linux的kernel是怎样工作的（TI_DM36X_ARM系统）(3)

start_kernel调用setup_arch()函数作为执行的第一步，在其中完成特定于体系结构的设置

 

void __init
setup_arch(char **cmdline_p)
{
        extern char _end[];

        struct alpha_machine_vector *vec = NULL;
        struct percpu_struct *cpu;
        char *type_name, *var_name, *p;
        void *kernel_end = _end; /* end of kernel */
        char *args = command_line;

        hwrpb = (struct hwrpb_struct*) __va(INIT_HWRPB->phys_addr);
        boot_cpuid = hard_smp_processor_id();
        
        /*         
         * Pre-process the system type to make sure it will be valid.
         *
         * This may restore real CABRIO and EB66+ family names, ie
         * EB64+ and EB66.
         *
         * Oh, and "white box" AS800 (aka DIGITAL Server 3000 series)
         * and AS1200 (DIGITAL Server 5000 series) have the type as
         * the negative of the real one.
         */
       if ((long)hwrpb->sys_type < 0) {
                hwrpb->sys_type = -((long)hwrpb->sys_type);
                hwrpb_update_checksum(hwrpb);
        }

        /* Register a call for panic conditions. */
        atomic_notifier_chain_register(&panic_notifier_list,
                        &alpha_panic_block);

#ifdef CONFIG_ALPHA_GENERIC
        /* Assume that we've booted from SRM if we haven't booted from MILO.
           Detect the later by looking for "MILO" in the system serial nr.  */
        alpha_using_srm = strncmp((const char *)hwrpb->ssn, "MILO", 4) != 0;
#endif

        /* If we are using SRM, we want to allow callbacks
           as early as possible, so do this NOW, and then
           they should work immediately thereafter.
        */
        kernel_end = callback_init(kernel_end);

        /* 
         * Locate the command line.
         */
        /* Hack for Jensen... since we're restricted to 8 or 16 chars for
           boot flags depending on the boot mode, we need some shorthand.
           This should do for installation.  */
        if (strcmp(COMMAND_LINE, "INSTALL") == 0) {
                strlcpy(command_line, "root=/dev/fd0 load_ramdisk=1", sizeof command_line);
        } else {
                strlcpy(command_line, COMMAND_LINE, sizeof command_line);
        }
        strcpy(boot_command_line, command_line);
        *cmdline_p = command_line;
       /* 
         * Process command-line arguments.
         */
        while ((p = strsep(&args, " \t")) != NULL) {
                if (!*p) continue;
                if (strncmp(p, "alpha_mv=", 9) == 0) {
                        vec = get_sysvec_byname(p+9);
                        continue;
                }
                if (strncmp(p, "cycle=", 6) == 0) {
                        est_cycle_freq = simple_strtol(p+6, NULL, 0);
                        continue;
                }
                if (strncmp(p, "mem=", 4) == 0) {
                        mem_size_limit = get_mem_size_limit(p+4);
                        continue;
                }
                if (strncmp(p, "srmcons", 7) == 0) {
                        srmcons_output |= 1;
                        continue;
                }
                if (strncmp(p, "console=srm", 11) == 0) {
                        srmcons_output |= 2;
                        continue;
                }
                if (strncmp(p, "gartsize=", 9) == 0) {
                        alpha_agpgart_size =
                                get_mem_size_limit(p+9) << PAGE_SHIFT;
                        continue;
                }
#ifdef CONFIG_VERBOSE_MCHECK
                if (strncmp(p, "verbose_mcheck=", 15) == 0) {
                        alpha_verbose_mcheck = simple_strtol(p+15, NULL, 0);
                        continue;
                }
#endif
        }
      /* Replace the command line, now that we've killed it with strsep.  */
        strcpy(command_line, boot_command_line);

        /* If we want SRM console printk echoing early, do it now. */
        if (alpha_using_srm && srmcons_output) {
                register_srm_console();

                /*
                 * If "console=srm" was specified, clear the srmcons_output
                 * flag now so that time.c won't unregister_srm_console
                 */
                if (srmcons_output & 2)
                        srmcons_output = 0;
        }

