2014-12-23 接着调，3.0和3.15 用不用fdt区别挺大的

上次是因为fdt或者atags传的不对，后来内核编译成支持fdt的，也把fdt传进去了，但和kernel里编译的machine_desc对应不上。fdt的用法必须要看了。不过现在没去看这个，直接把kernel里的machine_desc直接给过去了，因为这个kernel里只有一个arndale的machine_desc。

 877 void __init setup_arch(char **cmdline_p)
 878 {
 879     struct machine_desc *mdesc;
 880
 881     unwind_init();
 882
 883     setup_processor();
 884 // uty: test
 885 //mdesc = setup_machine_fdt(__atags_pointer);
 886 //if (!mdesc)
 887 // mdesc = setup_machine_tags(machine_arch_type);
 888     mdesc = __arch_info_begin;
 889     machine_desc = mdesc;
 890     machine_name = mdesc->name;

888行，直接赋值machine_desc。
这部分就跑过去了，还没看到什么问题，不知道因为启用了fdt，kernel后面还会不会出和这个有关的问题。
后面跑没多远，又停了，加了些输出。
跑到这里

(XEN) 3... 2... 1...
(XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch input to Xen)
(XEN) Freed 264kB init memory.
(XEN) DOM0: Uncompressing Linux... done, booting the kernel.
(XEN) DOM0: <6>Initializing cgroup subsys cpu
(XEN) DOM0: <5>Linux version 3.0.31-g3370a7c-dirty ([e-mail]) (gcc version 4.6.x-google 20120106 (prerelease) (GCC) ) #12
(XEN) DOM0:  SMP PREEMPT Wed Dec 17 09:32:10 CST 2014
(XEN) DOM0: CPU: ARMv7 Processor [410fc0f4] revision 4 (ARMv7), cr=10c5387d
(XEN) DOM0: CPU: VIPT nonaliasing data cache, VIPT aliasing instruction cache
(XEN) DOM0: Memory policy: ECC disabled, Data cache writealloc
(XEN) DOM0: uty: build_mem_type_table end
(XEN) DOM0: uty: build_mem_type_table end
(XEN) DOM0: uty: prepare_page_table end
(XEN) DOM0: uty: prepare_page_table end
(XEN) DOM0: uty: map_lowmem end
(XEN) DOM0: uty: map_lowmem end

出错在 arch\arm\mm\mmu.c devicemaps_init(mdesc);
确实，这里跑不过去是正常的。。

922 /*
923 * Set up device the mappings. Since we clear out the page tables for all
924 * mappings above VMALLOC_END, we will remove any debug device mappings.
925 * This means you have to be careful how you debug this function, or any
926 * called function. This means you can't use any function or debugging
927 * method which may touch any device, otherwise the kernel _will_ crash.
928 */
929 static void __init devicemaps_init(struct machine_desc *mdesc)
930 {
931         struct map_desc map;
932         unsigned long addr;
933
934 /*
935 * Allocate the vector page early.
936 */
937         vectors_page = early_alloc(PAGE_SIZE);
938
939 for (addr = VMALLOC_END; addr; addr += PMD_SIZE)
940                 pmd_clear(pmd_off_k(addr));
941
942 /*
943 * Map the kernel if it is XIP.
944 * It is always first in the modulearea.
945 */
946 #ifdef CONFIG_XIP_KERNEL
947         map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK);
948         map.virtual = MODULES_VADDR;
949         map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;
950         map.type = MT_ROM;
951         create_mapping(&map);
952 #endif
953
954 /*
955 * Map the cache flushing regions.
956 */
957 #ifdef FLUSH_BASE
958         map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS);
959         map.virtual = FLUSH_BASE;
960         map.length = SZ_1M;
961         map.type = MT_CACHECLEAN;
962         create_mapping(&map);
963 #endif
964 #ifdef FLUSH_BASE_MINICACHE
965         map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS + SZ_1M);
966         map.virtual = FLUSH_BASE_MINICACHE;
967         map.length = SZ_1M;
968         map.type = MT_MINICLEAN;
969         create_mapping(&map);
970 #endif
971
972 /*
973 * Create a mapping for the machine vectors at the high-vectors
974 * location (0xffff0000). If we aren't using high-vectors, also
975 * create a mapping at the low-vectors virtual address.
976 */
977         map.pfn = __phys_to_pfn(virt_to_phys(vectors_page));
978         map.virtual = 0xffff0000;
979         map.length = PAGE_SIZE;
980         map.type = MT_HIGH_VECTORS;
981         create_mapping(&map);
982
983 if (!vectors_high()) {
984                 map.virtual = 0;
985                 map.type = MT_LOW_VECTORS;
986                 create_mapping(&map);
987 }
988
989 /*
990 * Ask the machine support to map in the statically mapped devices.
991 */
992 if (mdesc->map_io)
993                 mdesc->map_io();
994
995 /*
996 * Finally flush the caches and tlb to ensure that we're in a
997 * consistent state wrt the writebuffer. This also ensures that
998 * any write-allocated cache lines in the vector page are written
999 * back. After this point, we can start to touch devices again.
1000 */
1001         local_flush_tlb_all();
1002         flush_cache_all();
1003 }

