setup_arch(4) - PSCI partial

看完local_async_enable, 繼續 trace setup_arch()囉
[cpu_uninstall_idmap]

         /*
          * TTBR0 is only used for the identity mapping at this stage. Make it
          * point to zero page to avoid speculatively fetching new entries.
          */
         cpu_uninstall_idmap();

看到TTBR0了, 先來看看這個register在幹嘛? Programmers Guide的定義如下

TTBR0_ELn (Translation Table Base Register 0)

Holds the base address of translation table 0, and information

about the memory it occupies. This is one of the translation

tables for the stage 1 translation of memory accesses at ELn.

TTBR0儲存PGD的address, 因此現階段一律將TTBR0指到zero page
detail以後有空再trace

[keep going]

         xen_early_init();
         efi_init();
         arm64_memblock_init();

xen_early_init():

處理hypervisor的device tree (more see Documentation/devicetree/bindings/arm/xen.txt for the 258 * documentation of the Xen Device Tree format.)

efi_init():

跟UEFI related 的operations --> skip

arm64_memblock_init():

在系統初始化階段, Linux 的memory 機制尚未啟動(buddy), 因此系統init初期是使用memblock 機制來分配physical memory 給大家使用

more can see reference as follows

(1) http://www.maxwellxxx.com/linuxmemblock

(2) http://blog.jobbole.com/88452/

(3) http://lib.csdn.net/article/linux/45665

         paging_init();
 
         acpi_table_upgrade();
 
         /* Parse the ACPI tables for possible boot-time configuration */
         acpi_boot_table_init();
 
         if (acpi_disabled)
                 unflatten_device_tree();
 
         bootmem_init();

paging_init():

set up page tables (initialize paging mechanism)

acpi_table_upgrade():

acpi_boot_table_init():

skip

bootmem_init():

initialize memory management.

more can see reference as follows

(1) http://www.voidcn.com/blog/gatieme/article/p-6183366.html

         kasan_init();
 
         request_standard_resources();
 
         early_ioremap_reset();
 
         if (acpi_disabled)
                 psci_dt_init();
         else
                 psci_acpi_init();
 
         cpu_read_bootcpu_ops();
         smp_init_cpus();
         smp_build_mpidr_hash();
 
 #ifdef CONFIG_VT
 #if defined(CONFIG_VGA_CONSOLE)
         conswitchp = &vga_con;
 #elif defined(CONFIG_DUMMY_CONSOLE)
         conswitchp = &dummy_con;
 #endif
 #endif
         if (boot_args[1] || boot_args[2] || boot_args[3]) {
                 pr_err("WARNING: x1-x3 nonzero in violation of boot protocol:\n"
                         "\tx1: %016llx\n\tx2: %016llx\n\tx3: %016llx\n"
                         "This indicates a broken bootloader or old kernel\n",
                         boot_args[1], boot_args[2], boot_args[3]);
         }

kasan_init():

kernel address sanitizer

是一個可以dynamic memory error detector

more can see the reference as follows 

(1) http://www.ibm.com/developerworks/cn/linux/1608_tengr_kasan/index.html

(2) http://lxr.free-electrons.com/source/Documentation/kasan.txt

request_standard_resource():

每一個cpu上掛的device 會用一個struct resource 記錄這個device需要使用的physical address(iomem)的info (eg. 起始位置)

more can see the reference as follows

(1) http://blog.csdn.net/boarmy/article/details/8652763

early_ioremap_reset():

set after_paging_init = 1

psci_dt_init():

acpi_disabled =1 被define在 arch/arm64/kernel/acpi.c, line 38

grep .config 也沒有發現CONFIG_PSCI

因此會走psci_dt_init()

 static const struct of_device_id psci_of_match[] __initconst = {
         { .compatible = "arm,psci",     .data = psci_0_1_init},
         { .compatible = "arm,psci-0.2", .data = psci_0_2_init},
         { .compatible = "arm,psci-1.0", .data = psci_0_2_init},
         {},
 };

 int __init psci_dt_init(void)
 {
         struct device_node *np;
         const struct of_device_id *matched_np;
         psci_initcall_t init_fn;
 
         np = of_find_matching_node_and_match(NULL, psci_of_match, &matched_np);
 
         if (!np)
                 return -ENODEV;
 
         init_fn = (psci_initcall_t)matched_np->data;
         return init_fn(np);
 }

of_find_matching_node_and_match() 會到device tree中search 有無與 psci_of_match[] 中定義的element 一樣的node (根據compatible), 若有找到, 將 matched_np 指向psci_of_match[]中的element

for example, we got compatible="arm,psci-0.2" in our device tree, 因此match_np指向psci_of_match[1], 代表目前使用的是psci 0.2 版

