执行reboot后，卡在reboot: Restarting system
/ # reboot
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system reboot
[ 754.486488] reboot: Restarting system
内核重启的入口是：kernel/reboot.c
244 void kernel_restart(char *cmd)
245 {
246 kernel_restart_prepare(cmd);
247 migrate_to_reboot_cpu();
248 syscore_shutdown();
249 if (!cmd)
250 pr_emerg("Restarting system\n");
251 else
252 pr_emerg("Restarting system with command '%s'\n", cmd);
253 kmsg_dump(KMSG_DUMP_RESTART);
254 machine_restart(cmd);
255 }
256 EXPORT_SYMBOL_GPL(kernel_restart);
他会打印Restarting system，然后调用架构定义的machine_restart（），
5.4内核
arch/arm/kernel/reboot.c
136 void machine_restart(char *cmd)
137 {
138 local_irq_disable();
139 smp_send_stop();
140
141 if (arm_pm_restart)
142 arm_pm_restart(reboot_mode, cmd);
143 else
144 do_kernel_restart(cmd);
145
146 /* Give a grace period for failure to restart of 1s */
147 mdelay(1000);
148
149 /* Whoops - the platform was unable to reboot. Tell the user! */
150 printk("Reboot failed -- System halted\n");
151 while (1);
152 }
smp_send_stop（）停止其它cpu，只保持只有一个cpu运行。
如果设置了arm_pm_restart，则使用arm_pm_restart（）实现重启。否则调用do_kernel_restart（）实现重启。
arm_pm_restart是在psci框架设置的
drivers/firmware/psci/psci.c
412 static void __init psci_0_2_set_functions(void)
413 {
414 pr_info("Using standard PSCI v0.2 function IDs\n");
415 psci_ops.get_version = psci_get_version;
416
417 psci_function_id[PSCI_FN_CPU_SUSPEND] =
418 PSCI_FN_NATIVE(0_2, CPU_SUSPEND);
419 psci_ops.cpu_suspend = psci_cpu_suspend;
420
421 psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
422 psci_ops.cpu_off = psci_cpu_off;
423
424 psci_function_id[PSCI_FN_CPU_ON] = PSCI_FN_NATIVE(0_2, CPU_ON);
425 psci_ops.cpu_on = psci_cpu_on;
426
427 psci_function_id[PSCI_FN_MIGRATE] = PSCI_FN_NATIVE(0_2, MIGRATE);
428 psci_ops.migrate = psci_migrate;
429
430 psci_ops.affinity_info = psci_affinity_info;
431
432 psci_ops.migrate_info_type = psci_migrate_info_type;
433
434 arm_pm_restart = psci_sys_reset;
435 printk("================ arm_pm_restart %pS\n", arm_pm_restart);
436
437 pm_power_off = psci_sys_poweroff;
438 }
新的5.15内核arm_pm_restart已经去掉了：使用do_kernel_restart()框架
135 void machine_restart(char *cmd)
136 {
137 local_irq_disable();
138 smp_send_stop();
139
140 do_kernel_restart(cmd);
141
142 /* Give a grace period for failure to restart of 1s */
143 mdelay(1000);
144
145 /* Whoops - the platform was unable to reboot. Tell the user! */
146 printk("Reboot failed -- System halted\n");
147 while (1);
148 }
kernel/reboot.c
216 void do_kernel_restart(char *cmd)
217 {
218 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
219 }
do_kernel_restart()就是执行使用register_restart_handler(struct notifier_block *nb)注册的重启handler。
添加调试信息：
183 int register_restart_handler(struct notifier_block *nb)
184 {
185 printk("==========register restart handler : %pS\n", nb->notifier_call);
186 return atomic_notifier_chain_register(&restart_handler_list, nb);
187 }
[ 0.000000] ==========register restart handler : psci_sys_reset+0x0/0x74
[ 0.992572] ==========register restart handler : watchdog_restart_notifier+0x0/0x28
重启是卡在psci_sys_reset了：
Power State Coordination Interface (PSCI)
这里分析5.15内核：
dts如下：
83 psci: psci {
84 compatible = "arm,psci-1.0";
85 method = "smc";
86 };
初始化在setup_arch的时候调用psci_dt_init
arch/arm/kernel/setup.c setup_arch(char **cmdline_p)
=>psci_dt_init
代码路径：drivers/firmware/psci/psci.c
606 static const struct of_device_id psci_of_match[] __initconst = {
607 { .compatible = "arm,psci", .data = psci_0_1_init},
608 { .compatible = "arm,psci-0.2", .data = psci_0_2_init},
609 { .compatible = "arm,psci-1.0", .data = psci_1_0_init},
610 {},
611 };
612
613 int __init psci_dt_init(void)
614 {
615 struct device_node *np;
616 const struct of_device_id *matched_np;
617 psci_initcall_t init_fn;
618 int ret;
619
620 np = of_find_matching_node_and_match(NULL, psci_of_match, &matched_np);
621
622 if (!np || !of_device_is_available(np))
