MIPS: generic: Convert SEAD-3 to a generic board

Convert the MIPS SEAD-3 board support to be a generic board, supported
by generic kernels.

Because the SEAD-3 boot protocol was defined long ago and we don't want
to force a switch to the UHI protocol, SEAD-3 is added as a legacy board
which is detected by reading the REVISION register. This may technically
not be a valid memory read & future work will include attempting to
handle that gracefully. In practice since SEAD-3 is the only legacy
board supported by the generic kernel so far the read will only happen
on SEAD-3 boards, and even once Malta is converted the same REVISION
register exists there too. Other boards such as Boston, Ci20 & Ci40 will
use the UHI boot protocol & thus not run any of the legacy board detect
functions.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14354/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 385 insertions, 0 deletions

diff --git a/arch/mips/generic/Kconfig b/arch/mips/generic/Kconfig
index baddb0646b23..a606b3f9196c 100644
--- a/arch/mips/generic/Kconfig
+++ b/arch/mips/generic/Kconfig
@@ -9,4 +9,11 @@ config LEGACY_BOARDS
 	  kernel is booted without being provided with an FDT via the UHI
 	  boot protocol.
 
+config LEGACY_BOARD_SEAD3
+	bool "Support MIPS SEAD-3 boards"
+	select LEGACY_BOARDS
+	help
+	  Enable this to include support for booting on MIPS SEAD-3 FPGA-based
+	  development boards, which boot using a legacy boot protocol.
+
 endif
diff --git a/arch/mips/generic/Makefile b/arch/mips/generic/Makefile
index 26e64207f7ad..7c66494151db 100644
--- a/arch/mips/generic/Makefile
+++ b/arch/mips/generic/Makefile
@@ -11,3 +11,5 @@
 obj-y += init.o
 obj-y += irq.o
 obj-y += proc.o
+
+obj-$(CONFIG_LEGACY_BOARD_SEAD3)	+= board-sead3.o
diff --git a/arch/mips/generic/board-sead3.c b/arch/mips/generic/board-sead3.c
new file mode 100644
index 000000000000..f4ae0584a33b
--- /dev/null
+++ b/arch/mips/generic/board-sead3.c
@@ -0,0 +1,376 @@
+/*
+ * 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: " fmt
+
+#include <linux/errno.h>
+#include <linux/libfdt.h>
+#include <linux/printk.h>
+
+#include <asm/fw/fw.h>
+#include <asm/io.h>
+#include <asm/machine.h>
+
+#define SEAD_CONFIG			CKSEG1ADDR(0x1b100110)
+#define SEAD_CONFIG_GIC_PRESENT		BIT(1)
+
+#define MIPS_REVISION			CKSEG1ADDR(0x1fc00010)
+#define MIPS_REVISION_MACHINE		(0xf << 4)
+#define MIPS_REVISION_MACHINE_SEAD3	(0x4 << 4)
+
+static __init bool sead3_detect(void)
+{
+	uint32_t rev;
+
+	rev = __raw_readl((void *)MIPS_REVISION);
+	return (rev & MIPS_REVISION_MACHINE) == MIPS_REVISION_MACHINE_SEAD3;
+}
+
+static __init int append_cmdline(void *fdt)
+{
+	int err, chosen_off;
+
+	/* find or add chosen node */
+	chosen_off = fdt_path_offset(fdt, "/chosen");
+	if (chosen_off == -FDT_ERR_NOTFOUND)
+		chosen_off = fdt_path_offset(fdt, "/chosen@0");
+	if (chosen_off == -FDT_ERR_NOTFOUND)
+		chosen_off = fdt_add_subnode(fdt, 0, "chosen");
+	if (chosen_off < 0) {
+		pr_err("Unable to find or add DT chosen node: %d\n",
+		       chosen_off);
+		return chosen_off;
+	}
+
+	err = fdt_setprop_string(fdt, chosen_off, "bootargs", fw_getcmdline());
+	if (err) {
+		pr_err("Unable to set bootargs property: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static __init int append_memory(void *fdt)
+{
+	unsigned long phys_memsize, memsize;
+	__be32 mem_array[2];
+	int err, mem_off;
+	char *var;
+