接著將matched_np->data 轉成function pointer

然後執行psci_0_2_init, 同時帶入參數np

 typedef int (*psci_initcall_t)(const struct device_node *);
 
 /*
  * PSCI init function for PSCI versions >=0.2
  *
  * Probe based on PSCI PSCI_VERSION function
  */
 static int __init psci_0_2_init(struct device_node *np)
 {
         int err;
 
         err = get_set_conduit_method(np);
 
         if (err)
                 goto out_put_node;
         /*
          * Starting with v0.2, the PSCI specification introduced a call
          * (PSCI_VERSION) that allows probing the firmware version, so
          * that PSCI function IDs and version specific initialization
          * can be carried out according to the specific version reported
          * by firmware
          */
         err = psci_probe();
 
 out_put_node:
         of_node_put(np);
         return err;
 }

device tree will define psci node like this
psci {
    compatible = "arm, psci-0.2";
    method = "smc";
}
(http://lxr.free-electrons.com/source/arch/arm64/boot/dts/mediatek/mt6795.dtsi)

get_set_conduit_method() 會到device tree找這個node
用of_property_read_string(np, "method", &method)找 method

由node可知, psci在這邊是用smc的方式進入ATF, 因此會將invoke_psci_fn設定為 __invoke_psci_fn_smc

部分的get_set_conduit_method() code如下

if (!strcmp("hvc", method)) {
                 invoke_psci_fn = __invoke_psci_fn_hvc;
         } else if (!strcmp("smc", method)) {
                 invoke_psci_fn = __invoke_psci_fn_smc;

invoke_psci_fn是一個function pointer定義如下

  typedef unsigned long (psci_fn)(unsigned long, unsigned long,
                                  unsigned long, unsigned long);
  static psci_fn *invoke_psci_fn;

回到psci_0_2_init()

接著執行psci_probe()

 static int __init psci_probe(void)
 {
         u32 ver = psci_get_version();
 
         pr_info("PSCIv%d.%d detected in firmware.\n",
                         PSCI_VERSION_MAJOR(ver),
                         PSCI_VERSION_MINOR(ver));
 
         if (PSCI_VERSION_MAJOR(ver) == 0 && PSCI_VERSION_MINOR(ver) < 2) {
                 pr_err("Conflicting PSCI version detected.\n");
                 return -EINVAL;
         }
 
         psci_0_2_set_functions();
 
         psci_init_migrate();
 
         if (PSCI_VERSION_MAJOR(ver) >= 1) {
                 psci_init_cpu_suspend();
                 psci_init_system_suspend();
         }
 
         return 0;
 }

(1) psci_get_version()

call invoke_psci_fn (也就是__invoke_psci_fn_smc()) get firmware version

(2) psci_0_2_set_functions()

 static void __init psci_0_2_set_functions(void)
 {
         pr_info("Using standard PSCI v0.2 function IDs\n");
         psci_function_id[PSCI_FN_CPU_SUSPEND] =
                                         PSCI_FN_NATIVE(0_2, CPU_SUSPEND);
         psci_ops.cpu_suspend = psci_cpu_suspend;
 
         psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
         psci_ops.cpu_off = psci_cpu_off;
 
         psci_function_id[PSCI_FN_CPU_ON] = PSCI_FN_NATIVE(0_2, CPU_ON);
         psci_ops.cpu_on = psci_cpu_on;
 
         psci_function_id[PSCI_FN_MIGRATE] = PSCI_FN_NATIVE(0_2, MIGRATE);
         psci_ops.migrate = psci_migrate;
 
         psci_ops.affinity_info = psci_affinity_info;
 
         psci_ops.migrate_info_type = psci_migrate_info_type;
 
         arm_pm_restart = psci_sys_reset;
 
         pm_power_off = psci_sys_poweroff;
 }

首先psci.c裡面有define

enum psci_function {
PSCI_FN_CPU_SUSPEND,
PSCI_FN_CPU_ON,
PSCI_FN_CPU_OFF,
PSCI_FN_MIGRATE,
PSCI_FN_MAX,
};
static u32 psci_function_id[PSCI_FN_MAX];

