MIPS: SEAD3: Probe interrupt controllers using DT

Probe the CPU interrupt controller & optional Global Interrupt
Controller (GIC) using devicetree rather than platform code. Because the
bootloader on SEAD3 does not provide a device tree to the kernel & the
device tree is always built in, we patch out the GIC node during boot if
we detect that a GIC is not present in the system.

The appropriate IRQ domain is discovered by platform code setting up
device IRQ numbers temporarily. It will be removed by further patches
which move the devices towards being probed via device tree.

No behavioural change is intended by this patch.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Jacek Anaszewski <j.anaszewski@samsung.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14047/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 92 insertions, 0 deletions

diff --git a/arch/mips/mti-sead3/sead3-dtshim.c b/arch/mips/mti-sead3/sead3-dtshim.c
new file mode 100644
index 000000000000..3283a7e19a88
--- /dev/null
+++ b/arch/mips/mti-sead3/sead3-dtshim.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#define pr_fmt(fmt) "sead3-dtshim: " fmt
+
+#include <linux/errno.h>
+#include <linux/libfdt.h>
+#include <linux/printk.h>
+
+#include <asm/io.h>
+
+#define SEAD_CONFIG			CKSEG1ADDR(0x1b100110)
+#define SEAD_CONFIG_GIC_PRESENT		BIT(1)
+
+static unsigned char fdt_buf[16 << 10] __initdata;
+
+static int remove_gic(void *fdt)
+{
+	int gic_off, cpu_off, err;
+	uint32_t cfg, cpu_phandle;
+
+	/* leave the GIC node intact if a GIC is present */
+	cfg = __raw_readl((uint32_t *)SEAD_CONFIG);
+	if (cfg & SEAD_CONFIG_GIC_PRESENT)
+		return 0;
+
+	gic_off = fdt_node_offset_by_compatible(fdt, -1, "mti,gic");
+	if (gic_off < 0) {
+		pr_err("unable to find DT GIC node: %d\n", gic_off);
+		return gic_off;
+	}
+
+	err = fdt_nop_node(fdt, gic_off);
+	if (err) {
+		pr_err("unable to nop GIC node\n");
+		return err;
+	}
+
+	cpu_off = fdt_node_offset_by_compatible(fdt, -1,
+			"mti,cpu-interrupt-controller");
+	if (cpu_off < 0) {
+		pr_err("unable to find CPU intc node: %d\n", cpu_off);
+		return cpu_off;
+	}
+
+	cpu_phandle = fdt_get_phandle(fdt, cpu_off);
+	if (!cpu_phandle) {
+		pr_err("unable to get CPU intc phandle\n");
+		return -EINVAL;
+	}
+
+	err = fdt_setprop_u32(fdt, 0, "interrupt-parent", cpu_phandle);
+	if (err) {
+		pr_err("unable to set root interrupt-parent: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+void __init *sead3_dt_shim(void *fdt)
+{
+	int err;
+
+	if (fdt_check_header(fdt))
+		panic("Corrupt DT");
+
+	/* if this isn't SEAD3, leave the DT alone */
+	if (fdt_node_check_compatible(fdt, 0, "mti,sead-3"))
+		return fdt;
+
+	err = fdt_open_into(fdt, fdt_buf, sizeof(fdt_buf));
+	if (err)
+		panic("Unable to open FDT: %d", err);
+
+	err = remove_gic(fdt_buf);
+	if (err)
+		panic("Unable to patch FDT: %d", err);
+
+	err = fdt_pack(fdt_buf);
+	if (err)
+		panic("Unable to pack FDT: %d\n", err);
+
+	return fdt_buf;
+}