xtensa: add device trees support

Device trees allow specification of hardware topology and device
parameters at runtime instead of hard-coding them in platform setup
code. This allows running single binary kernel on a range of compatible
boards.

New boot parameters tag BP_TAG_FDT is allocated and a pointer to flat
device tree is passed in it.

Note that current interrupt mapping scheme uses single cell for
interrupt identification. That means that IRQ numbers used in DTS must
be CPU internal IRQ numbers, not external. It is possible to extend
interrupt identification to two cells, and use second cell to tell
external IRQ numbers form internal. That would allow to use single DTS
on multiple boards with different mapping of external IRQ numbers.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

2 files changed, 128 insertions, 25 deletions

diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index e90d782..6f4f974 100644
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -19,6 +19,7 @@
 #include <linux/irq.h>
 #include <linux/kernel_stat.h>
 #include <linux/irqdomain.h>
+#include <linux/of.h>
 
 #include <asm/uaccess.h>
 #include <asm/platform.h>
@@ -199,8 +200,17 @@ void __init init_IRQ(void)
 	cached_irq_mask = 0;
 	set_sr(~0, intclear);
 
+#ifdef CONFIG_OF
+	/* The interrupt controller device node is mandatory */
+	intc = of_find_compatible_node(NULL, NULL, "xtensa,pic");
+	BUG_ON(!intc);
+
+	root_domain = irq_domain_add_linear(intc, NR_IRQS,
+			&xtensa_irq_domain_ops, NULL);
+#else
 	root_domain = irq_domain_add_legacy(intc, NR_IRQS, 0, 0,
 			&xtensa_irq_domain_ops, NULL);
+#endif
 	irq_set_default_host(root_domain);
 
 	variant_init_irq();
diff --git a/arch/xtensa/kernel/setup.c b/arch/xtensa/kernel/setup.c
index 4521761..64d80e4 100644
--- a/arch/xtensa/kernel/setup.c
+++ b/arch/xtensa/kernel/setup.c
@@ -22,6 +22,11 @@
 #include <linux/bootmem.h>
 #include <linux/kernel.h>
 
+#ifdef CONFIG_OF
+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+#endif
+
 #if defined(CONFIG_VGA_CONSOLE) || defined(CONFIG_DUMMY_CONSOLE)
 # include <linux/console.h>
 #endif
@@ -65,6 +70,11 @@ int initrd_is_mapped = 0;
 extern int initrd_below_start_ok;
 #endif
 
+#ifdef CONFIG_OF
+extern u32 __dtb_start[];
+void *dtb_start = __dtb_start;
+#endif
+
 unsigned char aux_device_present;
 extern unsigned long loops_per_jiffy;
 
@@ -84,6 +94,8 @@ extern void init_mmu(void);
 static inline void init_mmu(void) { }
 #endif
 
+extern int mem_reserve(unsigned long, unsigned long, int);
+extern void bootmem_init(void);
 extern void zones_init(void);
 
 /*
@@ -105,28 +117,33 @@ typedef struct tagtable {
 
 /* parse current tag */
 
-static int __init parse_tag_mem(const bp_tag_t *tag)
+static int __init add_sysmem_bank(unsigned long type, unsigned long start,
+		unsigned long end)
 {
-	meminfo_t *mi = (meminfo_t*)(tag->data);
-
-	if (mi->type != MEMORY_TYPE_CONVENTIONAL)
-		return -1;
-
 	if (sysmem.nr_banks >= SYSMEM_BANKS_MAX) {
 		printk(KERN_WARNING
-		       "Ignoring memory bank 0x%08lx size %ldKB\n",
-		       (unsigned long)mi->start,
-		       (unsigned long)mi->end - (unsigned long)mi->start);
+				"Ignoring memory bank 0x%08lx size %ldKB\n",
+				start, end - start);
 		return -EINVAL;
 	}
-	sysmem.bank[sysmem.nr_banks].type  = mi->type;
-	sysmem.bank[sysmem.nr_banks].start = PAGE_ALIGN(mi->start);
-	sysmem.bank[sysmem.nr_banks].end   = mi->end & PAGE_MASK;
+	sysmem.bank[sysmem.nr_banks].type  = type;
+	sysmem.bank[sysmem.nr_banks].start = PAGE_ALIGN(start);
+	sysmem.bank[sysmem.nr_banks].end   = end & PAGE_MASK;
 	sysmem.nr_banks++;
 
 	return 0;
 }
 
+static int __init parse_tag_mem(const bp_tag_t *tag)
+{
+	meminfo_t *mi = (meminfo_t *)(tag->data);
+
+	if (mi->type != MEMORY_TYPE_CONVENTIONAL)
+		return -1;
+
+	return add_sysmem_bank(mi->type, mi->start, mi->end);
+}
+
 __tagtable(BP_TAG_MEMORY, parse_tag_mem);
 
