PCI: xilinx: Don't allocate extra memory for the MSI capture address

A long cargo-culted behaviour of PCI drivers is to allocate memory
to obtain an address that is fed to the controller as the MSI
capture address (i.e. the MSI doorbell).

But there is no actual requirement for this address to be RAM.
All it needs to be is a suitable aligned address that will
*not* be DMA'd to.

Use the physical address of the 'port' data structure as the MSI
capture address, aligned on a 4K boundary.

Link: https://lore.kernel.org/r/20210330151145.997953-5-maz@kernel.org
Tested-by: Bharat Kumar Gogada <bharatku@xilinx.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

diff --git a/drivers/pci/controller/pcie-xilinx.c b/drivers/pci/controller/pcie-xilinx.c
index fa5baeb8265349a80d98d728b4aae8ab17fa91a5..e127a7b6e5350a033d6ccf4000c4fc5a5ba79242 100644 (file)
--- a/drivers/pci/controller/pcie-xilinx.c
+++ b/drivers/pci/controller/pcie-xilinx.c
@@ -94,7 +94,6 @@
  * struct xilinx_pcie_port - PCIe port information
  * @reg_base: IO Mapped Register Base
  * @irq: Interrupt number
- * @msi_pages: MSI pages
  * @dev: Device pointer
  * @msi_domain: MSI IRQ domain pointer
  * @leg_domain: Legacy IRQ domain pointer
@@ -103,7 +102,6 @@
 struct xilinx_pcie_port {
        void __iomem *reg_base;
        u32 irq;
-       unsigned long msi_pages;
        struct device *dev;
        struct irq_domain *msi_domain;
        struct irq_domain *leg_domain;
@@ -274,10 +272,10 @@ static int xilinx_pcie_msi_setup_irq(struct msi_controller *chip,
 
        irq_set_msi_desc(irq, desc);
 
-       msg_addr = virt_to_phys((void *)port->msi_pages);
+       msg_addr = ALIGN_DOWN(virt_to_phys(port), SZ_4K);
 
-       msg.address_hi = 0;
-       msg.address_lo = msg_addr;
+       msg.address_hi = upper_32_bits(msg_addr);
+       msg.address_lo = lower_32_bits(msg_addr);
        msg.data = irq;
 
        pci_write_msi_msg(irq, &msg);
@@ -330,13 +328,9 @@ static int xilinx_pcie_enable_msi(struct xilinx_pcie_port *port)
 {
        phys_addr_t msg_addr;
 
-       port->msi_pages = __get_free_pages(GFP_KERNEL, 0);
-       if (!port->msi_pages)
-               return -ENOMEM;
-
-       msg_addr = virt_to_phys((void *)port->msi_pages);
-       pcie_write(port, 0x0, XILINX_PCIE_REG_MSIBASE1);
-       pcie_write(port, msg_addr, XILINX_PCIE_REG_MSIBASE2);
+       msg_addr = ALIGN_DOWN(virt_to_phys(port), SZ_4K);
+       pcie_write(port, upper_32_bits(msg_addr), XILINX_PCIE_REG_MSIBASE1);
+       pcie_write(port, lower_32_bits(msg_addr), XILINX_PCIE_REG_MSIBASE2);
 
        return 0;
 }