#ifdef CONFIG_MAGIC_SYSRQ
        /* If we're using SRM, make sysrq-b halt back to the prom,
           not auto-reboot.  */
        if (alpha_using_srm) {
                struct sysrq_key_op *op = __sysrq_get_key_op('b');
                op->handler = (void *) machine_halt;
        }
#endif

        /*
         * Identify and reconfigure for the current system.
         */
        cpu = (struct percpu_struct*)((char*)hwrpb + hwrpb->processor_offset);

        get_sysnames(hwrpb->sys_type, hwrpb->sys_variation,
                     cpu->type, &type_name, &var_name);
        if (*var_name == '0')
                var_name = "";

        if (!vec) {
                vec = get_sysvec(hwrpb->sys_type, hwrpb->sys_variation,
                                 cpu->type);
        }
     if (!vec) {
                panic("Unsupported system type: %s%s%s (%ld %ld)\n",
                      type_name, (*var_name ? " variation " : ""), var_name,
                      hwrpb->sys_type, hwrpb->sys_variation);
        }
        if (vec != &alpha_mv) {
                alpha_mv = *vec;
        }

        printk("Booting "
#ifdef CONFIG_ALPHA_GENERIC
               "GENERIC "
#endif
               "on %s%s%s using machine vector %s from %s\n",
               type_name, (*var_name ? " variation " : ""),
               var_name, alpha_mv.vector_name,
               (alpha_using_srm ? "SRM" : "MILO"));

        printk("Major Options: "
#ifdef CONFIG_SMP
               "SMP "
#endif
#ifdef CONFIG_ALPHA_EV56
               "EV56 "
#endif
#ifdef CONFIG_ALPHA_EV67
               "EV67 "
#endif
#ifdef CONFIG_ALPHA_LEGACY_START_ADDRESS
               "LEGACY_START "
#endif
#ifdef CONFIG_VERBOSE_MCHECK
               "VERBOSE_MCHECK "
#endif

#ifdef CONFIG_DISCONTIGMEM
               "DISCONTIGMEM "
#ifdef CONFIG_NUMA
               "NUMA "
#endif
#endif
#ifdef CONFIG_DEBUG_SPINLOCK
               "DEBUG_SPINLOCK "
#endif
#ifdef CONFIG_MAGIC_SYSRQ
               "MAGIC_SYSRQ "
#endif
               "\n");

        printk("Command line: %s\n", command_line);

        /* 
         * Sync up the HAE.
         * Save the SRM's current value for restoration.
         */
        srm_hae = *alpha_mv.hae_register;
        __set_hae(alpha_mv.hae_cache);

        /* Reset enable correctable error reports.  */
        wrmces(0x7);

        /* Find our memory.  */
        setup_memory(kernel_end);

        /* First guess at cpu cache sizes.  Do this before init_arch.  */
        determine_cpu_caches(cpu->type);

        /* Initialize the machine.  Usually has to do with setting up
           DMA windows and the like.  */
        if (alpha_mv.init_arch)
                alpha_mv.init_arch();
      /* Reserve standard resources.  */
        reserve_std_resources();

        /* 
         * Give us a default console.  TGA users will see nothing until
         * chr_dev_init is called, rather late in the boot sequence.
         */

#ifdef CONFIG_VT
#if defined(CONFIG_VGA_CONSOLE)
        conswitchp = &vga_con;
#elif defined(CONFIG_DUMMY_CONSOLE)
        conswitchp = &dummy_con;
#endif
#endif

        /* Default root filesystem to sda2.  */
        ROOT_DEV = Root_SDA2;

#ifdef CONFIG_EISA
        /* FIXME:  only set this when we actually have EISA in this box? */
        EISA_bus = 1;
#endif

        /*
         * Check ASN in HWRPB for validity, report if bad.
         * FIXME: how was this failing?  Should we trust it instead,
         * and copy the value into alpha_mv.max_asn?
         */

        if (hwrpb->max_asn != MAX_ASN) {
                printk("Max ASN from HWRPB is bad (0x%lx)\n", hwrpb->max_asn);
        }

        /*
         * Identify the flock of penguins.
         */
#ifdef CONFIG_SMP
        setup_smp();
#endif
        paging_init();
}

先存档，分析见后续更新