linux-kernel - [PATCH v3 6/7] PCI: dwc: Introduce Configurable DMA mask

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Date:   Thu, 23 Feb 2023 20:05:30 +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 v3 6/7] 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.
If not defined, fallback to 32-bit as previously done in the code.
DT property is called num-dmamask , and can range between 33 and 64.

Signed-off-by: Elad Nachman <enachman@...vell.com>
---
 .../pci/controller/dwc/pcie-designware-host.c | 23 ++++++++++++++-----
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819..ac851b065325 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -204,7 +204,6 @@ static int dw_pcie_irq_domain_alloc(struct irq_domain *domain,
 				    pp->msi_irq_chip,
 				    pp, handle_edge_irq,
 				    NULL, NULL);
-
 	return 0;
 }
 
@@ -250,7 +249,6 @@ int dw_pcie_allocate_domains(struct dw_pcie_rp *pp)
 		irq_domain_remove(pp->irq_domain);
 		return -ENOMEM;
 	}
-
 	return 0;
 }
 
@@ -325,10 +323,12 @@ 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;
 
 	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
 		pp->irq_mask[ctrl] = ~0;
@@ -367,18 +367,30 @@ 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.
+	 * 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_property_read_u32(np, "num-dmamask", &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");
+		num_dma_maskbits = 32;
+
+	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(num_dma_maskbits));
+	if (ret)
+		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);
@@ -420,7 +432,6 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
 		dev_err(dev, "Missing *config* reg space\n");
 		return -ENODEV;
 	}
-
 	bridge = devm_pci_alloc_host_bridge(dev, 0);
 	if (!bridge)
 		return -ENOMEM;
-- 
2.17.1