[U-Boot] rockchip: add support for backing to bootrom download mode
Andy Yan
andy.yan at rock-chips.com
Wed Sep 13 08:36:57 UTC 2017
Hi Philipp:
On 2017年09月13日 16:01, Dr. Philipp Tomsich wrote:
>
>> On 13 Sep 2017, at 03:23, Andy Yan <andy.yan at rock-chips.com
>> <mailto:andy.yan at rock-chips.com>> wrote:
>>
>> Hi Philipp:
>>
>>
>> On 2017年09月13日 03:30, Philipp Tomsich wrote:
>>>
>>>
>>> On Mon, 11 Sep 2017, Andy Yan wrote:
>>>
>>>> Rockchip bootrom will enter download mode if it returns from
>>>> spl/tpl with a none-zero value and couldn't find a valid image
>>>> in the backup partition.
>>>> This patch provide a method to instruct the system to back to
>>>> bootrom download mode by checking the BROM_DOWNLOAD_FLAG register.
>>>> As the bootrom download function relys on some modules such as
>>>> interrupts, so we need to back to bootrom as early as possbile
>>>> before the tpl/tps code override the interrupt settings.
>>>
>>> I was not aware that the TPL/SPL overrides interrupt settings. What
>>> exactly does this comment refer to?
>>
>> For armv7, the VBAR and V in SCTLR(which should be 1 for rk3288
>> and zero for other arm32 platforms)
>> are override in arch/cpu/armv7/start.S
>> For armv8, I also find the VBAR related settings, but I didn't
>> test it.
>> I am not sure is there any other settings in the TPL/SPL startup
>> code that will override the default setting in
>> bootrom(maybe mmu, cache and other feathers added to the startup code
>> in the future, this is out of control),
>> but the VBAR and V are indeed override on arm32 platforms. So I think
>> back to bootrom download mode if the
>> flag is set before anything changed is a efficient way.
>
> Should we save these flags as part of the "save_boot_params +
> back_to_bootrom_s” processing?
>
>>>
>>>>
>>>> Signed-off-by: Andy Yan <andy.yan at rock-chips.com
>>>> <mailto:andy.yan at rock-chips.com>>
>>>> Reviewed-by: Kever Yang <kever.yang at rock-chips.com
>>>> <mailto:kever.yang at rock-chips.com>>
>>>> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com
>>>> <mailto:philipp.tomsich at theobroma-systems.com>>
>>>> ---
>>>>
>>>> arch/arm/include/asm/arch-rockchip/bootrom.h | 2 +-
>>>> arch/arm/mach-rockchip/Kconfig | 13 +++++++
>>>> arch/arm/mach-rockchip/bootrom.c | 2 +-
>>>> arch/arm/mach-rockchip/save_boot_param.S | 57
>>>> +++++++++++++++++++++++-----
>>>> 4 files changed, 63 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/arch/arm/include/asm/arch-rockchip/bootrom.h
>>>> b/arch/arm/include/asm/arch-rockchip/bootrom.h
>>>> index 92eb878..6ae3e94 100644
>>>> --- a/arch/arm/include/asm/arch-rockchip/bootrom.h
>>>> +++ b/arch/arm/include/asm/arch-rockchip/bootrom.h
>>>> @@ -22,6 +22,6 @@ void back_to_bootrom(void);
>>>> /**
>>>> * Assembler component for the above (do not call this directly)
>>>> */
>>>> -void _back_to_bootrom_s(void);
>>>> +void _back_to_bootrom_s(int mode);
>>>
>>> Please add documentation for externally visible functions.
>> Okay.
