pci: xilinx: Enable MMIO region

The host bridge MMIO region is disabled by default due to which MMIO
accesses cause an exception. Fix it by setting the bridge enable bit.
This change is ported from the linux pcie-xilinx driver.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20231116165103.140968-3-mchitale@ventanamicro.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/drivers/pci/pcie_xilinx.c b/drivers/pci/pcie_xilinx.c
index fdc9b08..3db460b 100644
--- a/drivers/pci/pcie_xilinx.c
+++ b/drivers/pci/pcie_xilinx.c
@@ -24,6 +24,8 @@
 /* Register definitions */
 #define XILINX_PCIE_REG_PSCR		0x144
 #define XILINX_PCIE_REG_PSCR_LNKUP	BIT(11)
+#define XILINX_PCIE_REG_RPSC		0x148
+#define XILINX_PCIE_REG_RPSC_BEN	BIT(0)
 
 /**
  * pcie_xilinx_link_up() - Check whether the PCIe link is up
@@ -141,6 +143,7 @@
 	struct xilinx_pcie *pcie = dev_get_priv(dev);
 	fdt_addr_t addr;
 	fdt_size_t size;
+	u32 rpsc;
 
 	addr = dev_read_addr_size(dev, &size);
 	if (addr == FDT_ADDR_T_NONE)
@@ -150,6 +153,11 @@
 	if (IS_ERR(pcie->cfg_base))
 		return PTR_ERR(pcie->cfg_base);
 
+	/* Enable the Bridge enable bit */
+	rpsc = __raw_readl(pcie->cfg_base + XILINX_PCIE_REG_RPSC);
+	rpsc |= XILINX_PCIE_REG_RPSC_BEN;
+	__raw_writel(rpsc, pcie->cfg_base + XILINX_PCIE_REG_RPSC);
+
 	return 0;
 }