[PATCH 01/11] Revert "powerpc/powernv: Remove unused pnv_npu_try_dma_set_bypass() function"

[Reza Arbab <arbab@linux.ibm.com>]

Revert commit b4d37a7b6934 ("powerpc/powernv: Remove unused
pnv_npu_try_dma_set_bypass() function") so that this function can be
reintegrated.

Fixes: 2d6ad41b2c21 ("powerpc/powernv: use the generic iommu bypass code")
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
---
 arch/powerpc/platforms/powernv/npu-dma.c | 99 ++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index b95b9e3c4c98..5a8313654033 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -193,6 +193,105 @@ static long pnv_npu_unset_window(struct iommu_table_group *table_group, int num)
 	return 0;
 }
 
+/*
+ * Enables 32 bit DMA on NPU.
+ */
+static void pnv_npu_dma_set_32(struct pnv_ioda_pe *npe)
+{
+	struct pci_dev *gpdev;
+	struct pnv_ioda_pe *gpe;
+	int64_t rc;
+
+	/*
+	 * Find the assoicated PCI devices and get the dma window
+	 * information from there.
+	 */
+	if (!npe->pdev || !(npe->flags & PNV_IODA_PE_DEV))
+		return;
+
+	gpe = get_gpu_pci_dev_and_pe(npe, &gpdev);
+	if (!gpe)
+		return;
+
+	rc = pnv_npu_set_window(&npe->table_group, 0,
+			gpe->table_group.tables[0]);
+
+	/*
+	 * NVLink devices use the same TCE table configuration as
+	 * their parent device so drivers shouldn't be doing DMA
+	 * operations directly on these devices.
+	 */
+	set_dma_ops(&npe->pdev->dev, &dma_dummy_ops);
+}
+
+/*
+ * Enables bypass mode on the NPU. The NPU only supports one
+ * window per link, so bypass needs to be explicitly enabled or
+ * disabled. Unlike for a PHB3 bypass and non-bypass modes can't be
+ * active at the same time.
+ */
+static int pnv_npu_dma_set_bypass(struct pnv_ioda_pe *npe)
+{
+	struct pnv_phb *phb = npe->phb;
+	int64_t rc = 0;
+	phys_addr_t top = memblock_end_of_DRAM();
+
+	if (phb->type != PNV_PHB_NPU_NVLINK || !npe->pdev)
+		return -EINVAL;
+
+	rc = pnv_npu_unset_window(&npe->table_group, 0);
+	if (rc != OPAL_SUCCESS)
+		return rc;
+
+	/* Enable the bypass window */
+
+	top = roundup_pow_of_two(top);
+	dev_info(&npe->pdev->dev, "Enabling bypass for PE %x\n",
+			npe->pe_number);
+	rc = opal_pci_map_pe_dma_window_real(phb->opal_id,
+			npe->pe_number, npe->pe_number,
+			0 /* bypass base */, top);
+
+	if (rc == OPAL_SUCCESS)
+		pnv_pci_ioda2_tce_invalidate_entire(phb, false);
+
+	return rc;
+}
+
+void pnv_npu_try_dma_set_bypass(struct pci_dev *gpdev, bool bypass)
+{
+	int i;
+	struct pnv_phb *phb;
+	struct pci_dn *pdn;
+	struct pnv_ioda_pe *npe;
+	struct pci_dev *npdev;
+
+	for (i = 0; ; ++i) {
+		npdev = pnv_pci_get_npu_dev(gpdev, i);
+
+		if (!npdev)
+			break;
+
+		pdn = pci_get_pdn(npdev);
+		if (WARN_ON(!pdn || pdn->pe_number == IODA_INVALID_PE))
+			return;
+
+		phb = pci_bus_to_host(npdev->bus)->private_data;
+
+		/* We only do bypass if it's enabled on the linked device */
+		npe = &phb->ioda.pe_array[pdn->pe_number];
+
+		if (bypass) {
+			dev_info(&npdev->dev,
+					"Using 64-bit DMA iommu bypass\n");
+			pnv_npu_dma_set_bypass(npe);
+		} else {
+			dev_info(&npdev->dev, "Using 32-bit DMA via iommu\n");
+			pnv_npu_dma_set_32(npe);
+		}
+	}
+}
+
 /* Switch ownership from platform code to external user (e.g. VFIO) */
 static void pnv_npu_take_ownership(struct iommu_table_group *table_group)
 {
-- 
1.8.3.1