linux-kernel - [PATCH 01/10] PCI: dwc: use DMA-API for allocating MSI data

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Date:   Fri, 13 Oct 2017 18:09:04 +0200
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 01/10] PCI: dwc: use DMA-API for allocating MSI data

Since it is a PCIe endpoint device, rather than the CPU, that is supposed
to write to this location, the proper way to get the address to this this
location is really to use the DMA API, rather than virt_to_phys.

Using virt_to_phys might work on some systems, but by using the DMA API,
we know that it will 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 | 23 ++++++++++++++++-------
 drivers/pci/dwc/pcie-designware.h      |  3 ++-
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
index 81e2157a7cfb..f6d152ea2a03 100644
--- a/drivers/pci/dwc/pcie-designware-host.c
+++ b/drivers/pci/dwc/pcie-designware-host.c
@@ -83,16 +83,25 @@ 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,
-			    (u32)(msi_target & 0xffffffff));
+			    lower_32_bits(msi_target));
 	dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_HI, 4,
-			    (u32)(msi_target >> 32 & 0xffffffff));
+			    upper_32_bits(msi_target));
 }
 
 static void dw_pcie_msi_clear_irq(struct pcie_port *pp, int irq)
@@ -187,10 +196,10 @@ 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);
+	msg.address_lo = lower_32_bits(msi_target);
+	msg.address_hi = upper_32_bits(msi_target);
 
 	if (pp->ops->get_msi_data)
 		msg.data = pp->ops->get_msi_data(pp, pos);
diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
index e5d9d77b778e..547352a317f8 100644
--- a/drivers/pci/dwc/pcie-designware.h
+++ b/drivers/pci/dwc/pcie-designware.h
@@ -17,6 +17,7 @@
 #include <linux/irq.h>
 #include <linux/msi.h>
 #include <linux/pci.h>
+#include <linux/dma-mapping.h>
 
 #include <linux/pci-epc.h>
 #include <linux/pci-epf.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);
 };
 
-- 
2.11.0