psci有四種function, 這些function各有id define在上面的enum裡
另外還有 PSCI_FN_NATIVE 這個macro, 

 /*
   * While a 64-bit OS can make calls with SMC32 calling conventions, for some
   * calls it is necessary to use SMC64 to pass or return 64-bit values.
   * For such calls PSCI_FN_NATIVE(version, name) will choose the appropriate
   * (native-width) function ID.
   */
  #ifdef CONFIG_64BIT
  #define PSCI_FN_NATIVE(version, name)   PSCI_##version##_FN64_##name
  #else
  #define PSCI_FN_NATIVE(version, name)   PSCI_##version##_FN_##name
  #endif

我們有define CONFIG_64BIT
因此macro 炸開會變成 PSCI_0_2_FN64_[NAME]

另外還有一個重要的params
struct psci_operations psci_ops;

這是一個psci_operations, struct定義如下

 struct psci_operations {
          int (*cpu_suspend)(u32 state, unsigned long entry_point);
          int (*cpu_off)(u32 state);
          int (*cpu_on)(unsigned long cpuid, unsigned long entry_point);
          int (*migrate)(unsigned long cpuid);
          int (*affinity_info)(unsigned long target_affinity,
                          unsigned long lowest_affinity_level);
          int (*migrate_info_type)(void);
  };

回到psci_0_2_set_functions()會發現這個function一開始會設定大家的suspend/on/off/migrate 的function id, 以及掛上callback functions
深入進去看

psci_function_id[PSCI_FN_CPU_SUSPEND] =PSCI_0_2_CPU_SUSPEND

psci_ops.cpu_suspend = psci_cpu_suspend;

(WHERE defines) PSCI_0_2_CPU_SUSPEND ??

psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF

psci_ops.cpu_off = psci_cpu_off;

psci_function_id[PSCI_FN_CPU_ON] = PSCI_FN_0_2,_CPU_ON

psci_ops.cpu_on = psci_cpu_on;

psci_function_id[PSCI_FN_MIGRATE] = PSCI_FN_0_2_MIGRATE

psci_ops.migrate = psci_migrate;

psci_ops.affinity_info = psci_affinity_info;

psci_ops.migrate_info_type = psci_migrate_info_type;

關於function id 定義在http://lxr.free-electrons.com/source/include/uapi/linux/psci.h#L34

 /* PSCI v0.2 interface */
  #define PSCI_0_2_FN_BASE                        0x84000000
  #define PSCI_0_2_FN(n)                          (PSCI_0_2_FN_BASE + (n))
  #define PSCI_0_2_64BIT                          0x40000000
  #define PSCI_0_2_FN64_BASE                      \
                                          (PSCI_0_2_FN_BASE + PSCI_0_2_64BIT)
  #define PSCI_0_2_FN64(n)                        (PSCI_0_2_FN64_BASE + (n))
  
  #define PSCI_0_2_FN_PSCI_VERSION                PSCI_0_2_FN(0)
  #define PSCI_0_2_FN_CPU_SUSPEND                 PSCI_0_2_FN(1)
  #define PSCI_0_2_FN_CPU_OFF                     PSCI_0_2_FN(2)
  #define PSCI_0_2_FN_CPU_ON                      PSCI_0_2_FN(3)
  #define PSCI_0_2_FN_AFFINITY_INFO               PSCI_0_2_FN(4)
  #define PSCI_0_2_FN_MIGRATE                     PSCI_0_2_FN(5)
  #define PSCI_0_2_FN_MIGRATE_INFO_TYPE           PSCI_0_2_FN(6)
  #define PSCI_0_2_FN_MIGRATE_INFO_UP_CPU         PSCI_0_2_FN(7)
  #define PSCI_0_2_FN_SYSTEM_OFF                  PSCI_0_2_FN(8)
  #define PSCI_0_2_FN_SYSTEM_RESET                PSCI_0_2_FN(9)
  
  #define PSCI_0_2_FN64_CPU_SUSPEND               PSCI_0_2_FN64(1)
  #define PSCI_0_2_FN64_CPU_ON                    PSCI_0_2_FN64(3)
  #define PSCI_0_2_FN64_AFFINITY_INFO             PSCI_0_2_FN64(4)
  #define PSCI_0_2_FN64_MIGRATE                   PSCI_0_2_FN64(5)
  #define PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU       PSCI_0_2_FN64(7)
  