>>>
>>>>
>>>> #endif
>>>> diff --git a/arch/arm/mach-rockchip/Kconfig
>>>> b/arch/arm/mach-rockchip/Kconfig
>>>> index d9b25d5..3ab0c30 100644
>>>> --- a/arch/arm/mach-rockchip/Kconfig
>>>> +++ b/arch/arm/mach-rockchip/Kconfig
>>>> @@ -113,6 +113,7 @@ config ROCKCHIP_RK3399
>>>> select SPL_SERIAL_SUPPORT
>>>> select SPL_DRIVERS_MISC_SUPPORT
>>>> select ENABLE_ARM_SOC_BOOT0_HOOK
>>>> + select ROCKCHIP_BROM_HELPER
>>>> select DEBUG_UART_BOARD_INIT
>>>> help
>>>> The Rockchip RK3399 is a ARM-based SoC with a dual-core Cortex-A72
>>>> @@ -149,6 +150,18 @@ config TPL_ROCKCHIP_BACK_TO_BROM
>>>> SPL will return to the boot rom, which will then load the
>>>> U-Boot
>>>> binary to keep going on.
>>>>
>>>> +config ROCKCHIP_BACK_TO_BROM_DOWNLOAD_REG
>>>> + hex "Bootrom download mode flag register address"
>>>> + default 0x200081c8 if ROCKCHIP_RK3036
>>>> + default 0xff730094 if ROCKCHIP_RK3288
>>>> + default 0xff738200 if ROCKCHIP_RK3368
>>>> + default 0xff320300 if ROCKCHIP_RK3399
>>>> + default 0x10300580 if ROCKCHIP_RV1108
>>>> + default 0x00
>>>
>>> If this is not user-configurable (i.e. if it is a per-chip
>>> constant), we should define this in a header file. I would suggest
>>> to do the detection/mapping either in
>>> include/asm/arch-rockchip/bootrom.h or in a cpu-specific header that
>>> gets included from there.
>>
>> Actually this is user-configuarable, we just chose a register that
>> not be used by the system to pass the boot mode flag.
>> And we also have boards that don't want to enable this function, so
>> they can set the register address to 0. then we will ship
>> the mode check .
>
> Understood.
>
>>>
>>>> + help
>>>> + The Soc will return to bootrom download mode if this
>>>> register set
>>>> + to BOOTROM_DOWNLOAD_FLAG.
>>>
>>> Documenting here what BOOTROM_DOWNLOAD_FLAG is or where it can be
>>> found would be very helpful to anyone coming across this in the future.
>>
>> okay
>>>
>>>> +
>>>> config ROCKCHIP_SPL_RESERVE_IRAM
>>>> hex "Size of IRAM reserved in SPL"
>>>> default 0x4000
>>>> diff --git a/arch/arm/mach-rockchip/bootrom.c
>>>> b/arch/arm/mach-rockchip/bootrom.c
>>>> index 8380e4e..6f0d583 100644
>>>> --- a/arch/arm/mach-rockchip/bootrom.c
>>>> +++ b/arch/arm/mach-rockchip/bootrom.c
>>>> @@ -12,5 +12,5 @@ void back_to_bootrom(void)
>>>> #if CONFIG_IS_ENABLED(LIBCOMMON_SUPPORT)
>>>> puts("Returning to boot ROM...\n");
>>>> #endif
>>>> - _back_to_bootrom_s();
>>>> + _back_to_bootrom_s(0);
>>>> }
>>>> diff --git a/arch/arm/mach-rockchip/save_boot_param.S
>>>> b/arch/arm/mach-rockchip/save_boot_param.S
>>>> index 50fce20..f1bed0b 100644
>>>> --- a/arch/arm/mach-rockchip/save_boot_param.S
>>>> +++ b/arch/arm/mach-rockchip/save_boot_param.S
>>>> @@ -7,11 +7,25 @@
>>>>
>>>> #include <linux/linkage.h>
>>>>
>>>> +#define BACK_TO_BROM_DOWNLOAD_FLAG 0xEF08A53C
>>>
>>> This looks like it should be defined in bootrom.h
>>
>> It has been move to boot-mode.h in new version.
