PCI: tango: Add Sigma Designs Tango SMP8759 PCIe host bridge support

This driver is required to work around several hardware bugs in the PCIe
controller.

The SMP8759 does not support legacy interrupts or IO space.

Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
[bhelgaas: add CONFIG_BROKEN dependency, various cleanups]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

3 files changed, 156 insertions, 0 deletions

diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
index 7f47cd5e10a5..8e54115681d8 100644
--- a/drivers/pci/host/Kconfig
+++ b/drivers/pci/host/Kconfig
@@ -180,6 +180,20 @@ config PCIE_ROCKCHIP
 	  There is 1 internal PCIe port available to support GEN2 with
 	  4 slots.
 
+config PCIE_TANGO_SMP8759
+	bool "Tango SMP8759 PCIe controller (DANGEROUS)"
+	depends on ARCH_TANGO && PCI_MSI && OF
+	depends on BROKEN
+	select PCI_HOST_COMMON
+	help
+	  Say Y here to enable PCIe controller support for Sigma Designs
+	  Tango SMP8759-based systems.
+
+	  Note: The SMP8759 controller multiplexes PCI config and MMIO
+	  accesses, and Linux doesn't provide a way to serialize them.
+	  This can lead to data corruption if drivers perform concurrent
+	  config and MMIO accesses.
+
 config VMD
 	depends on PCI_MSI && X86_64 && SRCU
 	tristate "Intel Volume Management Device Driver"
diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
index cab879578003..eb48aa6377c8 100644
--- a/drivers/pci/host/Makefile
+++ b/drivers/pci/host/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_PCIE_IPROC_BCMA) += pcie-iproc-bcma.o
 obj-$(CONFIG_PCIE_ALTERA) += pcie-altera.o
 obj-$(CONFIG_PCIE_ALTERA_MSI) += pcie-altera-msi.o
 obj-$(CONFIG_PCIE_ROCKCHIP) += pcie-rockchip.o
+obj-$(CONFIG_PCIE_TANGO_SMP8759) += pcie-tango.o
 obj-$(CONFIG_VMD) += vmd.o
 
 # The following drivers are for devices that use the generic ACPI
diff --git a/drivers/pci/host/pcie-tango.c b/drivers/pci/host/pcie-tango.c
new file mode 100644
index 000000000000..6bbb81f06a53
--- /dev/null
+++ b/drivers/pci/host/pcie-tango.c
@@ -0,0 +1,141 @@
+#include <linux/pci-ecam.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+
+#define SMP8759_MUX		0x48
+#define SMP8759_TEST_OUT	0x74
+
+struct tango_pcie {
+	void __iomem *base;
+};
+
+static int smp8759_config_read(struct pci_bus *bus, unsigned int devfn,
+			       int where, int size, u32 *val)
+{
+	struct pci_config_window *cfg = bus->sysdata;
+	struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
+	int ret;
+
+	/* Reads in configuration space outside devfn 0 return garbage */
+	if (devfn != 0)
+		return PCIBIOS_FUNC_NOT_SUPPORTED;
+
+	/*
+	 * PCI config and MMIO accesses are muxed.  Linux doesn't have a
+	 * mutual exclusion mechanism for config vs. MMIO accesses, so
+	 * concurrent accesses may cause corruption.
+	 */
+	writel_relaxed(1, pcie->base + SMP8759_MUX);
+	ret = pci_generic_config_read(bus, devfn, where, size, val);
+	writel_relaxed(0, pcie->base + SMP8759_MUX);
+
+	return ret;
+}
+
+static int smp8759_config_write(struct pci_bus *bus, unsigned int devfn,
+				int where, int size, u32 val)
+{
+	struct pci_config_window *cfg = bus->sysdata;
+	struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
+	int ret;
+
+	writel_relaxed(1, pcie->base + SMP8759_MUX);
+	ret = pci_generic_config_write(bus, devfn, where, size, val);
+	writel_relaxed(0, pcie->base + SMP8759_MUX);
+
+	return ret;
+}
+
+static struct pci_ecam_ops smp8759_ecam_ops = {
+	.bus_shift	= 20,
+	.pci_ops	= {
+		.map_bus	= pci_ecam_map_bus,
+		.read		= smp8759_config_read,
+		.write		= smp8759_config_write,
+	}
+};
+
+static int tango_pcie_link_up(struct tango_pcie *pcie)
+{
+	void __iomem *test_out = pcie->base + SMP8759_TEST_OUT;
+	int i;
+
+	writel_relaxed(16, test_out);
+	for (i = 0; i < 10; ++i) {
+		u32 ltssm_state = readl_relaxed(test_out) >> 8;
+		if ((ltssm_state & 0x1f) == 0xf) /* L0 */
+			return 1;
+		usleep_range(3000, 4000);
+	}
+
+	return 0;
+}
+
+static int tango_pcie_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct tango_pcie *pcie;
+	struct resource *res;
+	int ret;
+
+	dev_warn(dev, "simultaneous PCI config and MMIO accesses may cause data corruption\n");
+	add_taint(TAINT_CRAP, LOCKDEP_STILL_OK);
+
+	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
+	if (!pcie)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	pcie->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(pcie->base))
+		return PTR_ERR(pcie->base);
+
+	platform_set_drvdata(pdev, pcie);
+
+	if (!tango_pcie_link_up(pcie))
+		return -ENODEV;
+
+	return pci_host_common_probe(pdev, &smp8759_ecam_ops);
+}
+
+static const struct of_device_id tango_pcie_ids[] = {
+	{ .compatible = "sigma,smp8759-pcie" },
+	{ },
+};
+
+static struct platform_driver tango_pcie_driver = {
+	.probe	= tango_pcie_probe,
+	.driver	= {
+		.name = KBUILD_MODNAME,
+		.of_match_table = tango_pcie_ids,
+		.suppress_bind_attrs = true,
+	},
+};
+builtin_platform_driver(tango_pcie_driver);
+
+/*
+ * The root complex advertises the wrong device class.
+ * Header Type 1 is for PCI-to-PCI bridges.
+ */
+static void tango_fixup_class(struct pci_dev *dev)
+{
+	dev->class = PCI_CLASS_BRIDGE_PCI << 8;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0024, tango_fixup_class);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0028, tango_fixup_class);
+
+/*
+ * The root complex exposes a "fake" BAR, which is used to filter
+ * bus-to-system accesses.  Only accesses within the range defined by this
+ * BAR are forwarded to the host, others are ignored.
+ *
+ * By default, the DMA framework expects an identity mapping, and DRAM0 is
+ * mapped at 0x80000000.
+ */
+static void tango_fixup_bar(struct pci_dev *dev)
+{
+	dev->non_compliant_bars = true;
+	pci_write_config_dword(dev, PCI_BASE_ADDRESS_0, 0x80000000);
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0024, tango_fixup_bar);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0028, tango_fixup_bar);