powerpc/powernv: Fix update of NVLink DMA mask

The emulated NVLink PCI devices share the same IODA2 TCE tables but only
support a single TVT (instead of the normal two for PCI devices). This
requires the kernel to manually replace windows with either the bypass
or non-bypass window depending on what the driver has requested.

Unfortunately an incorrect optimisation was made in
pnv_pci_ioda_dma_set_mask() which caused updating of some NPU device PEs
to be skipped in certain configurations due to an incorrect assumption
that a NULL peer PE in the array indicated there were no more peers
present. This patch fixes the problem by ensuring all peer PEs are
updated.

Fixes: 5d2aa71 ("powerpc/powernv: Add support for Nvlink NPUs")
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/pci-ioda.c

@@ -1612,7 +1612,10 @@ static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
 
 	/* Update peer npu devices */
 	if (pe->flags & PNV_IODA_PE_PEER)
-		for (i = 0; pe->peers[i]; i++) {
+		for (i = 0; i < PNV_IODA_MAX_PEER_PES; i++) {
+			if (!pe->peers[i])
+				continue;
+
 			linked_npu_dev = pe->peers[i]->pdev;
 			if (dma_get_mask(&linked_npu_dev->dev) != dma_mask)
 				dma_set_mask(&linked_npu_dev->dev, dma_mask);