DISABLE is set. > b1cbf4e4dddd msi: fix up the msi enable/disable logic > 1769b46a3ed9 PCI MSI: always toggle legacy-INTx-enable bit upon MSI entry/exit > 986162d3239a ia32 Message Signalled Interrupt support > > and none of them mentions a problem that requires us to set > INTX_DISABLE. It's possible that we're causing ourselves trouble by > being overly defensive. I wonder what would happen if we stopped > fiddling with it in the MSI/MSI-X paths, e.g., something like this > (just as an experiment, of course): > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c > index 7a0fec6ce571..9ef7bd608add 100644 > --- a/drivers/pci/msi.c > +++ b/drivers/pci/msi.c > @@ -442,8 +442,6 @@ static struct msi_desc *alloc_msi_entry(struct pci_dev *dev) > > static void pci_intx_for_msi(struct pci_dev *dev, int enable) > { > - if (!(dev->dev_flags & PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG)) > - pci_intx(dev, enable); > } > > static void __pci_restore_msi_state(struct pci_dev *dev) > > If we did that, INTX_DISABLE would be cleared by the first > pci_enable_device() and pci_reenable_device() wouldn't do anything, > leaving it cleared. The resulting state (cleared) would be the same, > but the transitions would be gone, and maybe those are important. Just a quick note: With pci_intx_for_msi removed no hotplug events are ever delivered. Everything else still works though. So it is either a problem specific to Thunderbolt bridges or maybe it just affects hotplug (and PME?) interrupts. I also attempted booting with pcie_hp=nomsi and now everything works. Interestingly pciehp now also gets an interrupt from 09 (event though that card has just been removed). I suspect this is just pciehp not noticing that it itself is gone. pciehp 0000:06:03.0:pcie24: Card not present on Slot(3-1) pciehp 0000:09:00.0:pcie24: Latch open on Slot(9) pciehp 0000:09:00.0:pcie24: Button pressed on Slot(9) pciehp 0000:09:00.0:pcie24: Card present on Slot(9) pciehp 0000:09:00.0:pcie24: Power fault on slot 9 pciehp 0000:09:00.0:pcie24: Power fault bit 0 set pciehp 0000:09:00.0:pcie24: PCI slot #9 - powering on due to button press. pciehp 0000:09:00.0:pcie24: unloading service driver pciehp pciehp 0000:09:00.0:pcie24: Link Training Error occurs pciehp 0000:09:00.0:pcie24: Failed to check link status > The thing I don't like about the patch below is that it's magical: the > code doesn't have any obvious connection with the problem. How would > one deduce that this is necessary, or explain why it's necessary? A > changelog like "this makes things work" is not really very useful. If > we make a change like this, it needs to be connected with MSI/MSI-X > somehow so a reader can figure out why we twiddle INTX_DISABLE in the > enable path but not the reenable path. > > Bjorn > >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index 5a24cb3..92718c9 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -1190,11 +1190,22 @@ int __weak pcibios_enable_device(struct >> pci_dev *dev, int bars) >> return pci_enable_resources(dev, bars); >> } >> >> +static void do_pci_enable_intx(struct pci_dev *dev) >> +{ >> + u8 pin; >> + pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin); >> + if (pin) { >> + pci_read_config_word(dev, PCI_COMMAND, &cmd); >> + if (cmd & PCI_COMMAND_INTX_DISABLE) >> + pci_write_config_word(dev, PCI_COMMAND, >> + cmd & ~PCI_COMMAND_INTX_DISABLE); >> + } >> +} >> + >> static int do_pci_enable_device(struct pci_dev *dev, int bars) >> { >> int err; >> u16 cmd; >> - u8 pin; >> >> err = pci_set_power_state(dev, PCI_D0); >> if (err < 0 && err != -EIO) >> @@ -1204,14 +1215,6 @@ static int do_pci_enable_device(struct pci_dev >> *dev, int bars) >> return err; >> pci_fixup_device(pci_fixup_enable, dev); >> >> - pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin); >> - if (pin) { >> - pci_read_config_word(dev, PCI_COMMAND, &cmd); >> - if (cmd & PCI_COMMAND_INTX_DISABLE) >> - pci_write_config_word(dev, PCI_COMMAND, >> - cmd & ~PCI_COMMAND_INTX_DISABLE); >> - } >> - >> return 0; >> } >> >> @@ -1287,6 +1290,8 @@ static int pci_enable_device_flags(struct >> pci_dev *dev, unsigned long flags) >> err = do_pci_enable_device(dev, bars); >> if (err < 0) >> atomic_dec(&dev->enable_cnt); >> + else >> + do_pci_enable_intx(dev); >> return err; >> } > >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index 5a24cb3..92718c9 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -1190,11 +1190,22 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars) >> return pci_enable_resources(dev, bars); >> } >> >> +static void do_pci_enable_intx(struct pci_dev *dev) >> +{ >> + u8 pin; >> + pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin); >> + if (pin) { >> + pci_read_config_word(dev, PCI_COMMAND, &cmd); >> + if (cmd & PCI_COMMAND_INTX_DISABLE) >> + pci_write_config_word(dev, PCI_COMMAND, >> + cmd & ~PCI_COMMAND_INTX_DISABLE); >> + } >> +} >> + >> static int do_pci_enable_device(struct pci_dev *dev, int bars) >> { >> int err; >> u16 cmd; >> - u8 pin; >> >> err = pci_set_power_state(dev, PCI_D0); >> if (err < 0 && err != -EIO) >> @@ -1204,14 +1215,6 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars) >> return err; >> pci_fixup_device(pci_fixup_enable, dev); >> >> - pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin); >> - if (pin) { >> - pci_read_config_word(dev, PCI_COMMAND, &cmd); >> - if (cmd & PCI_COMMAND_INTX_DISABLE) >> - pci_write_config_word(dev, PCI_COMMAND, >> - cmd & ~PCI_COMMAND_INTX_DISABLE); >> - } >> - >> return 0; >> } >> >> @@ -1287,6 +1290,8 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) >> err = do_pci_enable_device(dev, bars); >> if (err < 0) >> atomic_dec(&dev->enable_cnt); >> + else >> + do_pci_enable_intx(dev); >> return err; >> } >> > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
