Hello, I am porting U-Boot to the Allwinner D1 SoC, and I ran into an issue where the board fails to boot if I enable watchdog auto-start.
The call to get_timer() -> get_ticks() panics because no timer is available. And since panic_finish() calls udelay(), this causes infinite recursion of trying and failing to get the timer. The issue is that the RISC-V architectural timer driver is bound in arch_early_init_r, which is only called _after_ the first instance of INIT_FUNC_WATCHDOG_RESET in the initcall list. Below is a boot log where I commented out the calls to get_timer() and time_after_eq() in watchdog_reset() in order to illustrate the problem. I modified the log to add the initcall symbol names for clarity. > U-Boot 2021.10-rc2-00278-ge2be1a426d6-dirty (Jan 01 1970 - 00:00:00 +0000) > > DRAM: 512 MiB > initcall: 000000005ff63916 > initcall: 000000005ff6391a > initcall: 000000004a012a4e (initr_reloc_global_data) > initcall: 000000004a012a88 (initr_barrier) > initcall: 000000004a012a1c (initr_malloc) > Pre-reloc malloc() used 0x720 bytes (1 KB) > initcall: 000000004a01290e (log_init) > initcall: 000000004a012a94 (initr_bootstage) > initcall: 000000004a012a8c (initr_of_live) > initcall: 000000004a012a06 (initr_dm) > Binding device root_driver to driver root_driver > Probing device root_driver with driver root_driver > Binding device osc24M_clk to driver fixed_clock > Binding device soc to driver simple_bus > Binding device pinctrl@2000000 to driver sunxi-pinctrl > Binding device pinctrl@2000000 to driver gpio_sunxi > Binding device PA to driver gpio_sunxi > Binding device PB to driver gpio_sunxi > Binding device PC to driver gpio_sunxi > Binding device PD to driver gpio_sunxi > Binding device PE to driver gpio_sunxi > Binding device PF to driver gpio_sunxi > Binding device PG to driver gpio_sunxi > Binding device i2c0-pb10-pins to driver pinconfig > Binding device i2c2-pb0-pins to driver pinconfig > Binding device mmc0-pins to driver pinconfig > Binding device mmc1-pins to driver pinconfig > Binding device rgmii-pe-pins to driver pinconfig > Binding device spi0-pins to driver pinconfig > Binding device spi1-pd-pins to driver pinconfig > Binding device uart0-pb8-pins to driver pinconfig > Binding device uart1-pg6-pins to driver pinconfig > Binding device uart1-pg8-rts-cts-pins to driver pinconfig > Binding device i2s2-pb-pins to driver pinconfig > Binding device i2s2-pb3-din-pin to driver pinconfig > Binding device i2s2-pb4-dout-pin to driver pinconfig > Binding device ledc-pc0-pin to driver pinconfig > Binding device pwm0-pd16-pin to driver pinconfig > Binding device pwm2-pd18-pin to driver pinconfig > Binding device pwm7-pd22-pin to driver pinconfig > Binding device spdif-pd22-pin to driver pinconfig > Binding device clock-controller@2001000 to driver sun50i_d1_ccu > Binding device reset to driver sunxi_reset > Binding device serial@2500000 to driver ns16550_serial > Binding device serial@2500400 to driver ns16550_serial > Binding device i2c@2502000 to driver i2c_mvtwsi > Binding device i2c@2502800 to driver i2c_mvtwsi > Binding device mmc@4020000 to driver sunxi_mmc > Binding device m...@4020000.blk to driver mmc_blk > Binding device mmc@4021000 to driver sunxi_mmc > Binding device m...@4021000.blk to driver mmc_blk > Binding device usb@4100000 to driver sunxi-musb > Binding device phy@4100400 to driver sun4i_usb_phy > Binding device usb@4101000 to driver ehci_generic > Binding device usb@4101400 to driver ohci_generic > Binding device usb@4200000 to driver ehci_generic > Binding device usb@4200400 to driver ohci_generic > Binding device ethernet@4500000 to driver eth_sun8i_emac > Binding device watchdog@6011000 to driver sunxi_wdt > initcall: 000000004a001914 (board_init) > initcall: 000000004a04d814 (efi_memory_init) > initcall: 000000004a012a9c (initr_binman) > initcall: 000000004a012a90 (initr_dm_devices) Here's where dm_timer_init() would be called if CONFIG_TIMER_EARLY was enabled, but that still doesn't help because the timer is not bound yet. In fact, CONFIG_TIMER_EARLY actually makes the situation worse, because the board hangs if dm_timer_init() fails: initcall sequence 000000005ffdac78 failed