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    Subject[PATCH v3 04/25] PCI: Remove redundant error fabrication when device read fails
    Date
    An MMIO read from a PCI device that doesn't exist or doesn't respond
    causes a PCI error. There's no real data to return to satisfy the
    CPU read, so most hardware fabricates ~0 data.

    The host controller drivers sets the error response values (~0) and
    returns an error when faulty hardware read occurs. But the error
    response value (~0) is already being set in PCI_OP_READ and
    PCI_USER_READ_CONFIG whenever a read by host controller driver fails.

    Thus, it's no longer necessary for the host controller drivers to
    fabricate any error response.

    This helps unify PCI error response checking and make error check
    consistent and easier to find.

    Reviewed-by: Rob Herring <robh@kernel.org>
    Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com>
    ---
    drivers/pci/access.c | 8 ++------
    1 file changed, 2 insertions(+), 6 deletions(-)

    diff --git a/drivers/pci/access.c b/drivers/pci/access.c
    index a6bcbad04d89..2705a4412e69 100644
    --- a/drivers/pci/access.c
    +++ b/drivers/pci/access.c
    @@ -83,10 +83,8 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
    void __iomem *addr;

    addr = bus->ops->map_bus(bus, devfn, where);
    - if (!addr) {
    - *val = ~0;
    + if (!addr)
    return PCIBIOS_DEVICE_NOT_FOUND;
    - }

    if (size == 1)
    *val = readb(addr);
    @@ -125,10 +123,8 @@ int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn,
    void __iomem *addr;

    addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
    - if (!addr) {
    - *val = ~0;
    + if (!addr)
    return PCIBIOS_DEVICE_NOT_FOUND;
    - }

    *val = readl(addr);

    --
    2.25.1
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