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 mmc@4020000.blk to driver mmc_blk Binding device mmc@4021000 to driver sunxi_mmc Binding device mmc@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