On Thursday 28 May 2020 11:26:04 Bjorn Helgaas wrote: > On Thu, May 28, 2020 at 04:31:41PM +0200, Pali Rohár wrote: > > When there is no PCIe card connected and advk_pcie_rd_conf() or > > advk_pcie_wr_conf() is called for PCI bus which doesn't belong to emulated > > root bridge, the aardvark driver throws the following error message: > > > > advk-pcie d0070000.pcie: config read/write timed out > > > > Obviously accessing PCIe registers of disconnected card is not possible. > > > > Extend check in advk_pcie_valid_device() function for validating > > availability of PCIe bus. If PCIe link is down, then the device is marked > > as Not Found and the driver does not try to access these registers. > > > > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > > --- > > drivers/pci/controller/pci-aardvark.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c > > index 90ff291c24f0..53a4cfd7d377 100644 > > --- a/drivers/pci/controller/pci-aardvark.c > > +++ b/drivers/pci/controller/pci-aardvark.c > > @@ -644,6 +644,9 @@ static bool advk_pcie_valid_device(struct advk_pcie *pcie, struct pci_bus *bus, > > if ((bus->number == pcie->root_bus_nr) && PCI_SLOT(devfn) != 0) > > return false; > > > > + if (bus->number != pcie->root_bus_nr && !advk_pcie_link_up(pcie)) > > + return false; > > I don't think this is the right fix. This makes it racy because the > link may go down after we call advk_pcie_valid_device() but before we > perform the config read. Yes, it is racy, but I do not think it cause problems. Trying to read PCIe registers when device is not connected cause just those timeouts, printing error message and increased delay in advk_pcie_wait_pio() due to polling loop. This patch reduce unnecessary access to PCIe registers when advk_pcie_wait_pio() polling just fail. I think it is a good idea to not call blocking advk_pcie_wait_pio() when it is not needed. We could have faster enumeration of PCIe buses when card is not connected. > I have no objection to removing the "config read/write timed out" > message. The "return PCIBIOS_SET_FAILED" in the read case probably > should be augmented by setting "*val = 0xffffffff". > > > return true; > > } > > > > -- > > 2.20.1 > >
