On Mon, Jan 29, 2024 at 01:27:10PM +0200, Ilpo Järvinen wrote: > On runtime resume, pci_dev_wait() is called: > pci_pm_runtime_resume() > pci_pm_bridge_power_up_actions() > pci_bridge_wait_for_secondary_bus() > pci_dev_wait() > > While a device is runtime suspended along with its PCIe hierarchy, the > device could get disconnected. In such case, the link will not come up > no matter how log pci_dev_wait() waits for it. s/PCIe/PCI/ (unless this is a PCIe-specific thing) s/log/long/ > Besides the above mentioned case, there could be other ways to get the > device disconnected while pci_dev_wait() is waiting for the link to > come up. > > Make pci_dev_wait() to exit if the device is already disconnected to > avoid unnecessary delay. As disconnected device is not really even a > failure in the same sense as link failing to come up for whatever > reason, return 0 instead of errno. The device being disconnected is not the same as a link failure. Do all the callers do the right thing if pci_dev_wait() returns success when there's no device there? > Also make sure compiler does not become too clever with > dev->error_state and use READ_ONCE() to force a fetch for the > up-to-date value. I think we should have a comment there to say why READ_ONCE() is needed. Otherwise it's hard to know whether a future change might make it unnecessary. > Reported-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Tested-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> > --- > drivers/pci/pci.c | 5 +++++ > drivers/pci/pci.h | 4 +++- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index d8f11a078924..ec9bf6c90312 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -1250,6 +1250,11 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout) > for (;;) { > u32 id; > > + if (pci_dev_is_disconnected(dev)) { > + pci_dbg(dev, "disconnected; not waiting\n"); > + return 0; > + } > + > pci_read_config_dword(dev, PCI_COMMAND, &id); > if (!PCI_POSSIBLE_ERROR(id)) > break; > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 2336a8d1edab..563a275dff67 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -4,6 +4,8 @@ > > #include <linux/pci.h> > > +#include <asm/rwonce.h> > + > /* Number of possible devfns: 0.0 to 1f.7 inclusive */ > #define MAX_NR_DEVFNS 256 > > @@ -370,7 +372,7 @@ static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused) > > static inline bool pci_dev_is_disconnected(const struct pci_dev *dev) > { > - return dev->error_state == pci_channel_io_perm_failure; > + return READ_ONCE(dev->error_state) == pci_channel_io_perm_failure; > } > > /* pci_dev priv_flags */ > -- > 2.39.2 >