On Thu, Jul 02, 2020 at 10:30:36AM +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. > > This is just an optimization to prevent accessing PCIe registers when card > is disconnected. Trying to access PCIe registers of disconnected card does > not cause any crash, kernel just needs to wait for a timeout. So if card > disappear immediately after checking for PCIe link (before accessing PCIe > registers), it does not cause any problems. > > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > > --- > Changes in V3: > * Add comment to the code > Changes in V2: > * Update commit message, mention that this is optimization > --- > drivers/pci/controller/pci-aardvark.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c > index 90ff291c24f0..d18f389b36a1 100644 > --- a/drivers/pci/controller/pci-aardvark.c > +++ b/drivers/pci/controller/pci-aardvark.c > @@ -644,6 +644,13 @@ 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 the link goes down after we check for link-up, nothing bad > + * happens but the config access times out. > + */ > + if (bus->number != pcie->root_bus_nr && !advk_pcie_link_up(pcie)) > + return false; > + > return true; > } Question: this basically means that you can only effectively enumerate bus number == root_bus_nr and AFAICS if at probe the link did not come up it will never do, will it ? Isn't this equivalent to limiting the bus numbers the bridge is capable of handling ? Reworded: if in advk_pcie_setup_hw() the link does not come up, what's the point of trying to enumerate the bus hierarchy below the root bus ? Thanks, Lorenzo
