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Re: [PATCH 2/2 RFC] of/mips: Add device tree support to MIPS

To: Grant Likely <grant.likely@secretlab.ca>, dediao@cisco.com
Subject: Re: [PATCH 2/2 RFC] of/mips: Add device tree support to MIPS
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 18 Oct 2010 13:50:56 -0700
Cc: benh@kernel.crashing.org, ralf@linux-mips.org, linux-mips@linux-mips.org, monstr@monstr.eu, dvomlehn@cisco.com, devicetree-discuss@lists.ozlabs.org
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Although I tested this patch, and it compiles, I have a few more comments now that I have studied it.

Basically, it looks like most of the code in arch/mips/kernel/prom.c is not generic to MIPS, but instead highly specific to some platform (perhaps PowerTV).

On 10/12/2010 11:48 PM, Grant Likely wrote:
From: Dezhong Diao<dediao@cisco.com>

Add the ability to enable CONFIG_OF on the MIPS architecture.

Signed-off-by: Dezhong Diao<dediao@cisco.com>
[grant.likely@secretlab.ca: cleared out obsolete hooks,
        removed ARCH_HAS_DEVTREE_MEM from being manually selected,
        remove __init tags from header file]
Signed-off-by: Grant Likely<grant.likely@secretlab.ca>
Cc: linux-mips@linux-mips.org
Cc: David Daney<ddaney@caviumnetworks.com>
Cc: David VomLehn<dvomlehn@cisco.com>
---

I've not tested this on anything, but I picked up the MIPS device tree
patch written by Dezhong and updated it to match the changes in
mainline.  I also half-heartedly tried to rebase the powertv support
patch, didn't get very far due to the refactoring in
arch/mips/powertv/memory.c

Anyway, please take a look and give it a spin.  If it looks good, then
I can add it into my -next branch.

g.

  arch/mips/Kconfig            |   13 ++++
  arch/mips/include/asm/prom.h |   35 +++++++++++
  arch/mips/kernel/Makefile    |    2 +
  arch/mips/kernel/prom.c      |  135 ++++++++++++++++++++++++++++++++++++++++++
  arch/mips/kernel/setup.c     |    2 +
  5 files changed, 187 insertions(+), 0 deletions(-)
  create mode 100644 arch/mips/include/asm/prom.h
  create mode 100644 arch/mips/kernel/prom.c

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 3ad59dd..15e364d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2107,6 +2107,19 @@ config SECCOMP

          If unsure, say Y. Only embedded should say N here.

+config USE_OF
+       bool "Flattened Device Tree support"
+       select OF
+       select OF_FLATTREE
+       help
+         Include support for flattened device tree machine descriptions.
+
+config ARCH_HAS_DEVTREE_MEM
+       bool
+       depends on OF
+       help
+         The user has a customized function to parse memory nodes.
+
  endmenu


These Kconfig items should only be selectable if OF is truly supported. Hardwiring ARCH_HAS_DEVTREE_MEM to USE_OF at this global level doesn't seem quite right either. I think it is conceivable that we would want USE_OF without ARCH_HAS_DEVTREE_MEM.


  config LOCKDEP_SUPPORT
diff --git a/arch/mips/include/asm/prom.h b/arch/mips/include/asm/prom.h
new file mode 100644
index 0000000..23f8237
--- /dev/null
+++ b/arch/mips/include/asm/prom.h
@@ -0,0 +1,35 @@
+/*
+ *  arch/mips/include/asm/prom.h
+ *
+ *  Copyright (C) 2010 Cisco Systems Inc.<dediao@cisco.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#ifndef __ASM_MIPS_PROM_H
+#define __ASM_MIPS_PROM_H
+
+#ifdef CONFIG_OF
+#include<linux/init.h>
+
+#include<asm/setup.h>
+#include<asm/irq.h>
+#include<asm/bootinfo.h>
+
+/* which is compatible with the flattened device tree (FDT) */
+#define cmd_line arcs_cmdline
+
+extern int early_init_dt_scan_memory_arch(unsigned long node,
+       const char *uname, int depth, void *data);
+
+extern int reserve_mem_mach(unsigned long addr, unsigned long size);
+extern void free_mem_mach(unsigned long addr, unsigned long size);
+
+extern void __init device_tree_init(void);
+#else /* CONFIG_OF */
+static inline void __init device_tree_init(void) { }
+#endif /* CONFIG_OF */
+
+#endif /* _ASM_MIPS_PROM_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 06f8482..8088498 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -96,6 +96,8 @@ obj-$(CONFIG_KEXEC)           += machine_kexec.o 
relocate_kernel.o
  obj-$(CONFIG_EARLY_PRINTK)    += early_printk.o
  obj-$(CONFIG_SPINLOCK_TEST)   += spinlock_test.o

