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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, May 28, 2020 at 06:38:09PM +0200, Pali Roh=E1r wrote: > On Thursday 28 May 2020 11:26:04 Bjorn Helgaas wrote: > > On Thu, May 28, 2020 at 04:31:41PM +0200, Pali Roh=E1r 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 emu= lated > > > 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 possib= le. > > > = > > > Extend check in advk_pcie_valid_device() function for validating > > > availability of PCIe bus. If PCIe link is down, then the device is ma= rked > > > as Not Found and the driver does not try to access these registers. > > > = > > > Signed-off-by: Pali Roh=E1r > > > --- > > > drivers/pci/controller/pci-aardvark.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > = > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/cont= roller/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_pc= ie *pcie, struct pci_bus *bus, > > > if ((bus->number =3D=3D pcie->root_bus_nr) && PCI_SLOT(devfn) !=3D = 0) > > > return false; > > > = > > > + if (bus->number !=3D 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. Maybe advk_pcie_check_pio_status() and advk_pcie_wait_pio() could be combined so we could get the correct error status as soon as it's available, without waiting for a timeout? In any event, the "return PCIBIOS_SET_FAILED" needs to be fixed. Most callers of config read do not check for failure, but most of the ones that do, check for "val =3D=3D ~0". Only a few check for a status of other than PCIBIOS_SUCCESSFUL. > > 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 =3D 0xffffffff". > > = > > > return true; > > > } > > > = > > > -- = > > > 2.20.1 > > > = _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel