PCI: Set error response data when config read fails

When a PCI config read fails, most PCI host bridges fabricate ~0 data to
complete the CPU read.  But some host bridges do not; their drivers may
only return an error from the pci_ops.read() method.

In PCI_OP_READ() and PCI_USER_READ_CONFIG(), use PCI_SET_ERROR_RESPONSE()
to set the data value to indicate an error when pci_ops.read() fails.

This means the host bridge driver no longer needs to fabricate error data
when they detect errors.

This makes error response fabrication consistent and helps in removal of a
lot of repeated code.

Suggested-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/4188fc5465631ce0d472d1423de3d9fb2f09b8ff.1637243717.git.naveennaidu479@gmail.com
Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Pali Rohár <pali@kernel.org>

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 4693569..eac0765 100644 (file)
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -42,7 +42,10 @@ int noinline pci_bus_read_config_##size \
        if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
        pci_lock_config(flags);                                         \
        res = bus->ops->read(bus, devfn, pos, len, &data);              \
-       *value = (type)data;                                            \
+       if (res)                                                        \
+               PCI_SET_ERROR_RESPONSE(value);                          \
+       else                                                            \
+               *value = (type)data;                                    \
        pci_unlock_config(flags);                                       \
        return res;                                                     \
 }
@@ -228,7 +231,10 @@ int pci_user_read_config_##size                                            \
        ret = dev->bus->ops->read(dev->bus, dev->devfn,                 \
                                        pos, sizeof(type), &data);      \
        raw_spin_unlock_irq(&pci_lock);                         \
-       *val = (type)data;                                              \
+       if (ret)                                                        \
+               PCI_SET_ERROR_RESPONSE(val);                            \
+       else                                                            \
+               *val = (type)data;                                      \
        return pcibios_err_to_errno(ret);                               \
 }                                                                      \
 EXPORT_SYMBOL_GPL(pci_user_read_config_##size);