+obj-$(CONFIG_OF)               += prom.o
+
  CFLAGS_cpu-bugs64.o   = $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc 
/dev/null>/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)

  obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT) += 8250-platform.o
diff --git a/arch/mips/kernel/prom.c b/arch/mips/kernel/prom.c
new file mode 100644
index 0000000..6378834
--- /dev/null
+++ b/arch/mips/kernel/prom.c
@@ -0,0 +1,135 @@
+/*
+ *  linux/arch/mips/kernel/prom.c
+ *
+ *  Copyright (C) 2010 Cisco Systems Inc.<dediao@cisco.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include<linux/init.h>
+#include<linux/module.h>
+#include<linux/errno.h>
+#include<linux/types.h>
+#include<linux/bootmem.h>
+#include<linux/initrd.h>
+#include<linux/debugfs.h>
+#include<linux/of.h>
+#include<linux/of_fdt.h>
+#include<linux/of_irq.h>
+#include<linux/of_platform.h>
+
+#include<asm/page.h>
+#include<asm/prom.h>
+
+#ifndef CONFIG_ARCH_HAS_DEVTREE_MEM
+int __init early_init_dt_scan_memory_arch(unsigned long node,
+                                         const char *uname, int depth,
+                                         void *data)
+{
+       return early_init_dt_scan_memory(node, uname, depth, data);
+}
+
+void __init early_init_dt_add_memory_arch(u64 base, u64 size)
+{
+       return add_memory_region(base, size, BOOT_MEM_RAM);
+}
+
+int __init reserve_mem_mach(unsigned long addr, unsigned long size)
+{
+       return reserve_bootmem(addr, size, BOOTMEM_DEFAULT);
+}
+
+void __init free_mem_mach(unsigned long addr, unsigned long size)
+{
+       return free_bootmem(addr, size);
+}
+#endif
+
+u64 __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
+{
+       return virt_to_phys(
+               __alloc_bootmem(size, align, __pa(MAX_DMA_ADDRESS))
+               );
+}
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init early_init_dt_setup_initrd_arch(unsigned long start,
+                                           unsigned long end)
+{
+       initrd_start = (unsigned long)__va(start);
+       initrd_end = (unsigned long)__va(end);
+       initrd_below_start_ok = 1;
+}
+#endif
+
+/*
+ * irq_create_of_mapping - Hook to resolve OF irq specifier into a Linux irq#
+ *
+ * Currently the mapping mechanism is trivial; simple flat hwirq numbers are
+ * mapped 1:1 onto Linux irq numbers.  Cascaded irq controllers are not
+ * supported.
+ */
+unsigned int irq_create_of_mapping(struct device_node *controller,
+                                  const u32 *intspec, unsigned int intsize)
+{
+       return intspec[0];
+}
+EXPORT_SYMBOL_GPL(irq_create_of_mapping);
+

This mapping function depends on the interrupt controller architecture. It is not at all a good fit for what I want to do on Octeon. We have a hierarchy of interrupt mapping that is best described by a two level tree, so has '#interrupt-cells = <2>;'. We definitely need a different implementation than this.

+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, and more ...
+        */
+       of_scan_flat_dt(early_init_dt_scan_chosen, NULL);
+
+       /* Scan memory nodes */
+       of_scan_flat_dt(early_init_dt_scan_root, NULL);
+       of_scan_flat_dt(early_init_dt_scan_memory_arch, NULL);
+}
+
+void __init device_tree_init(void)
+{
+       unsigned long base, size;
+
+       if (!initial_boot_params)
+               return;
+
+       base = virt_to_phys((void *)initial_boot_params);
+       size = initial_boot_params->totalsize;
+
+       /* Before we do anything, lets reserve the dt blob */
+       reserve_mem_mach(base, size);
+
+       unflatten_device_tree();
+
+       /* free the space reserved for the dt blob */
+       free_mem_mach(base, size);
+}
+
+#if defined(CONFIG_DEBUG_FS)&&  defined(DEBUG)
+static struct dentry *of_debugfs_root;
+static struct debugfs_blob_wrapper flat_dt_blob;
+
+static int __init export_flat_device_tree(void)
+{
+       struct dentry *d;
+
+       flat_dt_blob.data = initial_boot_params;
+       flat_dt_blob.size = initial_boot_params->totalsize;
+
+       d = debugfs_create_blob("flat-device-tree", S_IFREG | S_IRUSR,
+                               of_debugfs_root,&flat_dt_blob);
+       if (!d)
+               return 1;
+
+       return 0;
+}
+device_initcall(export_flat_device_tree);

This debugfs bit will fail. of_debugfs_root is never initialized that I can see.


+#endif
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 85aef3f..a6b900f 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -31,6 +31,7 @@
  #include<asm/setup.h>
  #include<asm/smp-ops.h>
  #include<asm/system.h>
+#include<asm/prom.h>

  struct cpuinfo_mips cpu_data[NR_CPUS] __read_mostly;

@@ -487,6 +488,7 @@ static void __init arch_mem_init(char **cmdline_p)
        }

        bootmem_init();
+       device_tree_init();
        sparse_init();
        paging_init();
  }




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