>>>
>>>> +
>>>> #if defined(CONFIG_ARM64)
>>>> .globl SAVE_SP_ADDR
>>>> SAVE_SP_ADDR:
>>>> .quad 0
>>>>
>>>> +ENTRY(check_back_to_brom_dnl_flag)
>>>> + ldr x8, =CONFIG_ROCKCHIP_BACK_TO_BROM_DOWNLOAD_REG
>>>> + ldr x9, [x8]
>>>> + ldr x0, =BACK_TO_BROM_DOWNLOAD_FLAG
>>>> + cmp x9, x0
>>>> + b.ne save_boot_params_ret
>>>> + mov x9, xzr
>>>> + str x9, [x8] /* clear flag */
>>>> + mov x0, #1 /* indicate the bootrom to enter
>>>> download mode */
>>>> + b _back_to_bootrom_s
>>>
>>> How does this ever get entered? If the download flag is already set
>>> prior to this code being executed, then the BROM would certainly not
>>> even come here?
>>
>> BROM would not check the boot mode register, it only enter bootrom
>> download mode if we return a non-zere value for it or it can't find a
>> valid image from all the storage
>> device.
>
> We should document this somewhere. A comment in this code might be
> great to let everyone know why we are checking this here.
>
>>>
>>> If you just always save the boot_params and check the download flag
>>> later from C code, then you could have this implemented in C. This
>>> will remove the need to write two separate assembly functions (for
>>> AArch64 and AArch32) and generally be more readable. Please revise.
>>
>> We can't predict how many settings the TPL/SPL startup code
>> changed now and future
>> will affect the bootrom download function, So back to bootrom
>> download mode before
>> anything been changed is a simple way.
>
> Ok. I’d still like to have this in C.
> The only requirement for this will be having a valid stack-pointer, so
> we should be able to do this early (before the various initialisation
> runs).
> I think board_init_f() would be a suitable place.
When I hack this function first time, I indeed wrote a c
implemented code in board_init_f on kylin-rk3036, but the usb failed
connect to my PC
when back to bootrom, after a long time checking whit the bootrom code
author, we found the interrupts related configurations are changed.
Then I try to save and restore the VBAR, then the bootrom download
function works. But when I tested this function on rk3288 based board,
it failed
again, and I found rk3288 bootrom require a different interrupt
configuration with rk3036 after a long time dig, the interrupts vector
base should be
0xffff0000(other arm32 based boards are 0x0000), so the V bit of SCTLR
should be set to 1, but the SPL startup code set it to zero.
Then I have the idea back to bootrom download mode as early as
possible when the download flag is set, Because no matter how many
parameters
I saved and restored today, no one can make sure that other parameters
will not changed by start.S in the future(maybe more properties changed
about
the interrupt, maybe the change of mmu /caches, ), because we always
have the chance to modify the startup code by the desire of new feature
or the need
to workaround something for a new soc, what's more the start.S it's now
have many #if / #else configuration, this still have risk to change the
default configurations
which will be used in bootrom download mode. If we rely on a save and
restore policy, this function may work well today, but may failed some
days later just because
some one changed another configuration in start.S.
>
>>>
>>>> +ENDPROC(check_back_to_brom_dnl_flag)
>>>> +
>>>> ENTRY(save_boot_params)
>>>> sub sp, sp, #0x60
>>>> stp x29, x30, [sp, #0x50]
>>>> @@ -23,14 +37,22 @@ ENTRY(save_boot_params)
>>>> ldr x8, =SAVE_SP_ADDR
>>>> mov x9, sp
>>>> str x9, [x8]
>>>> +#if CONFIG_ROCKCHIP_BACK_TO_BROM_DOWNLOAD_REG
>>>> + b check_back_to_brom_dnl_flag
>>>> +#else
>>>> b save_boot_params_ret /* back to my caller */
>>>> +#endif
>>>
>>> Please avoid the #if #else #endif here. Could you simply call into a
>>> function that handles this correctly for both cases?
