linux-kernel - [PATCH v4 7/8] PCI: dwc: Introduce configurable DMA mask

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Date:   Mon, 13 Mar 2023 14:40:15 +0200
From:   Elad Nachman <enachman@...vell.com>
To:     <thomas.petazzoni@...tlin.com>, <bhelgaas@...gle.com>,
        <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <linux-pci@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Elad Nachman <enachman@...vell.com>
Subject: [PATCH v4 7/8] PCI: dwc: Introduce configurable DMA mask

From: Elad Nachman <enachman@...vell.com>

Some devices, such as AC5 and AC5X have their physical DDR memory
start at address 0x2_0000_0000. In order to have the DMA coherent
allocation succeed later, a different DMA mask is required, as
defined in the DT file for such SOCs, using dma-ranges.

If not defined, fallback to 32-bit as previously done in the code.

Signed-off-by: Elad Nachman <enachman@...vell.com>
---
v4:
   1) Fix commit message formatting.

   2) Fix removal / addition of blank lines.

 .../pci/controller/dwc/pcie-designware-host.c | 28 +++++++++++++++++--
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819..74393e59e7a7 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -325,10 +325,14 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct device *dev = pci->dev;
+	struct device_node *np = dev->of_node;
 	struct platform_device *pdev = to_platform_device(dev);
 	u64 *msi_vaddr;
 	int ret;
 	u32 ctrl, num_ctrls;
+	u32 num_dma_maskbits = 32;
+	struct of_pci_range range;
+	struct of_pci_range_parser parser;
 
 	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
 		pp->irq_mask[ctrl] = ~0;
@@ -367,18 +371,36 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 	}
 
 	/*
+	 * Some devices, such as AC5 and AC5X have their physical DDR memory
+	 * start at address 0x2_0000_0000 . In order to have the DMA
+	 * coherent allocation succeed later, a different DMA mask is
+	 * required, as defined in the DT file for such SOCs using dma-ranges.
+	 * If not defined, fallback to 32-bit as described below:
+	 *
 	 * Even though the iMSI-RX Module supports 64-bit addresses some
 	 * peripheral PCIe devices may lack 64-bit message support. In
 	 * order not to miss MSI TLPs from those devices the MSI target
 	 * address has to be within the lowest 4GB.
 	 *
-	 * Note until there is a better alternative found the reservation is
+	 * Note until there is a better alternative found, the reservation is
 	 * done by allocating from the artificially limited DMA-coherent
 	 * memory.
 	 */
-	ret = dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
+	ret = of_pci_dma_range_parser_init(&parser, np);
+	if (!ret) {
+		if (of_pci_range_parser_one(&parser, &range)) {
+			if (range.size > BIT_MASK(32) ) {
+				num_dma_maskbits = fls64(range.size);
+				dev_info(dev, "Overriding DMA mask to %u bits...\n", num_dma_maskbits);
+			}
+		}
+	}
+
+	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(num_dma_maskbits));
 	if (ret)
-		dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n");
+		dev_warn(dev,
+			 "Failed to set DMA mask to %u-bit. Devices with only 32-bit MSI support may not work properly\n",
+			 num_dma_maskbits);
 
 	msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data,
 					GFP_KERNEL);
-- 
2.17.1