 #ifdef CONFIG_BLK_DEV_INITRD
@@ -143,12 +160,31 @@ static int __init parse_tag_initrd(const bp_tag_t* tag)
 
 __tagtable(BP_TAG_INITRD, parse_tag_initrd);
 
+#ifdef CONFIG_OF
+
+static int __init parse_tag_fdt(const bp_tag_t *tag)
+{
+	dtb_start = (void *)(tag->data[0]);
+	return 0;
+}
+
+__tagtable(BP_TAG_FDT, parse_tag_fdt);
+
+void __init early_init_dt_setup_initrd_arch(unsigned long start,
+		unsigned long end)
+{
+	initrd_start = (void *)__va(start);
+	initrd_end = (void *)__va(end);
+	initrd_below_start_ok = 1;
+}
+
+#endif /* CONFIG_OF */
+
 #endif /* CONFIG_BLK_DEV_INITRD */
 
 static int __init parse_tag_cmdline(const bp_tag_t* tag)
 {
-	strncpy(command_line, (char*)(tag->data), COMMAND_LINE_SIZE);
-	command_line[COMMAND_LINE_SIZE - 1] = '\0';
+	strlcpy(command_line, (char *)(tag->data), COMMAND_LINE_SIZE);
 	return 0;
 }
 
@@ -186,6 +222,58 @@ static int __init parse_bootparam(const bp_tag_t* tag)
 	return 0;
 }
 
+#ifdef CONFIG_OF
+
+void __init early_init_dt_add_memory_arch(u64 base, u64 size)
+{
+	size &= PAGE_MASK;
+	add_sysmem_bank(MEMORY_TYPE_CONVENTIONAL, base, base + size);
+}
+
+void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
+{
+	return __alloc_bootmem(size, align, 0);
+}
+
+void __init early_init_devtree(void *params)
+{
+	/* Setup flat device-tree pointer */
+	initial_boot_params = params;
+
+	/* Retrieve various informations from the /chosen node of the
+	 * device-tree, including the platform type, initrd location and
+	 * size, TCE reserve, and more ...
+	 */
+	if (!command_line[0])
+		of_scan_flat_dt(early_init_dt_scan_chosen, command_line);
+
+	/* Scan memory nodes and rebuild MEMBLOCKs */
+	of_scan_flat_dt(early_init_dt_scan_root, NULL);
+	if (sysmem.nr_banks == 0)
+		of_scan_flat_dt(early_init_dt_scan_memory, NULL);
+}
+
+static void __init copy_devtree(void)
+{
+	void *alloc = early_init_dt_alloc_memory_arch(
+			be32_to_cpu(initial_boot_params->totalsize), 0);
+	if (alloc) {
+		memcpy(alloc, initial_boot_params,
+				be32_to_cpu(initial_boot_params->totalsize));
+		initial_boot_params = alloc;
+	}
+}
+
+static int __init xtensa_device_probe(void)
+{
+	of_platform_populate(NULL, NULL, NULL, NULL);
+	return 0;
+}
+
+device_initcall(xtensa_device_probe);
+
+#endif /* CONFIG_OF */
+
 /*
  * Initialize architecture. (Early stage)
  */
@@ -194,14 +282,14 @@ void __init init_arch(bp_tag_t *bp_start)
 {
 	sysmem.nr_banks = 0;
 
-#ifdef CONFIG_CMDLINE_BOOL
-	strcpy(command_line, default_command_line);
-#endif
-
 	/* Parse boot parameters */
 
         if (bp_start)
-	  parse_bootparam(bp_start);
+		parse_bootparam(bp_start);
+
+#ifdef CONFIG_OF
+	early_init_devtree(dtb_start);
+#endif
 
 	if (sysmem.nr_banks == 0) {
 		sysmem.nr_banks = 1;
@@ -210,6 +298,11 @@ void __init init_arch(bp_tag_t *bp_start)
 				     + PLATFORM_DEFAULT_MEM_SIZE;
 	}
 
+#ifdef CONFIG_CMDLINE_BOOL
+	if (!command_line[0])
+		strlcpy(command_line, default_command_line, COMMAND_LINE_SIZE);
+#endif
+
 	/* Early hook for platforms */
 
 	platform_init(bp_start);
@@ -355,11 +448,7 @@ void __init check_s32c1i(void)
 
 void __init setup_arch(char **cmdline_p)
 {
-	extern int mem_reserve(unsigned long, unsigned long, int);
-	extern void bootmem_init(void);
-
-	memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
-	boot_command_line[COMMAND_LINE_SIZE-1] = '\0';
+	strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
 	*cmdline_p = command_line;
 
 	check_s32c1i();
@@ -395,8 +484,12 @@ void __init setup_arch(char **cmdline_p)
 
 	bootmem_init();
 
-	platform_setup(cmdline_p);
+#ifdef CONFIG_OF
+	copy_devtree();
+	unflatten_device_tree();
+#endif
 
+	platform_setup(cmdline_p);
 
 	paging_init();
 	zones_init();