PCI: Restore resized BAR state on resume

Resize BARs after resume to the expected size again.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199959
Fixes: d6895ad39f3b ("drm/amdgpu: resize VRAM BAR for CPU access v6")
Fixes: 276b738deb5b ("PCI: Add resizable BAR infrastructure")
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org      # v4.15+

drivers/pci/pci.c

@@ -1171,6 +1171,33 @@ static void pci_restore_config_space(struct pci_dev *pdev)
 	}
 }
 
+static void pci_restore_rebar_state(struct pci_dev *pdev)
+{
+	unsigned int pos, nbars, i;
+	u32 ctrl;
+
+	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
+	if (!pos)
+		return;
+
+	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+	nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >>
+		    PCI_REBAR_CTRL_NBAR_SHIFT;
+
+	for (i = 0; i < nbars; i++, pos += 8) {
+		struct resource *res;
+		int bar_idx, size;
+
+		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
+		res = pdev->resource + bar_idx;
+		size = order_base_2((resource_size(res) >> 20) | 1) - 1;
+		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
+		ctrl |= size << 8;
+		pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
+	}
+}
+
 /**
  * pci_restore_state - Restore the saved state of a PCI device
  * @dev: - PCI device that we're dealing with
@@ -1186,6 +1213,7 @@ void pci_restore_state(struct pci_dev *dev)
 	pci_restore_pri_state(dev);
 	pci_restore_ats_state(dev);
 	pci_restore_vc_state(dev);
+	pci_restore_rebar_state(dev);
 
 	pci_cleanup_aer_error_status_regs(dev);