at call 000000004a012a06 (err=-19) ### ERROR ### Please RESET the board ### > initcall: 000000004a01c4f4 (stdio_init_tables) > initcall: 000000004a039ff8 (serial_initialize) > Probing device pinctrl@2000000 with driver sunxi-pinctrl > Probing device soc with driver simple_bus > Probing device clock-controller@2001000 with driver sun50i_d1_ccu > Probing device osc24M_clk with driver fixed_clock > Probing device uart0-pb8-pins with driver pinconfig > Probing device serial@2500000 with driver ns16550_serial > Probing device reset with driver sunxi_reset > initcall: 000000004a0129ea (initr_announce) > Now running in RAM - U-Boot at: 5ff51000 > initcall: 000000004a0367ce (initr_watchdog) > Probing device watchdog@6011000 with driver sunxi_wdt > WDT: Started with servicing (16s timeout) > initcall: 000000004a012610 (init_func_watchdog_reset) Here's where the timer needs to be available for watchdog auto-start to work. An unpatched U-Boot would panic here. > initcall: 000000004a012a84 (arch_initr_trap) > initcall: 000000004a012610 (init_func_watchdog_reset) > initcall: 000000004a012610 (init_func_watchdog_reset) > initcall: 000000004a000ed4 (arch_early_init_r) > Binding device cpus to driver cpu_bus > Binding device cpu@0 to driver riscv_cpu > Binding device riscv_timer to driver riscv_timer But here is where the timer device is actually bound. Do you have any suggestions for how best to fix this? Some things I can think of: - Add an option to probe the CPU device early in initr_dm_devices() - Require the board to probe the CPU device from board_init() - Move arch_early_init_r() earlier in the initcall list - Skip restarting the watchdog until a timer is available (but this would not fix CONFIG_TIMER_EARLY) Thanks, Samuel > Probing device cpus with driver cpu_bus > Probing device cpu@0 with driver riscv_cpu > Binding device sbi-sysreset to driver sbi-sysreset > initcall: 000000004a012a98 (power_init_board) > initcall: 000000004a012610 (init_func_watchdog_reset) > initcall: 000000004a0129ca (initr_mmc) > MMC: Probing device mmc0-pins with driver pinconfig > Probing device mmc@4020000 with driver sunxi_mmc > Probing device pinctrl@2000000 with driver gpio_sunxi > Probing device PF with driver gpio_sunxi > Need to init timer! > Probing device riscv_timer with driver riscv_timer > Timer is 000000005df34f80 > Read timer, got 0x17dacfb > Timer is 000000005df34f80 > Read timer, got 0x17f63b8 > Probing device mmc1-pins with driver pinconfig > Probing device mmc@4021000 with driver sunxi_mmc > Timer is 000000005df34f80 > Read timer, got 0x186be7e > Timer is 000000005df34f80 > Read timer, got 0x188752e > mmc@4020000: 0, mmc@4021000: 1 > initcall: 000000004a012970 (relocated to 000000005ff63970) > Loading Environment from nowhere... OK > initcall: 000000004a012610 (relocated to 000000005ff63610) > initcall: 000000004a012912 (relocated to 000000005ff63912) > initcall: 000000004a012610 (relocated to 000000005ff63610) > initcall: 000000004a01c50c (relocated to 000000005ff6d50c) > initcall: 000000004a010938 (relocated to 000000005ff61938) > initcall: 000000004a0188bc (relocated to 000000005ff698bc) > In: serial@2500000 > Out: serial@2500000 > Err: serial@2500000 > initcall: 000000004a012610 (relocated to 000000005ff63610) > initcall: 000000004a0012dc (relocated to 000000005ff522dc) > initcall: 000000004a012950 (relocated to 000000005ff63950) > initcall: 000000004a012610 (relocated to 000000005ff63610) > initcall: 000000004a012934 (relocated to 000000005ff63934) > Net: phy interface8 > Probing device rgmii-pe-pins with driver pinconfig > Probing device ethernet@4500000 with driver eth_sun8i_emac > Timer is 000000005df34f80 > Read timer, got 0x1ae9538 > Timer is 000000005df34f80 > Read timer, got 0x1b04bed > Timer is 000000005df34f80 > Read timer, got 0x1b202af > Timer is 000000005df34f80 > Read timer, got 0x1b3b96e > Timer is 000000005df34f80 > Read timer, got 0x1b5702c > Timer is 000000005df34f80 > Read timer, got 0x1b726ec > > Warning: ethernet@4500000 (eth0) using random MAC address - 62:69:97:68:19:04 > eth0: ethernet@4500000 > initcall: 000000004a01292a (relocated to 000000005ff6392a) > Hit any key to stop autoboot: 0