  #define PSCI_1_0_FN_PSCI_FEATURES               PSCI_0_2_FN(10)
  #define PSCI_1_0_FN_SYSTEM_SUSPEND              PSCI_0_2_FN(14)
  
  #define PSCI_1_0_FN64_SYSTEM_SUSPEND            PSCI_0_2_FN64(14)

所有的function id 都是psci base + idx
我看的是64bit的case
因此 psci base = PSCI_0_2_FN64_BASE = 0xC4000000
psci version id = base + 0
cpu_suspend = base + 1
依此類推

另外還有兩個function pointers: arm_pm_restart, pm_power_off

分別hook 上psci_sys_reset, psci_sys_poweroff

指定reset & poweroff時要做什麼事

arm_pm_restart = psci_sys_reset;

pm_power_off = psci_sys_poweroff;

(3) psci_init_migrate()

skip

(4) psci_init_cpu_suspend()

 static void __init psci_init_cpu_suspend(void)
 {
         int feature = psci_features(psci_function_id[PSCI_FN_CPU_SUSPEND]);
 
         if (feature != PSCI_RET_NOT_SUPPORTED)
                 psci_cpu_suspend_feature = feature;
 }

主要是將 cpu suspend 的function id 帶入 psci features function, 檢查cpu suspend 的function handler 是否存在
而要看cpu_suspend是否存在, 要看psci_features return的64bit value
return value 的format 如下

if Func ID 是 0x84000001(SMC32)/0xC4000001 (SMC64) for CPU_SUSPEND
Bits[31:2] : 若存在, must be 0
Bits[1:1]: 0 if the implementation uses original format for the power_state parameter
                1 if the implementation uses the new extended StateID format for the power_state param
Bits[0:0]: 0 if not support os initiated mode
                 1 if support os initiated mode
else
its[31:0] : 若存在, must be 0

return value 會跟 PSCI_RET_NOT_SUPPORTET(-1)比對, 若不為-1代表存在就將 feature assign 給 psci_cpu_suspend 這個variable

進一步看一下psci_features (第一個參數是psci_feature本身的function id, 第二個參數是欲查詢的function id

 static int __init psci_features(u32 psci_func_id)
 {
         return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
                               psci_func_id, 0, 0);
 }

psci_features 裡面其實是個smc call, invoke_psci_fn相當於__invoke_psci_fn_smc

如下, __invoke_psci_fn_smc裡面call arm_smccc_smc才會真正做一次smc call 到EL3, 第一個參數為function id, 後面有三個arg 可以將info帶入到smc call

 static unsigned long __invoke_psci_fn_smc(unsigned long function_id,
                         unsigned long arg0, unsigned long arg1,
                         unsigned long arg2)
 {
         struct arm_smccc_res res;
 
         arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
         return res.a0;
 }

arm_smccc_smc() 定義在http://lxr.free-electrons.com/source/include/linux/arm-smccc.h#L84
底層的EL3 應該是assembly code, 因此這裡加上gcc compile conigs asmlinkage
並且將要傳遞的參數存入register 0-7

 /**
   * arm_smccc_smc() - make SMC calls
   * @a0-a7: arguments passed in registers 0 to 7
   * @res: result values from registers 0 to 3
   *
   * This function is used to make SMC calls following SMC Calling Convention.
   * The content of the supplied param are copied to registers 0 to 7 prior
   * to the SMC instruction. The return values are updated with the content
   * from register 0 to 3 on return from the SMC instruction.
   */
  asmlinkage void arm_smccc_smc(unsigned long a0, unsigned long a1,
                          unsigned long a2, unsigned long a3, unsigned long a4,
                          unsigned long a5, unsigned long a6, unsigned long a7,
                          struct arm_smccc_res *res);

另外smc call 的results會被存在 res 裡

  /**
   * struct arm_smccc_res - Result from SMC/HVC call
   * @a0-a3 result values from registers 0 to 3
   */
  struct arm_smccc_res {
          unsigned long a0;
          unsigned long a1;
          unsigned long a2;
          unsigned long a3;
  };

(5) psci_init_system_suspend()
    跟cpu suspend init做一樣的動作

到這裡psci_probe 結束
回到psci_0_2_init
再回到 psci_dt_init結束
最後終於回到setup_arch....