623 return -ENODEV;
624
625 init_fn = (psci_initcall_t)matched_np->data;
626 ret = init_fn(np);
627
628 of_node_put(np);
629 return ret;
630 }
277 static int get_set_conduit_method(struct device_node *np)
278 {
279 const char *method;
280
281 pr_info("probing for conduit method from DT.\n");
282
283 if (of_property_read_string(np, "method", &method)) {
284 pr_warn("missing \"method\" property\n");
285 return -ENXIO;
286 }
287
288 if (!strcmp("hvc", method)) {
289 set_conduit(SMCCC_CONDUIT_HVC);
290 } else if (!strcmp("smc", method)) {
291 set_conduit(SMCCC_CONDUIT_SMC);
292 } else {
293 pr_warn("invalid \"method\" property: %s\n", method);
294 return -EINVAL;
295 }
296 return 0;
297 }
dts method为smc。所以set_conduit(SMCCC_CONDUIT_SMC)。
261 static void set_conduit(enum arm_smccc_conduit conduit)
262 {
263 switch (conduit) {
264 case SMCCC_CONDUIT_HVC:
265 invoke_psci_fn = __invoke_psci_fn_hvc;
266 break;
267 case SMCCC_CONDUIT_SMC:
268 invoke_psci_fn = __invoke_psci_fn_smc;
269 break;
270 default:
271 WARN(1, "Unexpected PSCI conduit %d\n", conduit);
272 }
273
274 psci_conduit = conduit;
275 }
120 static unsigned long __invoke_psci_fn_smc(unsigned long function_id,
121 unsigned long arg0, unsigned long arg1,
122 unsigned long arg2)
123 {
124 struct arm_smccc_res res;
125
126 arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
127 return res.a0;
128 }
include/linux/arm-smccc.h
361 #define arm_smccc_smc(...) __arm_smccc_smc(__VA_ARGS__, NULL)
arch/arm/kernel/smccc-call.S
52 ENTRY(__arm_smccc_smc)
53 SMCCC SMCCC_SMC
54 ENDPROC(__arm_smccc_smc)
尝试一直qca-smc也无效。应该是pinctrl和watchdog没移植好，trustzone内部应该也是通过watchdog啥的复位的。
2022/5/29 工作：
uboot的reset过程：
arch/arm/lib/reset.c：
26 __weak void reset_misc(void)
27 {
28 }
30 int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
31 {
32 puts ("resetting ...\n");
33
34 udelay (50000); /* wait 50 ms */
35
36 disable_interrupts();
37
38 reset_misc();
39 reset_cpu(0);
40
41 /*NOTREACHED*/
42 return 0;
43 }
进入到
board/qca/arm/ipq5018/ipq5018.c
754 void reset_cpu(unsigned long a)
755 {
756 reset_crashdump();
757 if (is_scm_armv8())
758 {
759 printf("=======psci sys reset3\n");
760 psci_sys_reset();
761 }
762 else {
763 printf("=======qti reset\n");
764 qti_scm_pshold();
765 }
766 while(1);
767 }
is_scm_armv8() 为真。尝试注释掉reset_crashdump()后不能复位。
726 void reset_crashdump(void)
727 {
728 unsigned int ret = 0;
729 qca_scm_sdi();
730 ret = qca_scm_dload(CLEAR_MAGIC);
731 if (ret)
732 printf ("Error in reseting the Magic cookie\n");
733 return;
734 }
尝试注释掉qca_scm_sdi(); 不能复位，尝试注释掉qca_scm_dload(CLEAR_MAGIC); 可以复位。
因为问题出现在 qca_scm_sdi。
arch/arm/cpu/armv7/qca/common/scm.c
767
768 static int qca_scm_sdi_v8(void)
769 {
770 struct qca_scm_desc desc = {0};
771 int ret;
772
773 desc.args[0] = 1ul; /* Disable wdog debug */
774 desc.args[1] = 0ul; /* SDI Enable */
775 desc.arginfo = QCA_SCM_ARGS(2, SCM_VAL, SCM_VAL);
776 ret = scm_call_64(SCM_SVC_BOOT,
777 SCM_CMD_TZ_CONFIG_HW_FOR_RAM_DUMP_ID, &desc);
778
779 if (ret)
780 return ret;
781
782 return le32_to_cpu(desc.ret[0]);
783 }
785 int qca_scm_sdi(void)
786 {
787 int ret;
788 unsigned int clear_info[] = {
789 1 /* Disable wdog debug */, 0 /* SDI enable*/, };
790
791 if (is_scm_armv8())
792 return qca_scm_sdi_v8();
793
794 ret = scm_call(SCM_SVC_BOOT, SCM_CMD_TZ_CONFIG_HW_FOR_RAM_DUMP_ID, &clear_info,
795 sizeof(clear_info), NULL, 0);
796
797 return ret;
798 }
查找4.4内核相关代码，发现：
./drivers/firmware/qca_scm_restart_reason.c:100: qcom_scm_sdi(QCOM_SCM_SVC_BOOT, SCM_CMD_TZ_CONFIG_HW_FOR_RAM_DUMP_ID);
而新版内核，没有qca_scm_restart_reason.c了。因此定位出原因了。在老的qseecom需要调用SCM_CMD_TZ_CONFIG_HW_FOR_RAM_DUMP_ID。
参考
https://developer.arm.com/Architectures/Power%20State%20Coordination%20Interface
https://www.cnblogs.com/loyenwang/p/11370557.html
https://discuss.96boards.org/t/reset-reboot-behavior/5293
https://github.com/ARM-software/arm-trusted-firmware
有讲到PSCI和SCM