+	/* find memory size from the bootloader environment */
+	var = fw_getenv("memsize");
+	if (var) {
+		err = kstrtoul(var, 0, &phys_memsize);
+		if (err) {
+			pr_err("Failed to read memsize env variable '%s'\n",
+			       var);
+			return -EINVAL;
+		}
+	} else {
+		pr_warn("The bootloader didn't provide memsize: defaulting to 32MB\n");
+		phys_memsize = 32 << 20;
+	}
+
+	/* default to using all available RAM */
+	memsize = phys_memsize;
+
+	/* allow the user to override the usable memory */
+	var = strstr(arcs_cmdline, "memsize=");
+	if (var)
+		memsize = memparse(var + strlen("memsize="), NULL);
+
+	/* if the user says there's more RAM than we thought, believe them */
+	phys_memsize = max_t(unsigned long, phys_memsize, memsize);
+
+	/* find or add a memory node */
+	mem_off = fdt_path_offset(fdt, "/memory");
+	if (mem_off == -FDT_ERR_NOTFOUND)
+		mem_off = fdt_add_subnode(fdt, 0, "memory");
+	if (mem_off < 0) {
+		pr_err("Unable to find or add memory DT node: %d\n", mem_off);
+		return mem_off;
+	}
+
+	err = fdt_setprop_string(fdt, mem_off, "device_type", "memory");
+	if (err) {
+		pr_err("Unable to set memory node device_type: %d\n", err);
+		return err;
+	}
+
+	mem_array[0] = 0;
+	mem_array[1] = cpu_to_be32(phys_memsize);
+	err = fdt_setprop(fdt, mem_off, "reg", mem_array, sizeof(mem_array));
+	if (err) {
+		pr_err("Unable to set memory regs property: %d\n", err);
+		return err;
+	}
+
+	mem_array[0] = 0;
+	mem_array[1] = cpu_to_be32(memsize);
+	err = fdt_setprop(fdt, mem_off, "linux,usable-memory",
+			  mem_array, sizeof(mem_array));
+	if (err) {
+		pr_err("Unable to set linux,usable-memory property: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static __init int remove_gic(void *fdt)
+{
+	const unsigned int cpu_ehci_int = 2;
+	const unsigned int cpu_uart_int = 4;
+	const unsigned int cpu_eth_int = 6;
+	int gic_off, cpu_off, uart_off, eth_off, ehci_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;
+	}
+
+	uart_off = fdt_node_offset_by_compatible(fdt, -1, "ns16550a");
+	while (uart_off >= 0) {
+		err = fdt_setprop_u32(fdt, uart_off, "interrupts",
+				      cpu_uart_int);
+		if (err) {
+			pr_err("unable to set UART interrupts property: %d\n",
+			       err);
+			return err;
+		}
+
+		uart_off = fdt_node_offset_by_compatible(fdt, uart_off,
+							 "ns16550a");
+	}
+	if (uart_off != -FDT_ERR_NOTFOUND) {
+		pr_err("error searching for UART DT node: %d\n", uart_off);
+		return uart_off;
+	}
+
+	eth_off = fdt_node_offset_by_compatible(fdt, -1, "smsc,lan9115");
+	if (eth_off < 0) {
+		pr_err("unable to find ethernet DT node: %d\n", eth_off);
+		return eth_off;
+	}
+
+	err = fdt_setprop_u32(fdt, eth_off, "interrupts", cpu_eth_int);
+	if (err) {
+		pr_err("unable to set ethernet interrupts property: %d\n", err);
+		return err;
+	}
+
+	ehci_off = fdt_node_offset_by_compatible(fdt, -1, "generic-ehci");
+	if (ehci_off < 0) {
+		pr_err("unable to find EHCI DT node: %d\n", ehci_off);
+		return ehci_off;
+	}
+
+	err = fdt_setprop_u32(fdt, ehci_off, "interrupts", cpu_ehci_int);
+	if (err) {
+		pr_err("unable to set EHCI interrupts property: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static __init int serial_config(void *fdt)
+{
+	const char *yamontty, *mode_var;
+	char mode_var_name[9], path[18], parity;
+	unsigned int uart, baud, stop_bits;
+	bool hw_flow;
+	int chosen_off, err;
+
+	yamontty = fw_getenv("yamontty");