chinaunix贴代码怎么烂成这样。。。
这个函数是初始化所有IO地址的。开头的注释说的挺郁闷，不能调式什么的，因为一上来就把VMALLOC_END后的也表全删了。不过printk应该还能用，因为create_mapping里就用了，奇怪create_mapping里不会用到任何io吗？early_print应该可以用，因为是直接用物理地址的。试试就知道了。
这里面还调用了machine_desc->map_io()。因为xen是对内存布局作了修改的，本来是通过修改fdt再传给linux。比如内存已经不是0x40000000开始了，而是从0x80000000开始的512MB，并且这个地址的确定也是xen动态生成的。

1648 static void __init arndale_fixup(struct machine_desc *desc,
1649                 struct tag *tags, char **cmdline,
1650                 struct meminfo *mi)
1651 {
1652     mi->bank[0].start = 0x40000000;
1653     mi->bank[0].size = 1024 * SZ_1M;
1654
1655     mi->bank[1].start = 0x80000000;
1656     mi->bank[1].size = 1023 * SZ_1M;
1657
1658     mi->nr_banks = 2;
1659 }

这里就需要改，因为0x40000000不在是内存，而linux不知道，再访问这里就会出错。
而map_io里，也要看看xen改了哪里，哪里不能碰。至少uart是不能初始化了，因为xen没有把uart的物理地址映射到dom0里。

1285 static void __init arndale_map_io(void)
1286 {
1287     clk_xxti.rate = 24000000;
1288     s5p_init_io(NULL, 0, S5P_VA_CHIPID);
1289     s3c24xx_init_clocks(24000000);
1290     s3c24xx_init_uarts(arndale_uartcfgs, ARRAY_SIZE(arndale_uartcfgs));
1291     exynos_reserve_mem();
1292 }

s5p_init_io(NULL, 0, S5P_VA_CHIPID); 里面初始化minimal的io，这部分在arch/arm/plat-s5p/cpu.c里

99 /* minimal IO mapping */
100
101 static struct map_desc s5p_iodesc[] __initdata = {
102 {
103 .virtual = (unsigned long)S5P_VA_CHIPID,
104 .pfn = __phys_to_pfn(S5P_PA_CHIPID),
105 .length = SZ_4K,
106 .type = MT_DEVICE,
107 }, {
108 .virtual = (unsigned long)S3C_VA_SYS,
109 .pfn = __phys_to_pfn(S5P_PA_SYSCON),
110 .length = SZ_64K,
111 .type = MT_DEVICE,
112 }, {
113 .virtual = (unsigned long)S3C_VA_TIMER,
114 .pfn = __phys_to_pfn(S5P_PA_TIMER),
115 .length = SZ_16K,
116 .type = MT_DEVICE,
117 }, {
118 .virtual = (unsigned long)S3C_VA_WATCHDOG,
119 .pfn = __phys_to_pfn(S3C_PA_WDT),
120 .length = SZ_4K,
121 .type = MT_DEVICE,
122 }, {
123 .virtual = (unsigned long)S5P_VA_SROMC,
124 .pfn = __phys_to_pfn(S5P_PA_SROMC),
125 .length = SZ_4K,
126 .type = MT_DEVICE,
127 },
128 };
129
130 /* read cpu identification code */
131
132 void __init s5p_init_io(struct map_desc *mach_desc,
133 int size, void __iomem *cpuid_addr)
134 {
135 /* initialize the io descriptors we need for initialization */
136         iotable_init(s5p_iodesc, ARRAY_SIZE(s5p_iodesc));
137 if (mach_desc)
138                 iotable_init(mach_desc, size);
139
140 /* detect cpu id and rev. */
141         s5p_init_cpu(cpuid_addr);
142
143         s3c_init_cpu(samsung_cpu_id, cpu_ids, ARRAY_SIZE(cpu_ids));
144 }

下面就该看每个io物理地址都是干什么用的，xen都改了哪些，地址空间该怎样映射了。
3.15的kernel里用的是fdt，所以arch\arm\mach-exynos目录下变化非常大，因为描述设备的代码都被fdt配置文件替换了。所以，我想如果在arndale的fdt里能正确的描述LCD，并且kernel对应的驱动也存在，应该能把屏幕驱动起来。

哎，糊里糊涂的点错了，幸亏草稿箱里还有，要不可不想再敲一遍。。。