>>
>> I have to skip the check if the REG address is zero.
>
> Good idea. Having a check for zero would match exactly how you
> described the handling of the Kconfig variable.
> Note that you should document the special meaning of zero both in a
> comment and in the Kconfig help text.
>
>>>
>>> However, this should fold back onto just the save_boot_params case
>>> anyway, if you can implement the checking function in C (as
>>> suggested above).
>>
>> Please see my explanation above.
>>>
>>>> ENDPROC(save_boot_params)
>>>>
>>>> +/*
>>>> + * x0: return value for bootrom, none-zero for bootrom download
>>>
>>> typo: non-zero
>>>
>>>> + * mode and zero for normal boot mode
>>>> + */
>>>> .globl _back_to_bootrom_s
>>>> ENTRY(_back_to_bootrom_s)
>>>> - ldr x0, =SAVE_SP_ADDR
>>>> - ldr x0, [x0]
>>>> - mov sp, x0
>>>> + ldr x1, =SAVE_SP_ADDR
>>>> + ldr x1, [x1]
>>>> + mov sp, x1
>>>> ldp x29, x30, [sp, #0x50]
>>>> ldp x27, x28, [sp, #0x40]
>>>> ldp x25, x26, [sp, #0x30]
>>>> @@ -38,7 +60,6 @@ ENTRY(_back_to_bootrom_s)
>>>> ldp x21, x22, [sp, #0x10]
>>>> ldp x19, x20, [sp]
>>>> add sp, sp, #0x60
>>>> - mov x0, xzr
>>>> ret
>>>> ENDPROC(_back_to_bootrom_s)
>>>> #else
>>>> @@ -46,6 +67,18 @@ ENDPROC(_back_to_bootrom_s)
>>>> SAVE_SP_ADDR:
>>>> .word 0
>>>>
>>>> +ENTRY(check_back_to_brom_dnl_flag)
>>>> + ldr r0, =CONFIG_ROCKCHIP_BACK_TO_BROM_DOWNLOAD_REG
>>>> + ldr r1, [r0]
>>>> + ldr r2, =BACK_TO_BROM_DOWNLOAD_FLAG
>>>> + cmp r1, r2
>>>> + bne save_boot_params_ret
>>>> + mov r3, #0
>>>> + str r3, [r0] @clear flag
>>>> + mov r0, #1 @indicate the bootrom to enter download
>>>> mode
>>>> + b _back_to_bootrom_s
>>>> +ENDPROC(check_back_to_brom_dnl_flag)
>>>
>>> See above: should be possible to do in C.
>>>
>>>> +
>>>> /*
>>>> * void save_boot_params
>>>> *
>>>> @@ -55,15 +88,21 @@ ENTRY(save_boot_params)
>>>> push {r1-r12, lr}
>>>> ldr r0, =SAVE_SP_ADDR
>>>> str sp, [r0]
>>>> - b save_boot_params_ret @ back to my caller
>>>> +#if CONFIG_ROCKCHIP_BACK_TO_BROM_DOWNLOAD_REG
>>>> + b check_back_to_brom_dnl_flag
>>>> +#else
>>>> + b save_boot_params_ret
>>>> +#endif
>>>
>>> See above.
>>>
>>>> ENDPROC(save_boot_params)
>>>>
>>>> -
>>>> +/*
>>>> + * r0: return value for bootrom, none-zero for bootrom download
>>>> + * mode and zero for normal boot mode
>>>> + */
>>>> .globl _back_to_bootrom_s
>>>> ENTRY(_back_to_bootrom_s)
>>>> - ldr r0, =SAVE_SP_ADDR
>>>> - ldr sp, [r0]
>>>> - mov r0, #0
>>>> + ldr r1, =SAVE_SP_ADDR
>>>> + ldr sp, [r1]
>>>> pop {r1-r12, pc}
>>>> ENDPROC(_back_to_bootrom_s)
>>>> #endif
>
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