+	if (!yamontty || !strcmp(yamontty, "tty0")) {
+		uart = 0;
+	} else if (!strcmp(yamontty, "tty1")) {
+		uart = 1;
+	} else {
+		pr_warn("yamontty environment variable '%s' invalid\n",
+			yamontty);
+		uart = 0;
+	}
+
+	baud = stop_bits = 0;
+	parity = 0;
+	hw_flow = false;
+
+	snprintf(mode_var_name, sizeof(mode_var_name), "modetty%u", uart);
+	mode_var = fw_getenv(mode_var_name);
+	if (mode_var) {
+		while (mode_var[0] >= '0' && mode_var[0] <= '9') {
+			baud *= 10;
+			baud += mode_var[0] - '0';
+			mode_var++;
+		}
+		if (mode_var[0] == ',')
+			mode_var++;
+		if (mode_var[0])
+			parity = mode_var[0];
+		if (mode_var[0] == ',')
+			mode_var++;
+		if (mode_var[0])
+			stop_bits = mode_var[0] - '0';
+		if (mode_var[0] == ',')
+			mode_var++;
+		if (!strcmp(mode_var, "hw"))
+			hw_flow = true;
+	}
+
+	if (!baud)
+		baud = 38400;
+
+	if (parity != 'e' && parity != 'n' && parity != 'o')
+		parity = 'n';
+
+	if (stop_bits != 7 && stop_bits != 8)
+		stop_bits = 8;
+
+	WARN_ON(snprintf(path, sizeof(path), "uart%u:%u%c%u%s",
+			 uart, baud, parity, stop_bits,
+			 hw_flow ? "r" : "") >= sizeof(path));
+
+	/* find or add chosen node */
+	chosen_off = fdt_path_offset(fdt, "/chosen");
+	if (chosen_off == -FDT_ERR_NOTFOUND)
+		chosen_off = fdt_path_offset(fdt, "/chosen@0");
+	if (chosen_off == -FDT_ERR_NOTFOUND)
+		chosen_off = fdt_add_subnode(fdt, 0, "chosen");
+	if (chosen_off < 0) {
+		pr_err("Unable to find or add DT chosen node: %d\n",
+		       chosen_off);
+		return chosen_off;
+	}
+
+	err = fdt_setprop_string(fdt, chosen_off, "stdout-path", path);
+	if (err) {
+		pr_err("Unable to set stdout-path property: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static __init const void *sead3_fixup_fdt(const void *fdt,
+					  const void *match_data)
+{
+	static unsigned char fdt_buf[16 << 10] __initdata;
+	int err;
+
+	if (fdt_check_header(fdt))
+		panic("Corrupt DT");
+
+	/* if this isn't SEAD3, something went wrong */
+	BUG_ON(fdt_node_check_compatible(fdt, 0, "mti,sead-3"));
+
+	fw_init_cmdline();
+
+	err = fdt_open_into(fdt, fdt_buf, sizeof(fdt_buf));
+	if (err)
+		panic("Unable to open FDT: %d", err);
+
+	err = append_cmdline(fdt_buf);
+	if (err)
+		panic("Unable to patch FDT: %d", err);
+
+	err = append_memory(fdt_buf);
+	if (err)
+		panic("Unable to patch FDT: %d", err);
+
+	err = remove_gic(fdt_buf);
+	if (err)
+		panic("Unable to patch FDT: %d", err);
+
+	err = serial_config(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;
+}
+
+static __init unsigned int sead3_measure_hpt_freq(void)
+{
+	void __iomem *status_reg = (void __iomem *)0xbf000410;
+	unsigned int freq, orig, tick = 0;
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	orig = readl(status_reg) & 0x2;		      /* get original sample */
+	/* wait for transition */
+	while ((readl(status_reg) & 0x2) == orig)
+		;
+	orig = orig ^ 0x2;			      /* flip the bit */
+
+	write_c0_count(0);
+
+	/* wait 1 second (the sampling clock transitions every 10ms) */
+	while (tick < 100) {
+		/* wait for transition */
+		while ((readl(status_reg) & 0x2) == orig)
+			;
+		orig = orig ^ 0x2;			      /* flip the bit */
+		tick++;
+	}
+
+	freq = read_c0_count();
+
+	local_irq_restore(flags);
+
+	return freq;
+}
+
+extern char __dtb_sead3_begin[];
+
+MIPS_MACHINE(sead3) = {
+	.fdt = __dtb_sead3_begin,
+	.detect = sead3_detect,
+	.fixup_fdt = sead3_fixup_fdt,
+	.measure_hpt_freq = sead3_measure_hpt_freq,
+};