linux-kernel - [PATCH v4 01/17] PCI: dwc: Use the DMA-API to get the MSI address

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Date:   Fri,  3 Nov 2017 14:47:05 +0100
From:   Niklas Cassel <niklas.cassel@...s.com>
To:     Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Niklas Cassel <niklass@...s.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 01/17] PCI: dwc: Use the DMA-API to get the MSI address

Use the DMA-API to get the MSI address. This address will be written to
our PCI config space and to the register which determines which AXI
address the DWC IP will spoof for incoming MSI irqs.

Since it is a PCIe endpoint device, rather than the CPU, that is supposed
to write to the MSI address, the proper way to get the MSI address is by
using the DMA API, not by using virt_to_phys().

Using virt_to_phys() might work on some systems, but using the DMA API
should work on all systems.

This is essentially the same thing as allocating a buffer in a driver
to which the endpoint will write to. To do this, we use the DMA API.

Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>
---
 drivers/pci/dwc/pcie-designware-host.c | 15 ++++++++++++---
 drivers/pci/dwc/pcie-designware.h      |  3 ++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
index 81e2157a7cfb..33b52fe98a01 100644
--- a/drivers/pci/dwc/pcie-designware-host.c
+++ b/drivers/pci/dwc/pcie-designware-host.c
@@ -83,10 +83,19 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
 
 void dw_pcie_msi_init(struct pcie_port *pp)
 {
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct device *dev = pci->dev;
+	struct page *page;
 	u64 msi_target;
 
-	pp->msi_data = __get_free_pages(GFP_KERNEL, 0);
-	msi_target = virt_to_phys((void *)pp->msi_data);
+	page = alloc_page(GFP_KERNEL | GFP_DMA32);
+	pp->msi_data = dma_map_page(dev, page, 0, PAGE_SIZE, DMA_FROM_DEVICE);
+	if (dma_mapping_error(dev, pp->msi_data)) {
+		dev_err(dev, "failed to map MSI data\n");
+		__free_page(page);
+		return;
+	}
+	msi_target = (u64)pp->msi_data;
 
 	/* program the msi_data */
 	dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_LO, 4,
@@ -187,7 +196,7 @@ static void dw_msi_setup_msg(struct pcie_port *pp, unsigned int irq, u32 pos)
 	if (pp->ops->get_msi_addr)
 		msi_target = pp->ops->get_msi_addr(pp);
 	else
-		msi_target = virt_to_phys((void *)pp->msi_data);
+		msi_target = (u64)pp->msi_data;
 
 	msg.address_lo = (u32)(msi_target & 0xffffffff);
 	msg.address_hi = (u32)(msi_target >> 32 & 0xffffffff);
diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
index e5d9d77b778e..ecdede68522a 100644
--- a/drivers/pci/dwc/pcie-designware.h
+++ b/drivers/pci/dwc/pcie-designware.h
@@ -14,6 +14,7 @@
 #ifndef _PCIE_DESIGNWARE_H
 #define _PCIE_DESIGNWARE_H
 
+#include <linux/dma-mapping.h>
 #include <linux/irq.h>
 #include <linux/msi.h>
 #include <linux/pci.h>
@@ -168,7 +169,7 @@ struct pcie_port {
 	const struct dw_pcie_host_ops *ops;
 	int			msi_irq;
 	struct irq_domain	*irq_domain;
-	unsigned long		msi_data;
+	dma_addr_t		msi_data;
 	DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
 };
 
-- 
2.14.2