ARM: ixp4xx: Add device tree boot support

This adds a minimal support for booting IXP4xx systems
from device tree.

We have to add hacks to the QMGR, NPE and notably also
ethernet and watchdog drivers so that they don't crash
the platform: these drivers are unconditionally starting
to grab regions of statically remapped IO space with no
concern of the device model or other platforms.

We will go in and properly fix these drivers as we go
along but for now this hack gets us to a place where we
can start working on proper device tree support for these
platforms.

Signed-off-by: Linus Walleij <[e-mail]>

arch/arm/mach-ixp4xx/Kconfig

···
 
 comment "IXP4xx Platforms"
 
+config MACH_IXP4XX_OF
+	bool
+	prompt "Devce Tree IXP4xx boards"
+	default y
+	select ARM_APPENDED_DTB # Old Redboot bootloaders deployed
+	select I2C
+	select I2C_IOP3XX
+	select PCI
+	select SERIAL_OF_PLATFORM
+	select TIMER_OF
+	select USE_OF
+	help
+	  Say 'Y' here to support Device Tree-based IXP4xx platforms.
+
 config MACH_NSLU2
 	bool
 	prompt "Linksys NSLU2"

arch/arm/mach-ixp4xx/Makefile

···
 obj-pci-y	:=
 obj-pci-n	:=
 
+# Device tree platform
+obj-pci-$(CONFIG_MACH_IXP4XX_OF)	+= ixp4xx-of.o
+
 obj-pci-$(CONFIG_ARCH_IXDP4XX)		+= ixdp425-pci.o
 obj-pci-$(CONFIG_MACH_AVILA)		+= avila-pci.o
 obj-pci-$(CONFIG_MACH_IXDPG425)		+= ixdpg425-pci.o

arch/arm/mach-ixp4xx/ixp4xx-of.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IXP4xx Device Tree boot support
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+
+#include <asm/mach/arch.h>
+#include <asm/mach/map.h>
+
+#include <mach/hardware.h>
+#include <mach/ixp4xx-regs.h>
+
+static struct map_desc ixp4xx_of_io_desc[] __initdata = {
+	/*
+	 * This is needed for runtime system configuration checks,
+	 * such as reading if hardware so-and-so is present. This
+	 * could eventually be converted into a syscon once all boards
+	 * are converted to device tree.
+	 */
+	{
+		.virtual = IXP4XX_EXP_CFG_BASE_VIRT,
+		.pfn = __phys_to_pfn(IXP4XX_EXP_CFG_BASE_PHYS),
+		.length = SZ_4K,
+		.type = MT_DEVICE,
+	},
+#ifdef CONFIG_DEBUG_UART_8250
+	/* This is needed for LL-debug/earlyprintk/debug-macro.S */
+	{
+		.virtual = CONFIG_DEBUG_UART_VIRT,
+		.pfn = __phys_to_pfn(CONFIG_DEBUG_UART_PHYS),
+		.length = SZ_4K,
+		.type = MT_DEVICE,
+	},
+#endif
+};
+
+static void __init ixp4xx_of_map_io(void)
+{
+	iotable_init(ixp4xx_of_io_desc, ARRAY_SIZE(ixp4xx_of_io_desc));
+}
+
+/*
+ * We handle 4 differen SoC families. These compatible strings are enough
+ * to provide the core so that different boards can add their more detailed
+ * specifics.
+ */
+static const char *ixp4xx_of_board_compat[] = {
+	"intel,ixp42x",
+	"intel,ixp43x",
+	"intel,ixp45x",
+	"intel,ixp46x",
+	NULL,
+};
+
+DT_MACHINE_START(IXP4XX_DT, "IXP4xx (Device Tree)")
+	.map_io		= ixp4xx_of_map_io,
+	.dt_compat	= ixp4xx_of_board_compat,
+MACHINE_END

arch/arm/mach-ixp4xx/ixp4xx_npe.c

···
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <mach/npe.h>
 
 #define DEBUG_MSG			0
···
 {
 
 	int i, found = 0;
+
+	/* This driver does not work with device tree */
+	if (of_have_populated_dt())
+		return -ENODEV;
 
 	for (i = 0; i < NPE_COUNT; i++) {
 		struct npe *npe = &npe_tab[i];

arch/arm/mach-ixp4xx/ixp4xx_qmgr.c

···
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <mach/qmgr.h>
 
 #include "irqs.h"
···
 {
 	int i, err;
 	irq_handler_t handler1, handler2;
+
+	/* This driver does not work with device tree */
+	if (of_have_populated_dt())
+		return -ENODEV;
 
 	mem_res = request_mem_region(IXP4XX_QMGR_BASE_PHYS,
 				     IXP4XX_QMGR_REGION_SIZE,

drivers/net/ethernet/xscale/ixp4xx_eth.c

···
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/net_tstamp.h>
+#include <linux/of.h>
 #include <linux/phy.h>
 #include <linux/platform_device.h>
 #include <linux/ptp_classify.h>
···
 static int __init eth_init_module(void)
 {
 	int err;
+
+	/*
+	 * FIXME: we bail out on device tree boot but this really needs
+	 * to be fixed in a nicer way: this registers the MDIO bus before
+	 * even matching the driver infrastructure, we should only probe
+	 * detected hardware.
+	 */
+	if (of_have_populated_dt())
+		return -ENODEV;
 	if ((err = ixp4xx_mdio_register()))
 		return err;
 	return platform_driver_register(&ixp4xx_eth_driver);

drivers/watchdog/ixp4xx_wdt.c

···
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/miscdevice.h>
+#include <linux/of.h>
 #include <linux/watchdog.h>
 #include <linux/init.h>
 #include <linux/bitops.h>
···
 {
 	int ret;
 
+	/*
+	 * FIXME: we bail out on device tree boot but this really needs
+	 * to be fixed in a nicer way: this registers the MDIO bus before
+	 * even matching the driver infrastructure, we should only probe
+	 * detected hardware.
+	 */
+	if (of_have_populated_dt())
+		return -ENODEV;
 	if (!(read_cpuid_id() & 0xf) && !cpu_is_ixp46x()) {
 		pr_err("Rev. A0 IXP42x CPU detected - watchdog disabled\n");