PCI: endpoint: pci-epf-test: Roll back BAR mapping when subrange setup fails

When the BAR subrange mapping test on DWC-based platforms fails due to
insufficient free inbound iATU regions, pci_epf_test_bar_subrange_setup()
returns an error (-ENOSPC) but does not restore the original BAR mapping.
This causes subsequent test runs to become confusing, since the failure may
leave room for the next subrange mapping test to pass.

Fix this by restoring the original BAR mapping when preparation of the
subrange mapping fails, so that no side effect remains regardless of the
test success or failure.

Fixes: 6c5e610 ("PCI: endpoint: pci-epf-test: Add BAR subrange mapping test support")
Reported-by: Christian Bruel <[email protected]>
Closes: https://lore.kernel.org/linux-pci/[email protected]/
Signed-off-by: Koichiro Den <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Tested-by: Christian Bruel <[email protected]>
Reviewed-by: Niklas Cassel <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: Koichiro Den

drivers/pci/endpoint/functions/pci-epf-test.c

@@ -894,6 +894,11 @@ static void pci_epf_test_bar_subrange_setup(struct pci_epf_test *epf_test,
 		dev_err(&epf->dev, "pci_epc_set_bar() failed: %d\n", ret);
 		bar->submap = old_submap;
 		bar->num_submap = old_nsub;
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, bar);
+		if (ret)
+			dev_warn(&epf->dev, "Failed to restore the original BAR mapping: %d\n",
+				 ret);
+
 		kfree(submap);
 		goto err;
 	}