Watchdog auto-start and TIMER_EARLY broken in RISC-V U-Boot

[Sean Anderson]

+CC Heinrich

Did you ever try booting with WDT on k210?

On 9/11/21 12:43 PM, Samuel Holland wrote:
> 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 at 2000000 to driver sunxi-pinctrl
>> Binding device pinctrl at 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 at 2001000 to driver sun50i_d1_ccu
>> Binding device reset to driver sunxi_reset
>> Binding device serial at 2500000 to driver ns16550_serial
>> Binding device serial at 2500400 to driver ns16550_serial
>> Binding device i2c at 2502000 to driver i2c_mvtwsi
>> Binding device i2c at 2502800 to driver i2c_mvtwsi
>> Binding device mmc at 4020000 to driver sunxi_mmc
>> Binding device mmc at 4020000.blk to driver mmc_blk
>> Binding device mmc at 4021000 to driver sunxi_mmc
>> Binding device mmc at 4021000.blk to driver mmc_blk
>> Binding device usb at 4100000 to driver sunxi-musb
>> Binding device phy at 4100400 to driver sun4i_usb_phy
>> Binding device usb at 4101000 to driver ehci_generic
>> Binding device usb at 4101400 to driver ohci_generic
>> Binding device usb at 4200000 to driver ehci_generic
>> Binding device usb at 4200400 to driver ohci_generic
>> Binding device ethernet at 4500000 to driver eth_sun8i_emac
>> Binding device watchdog at 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 ###

I'm not sure what's going on here. Why does dm_timer_init get called from initr_dm?
Why does it fail?

--Sean

>> initcall: 000000004a01c4f4 (stdio_init_tables)
>> initcall: 000000004a039ff8 (serial_initialize)
>> Probing device pinctrl at 2000000 with driver sunxi-pinctrl
>> Probing device soc with driver simple_bus
>> Probing device clock-controller at 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 at 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 at 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 at 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 at 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 at 4020000 with driver sunxi_mmc
>> Probing device pinctrl at 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 at 4021000 with driver sunxi_mmc
>> Timer is 000000005df34f80
>> Read timer, got 0x186be7e
>> Timer is 000000005df34f80
>> Read timer, got 0x188752e
>> mmc at 4020000: 0, mmc at 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 at 2500000
>> Out:   serial at 2500000
>> Err:   serial at 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 at 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 at 4500000 (eth0) using random MAC address - 62:69:97:68:19:04
>> eth0: ethernet at 4500000
>> initcall: 000000004a01292a (relocated to 000000005ff6392a)
>> Hit any key to stop autoboot:  0
> 
>