[PATCH 4/4] cxl/pci: Guard decoder accesses after reset

[Richard Cheng <icheng@nvidia.com>]

cxl_reset_done() runs even when PCI state restoration is skipped.
Reading HDM decoder registers while the device is inaccessible can
trigger another error.

Skip decoder checks if the PCI Command read fails, returns all ones, or
Memory Space Enable is clear.

Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 drivers/cxl/pci.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index c7c91e8dc51d..2294f7761e50 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -976,6 +976,12 @@ static void cxl_reset_done(struct pci_dev *pdev)
 	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
 	struct cxl_memdev *cxlmd = cxlds->cxlmd;
 	struct device *dev = &pdev->dev;
+	u32 command;
+
+	/* PCI state restoration may have been skipped after a failed reset. */
+	if (pci_read_config_dword(pdev, PCI_COMMAND, &command) ||
+	    PCI_POSSIBLE_ERROR(command) || !(command & PCI_COMMAND_MEMORY))
+		return;
 
 	/*
 	 * FLR does not expect to touch the HDM decoders and related
-- 
2.43.0