[External] aspeed: spi driver: fmc wdt2

[健张]

> 2022年4月28日 09:17，Joel Stanley <joel at jms.id.au> 写道：
> 
> On Tue, 26 Apr 2022 at 14:09, 张健 <zhangjian.3032 at bytedance.com> wrote:
>> 
>> Hi Guys;
>> 
>> I would like implement the flash toggle function in ast2600.
>> That function about ast2400/2500 implement at linux/aspeed_wdt.c at aspeed-master-v5.15 · AspeedTech-BMC/linux (github.com)
>> 
>> Here is my design, just an idea. I would like to see your suggestions. Thanks.
>> 
>> There are some differences between ast2600 and ast2500/2400. For the ast2600 SoC abr function, there is a set of registers named `FMC_WDT2` in FMC(SPI).
>> FMC_WDT2 is not a full function WDT, thus, I can't use aspeed_wdt driver to do that.
> 
> Yes. There is a similar device embedded in the secure boot controller
> for eMMC boot (SECA0..A8). The FMC register is better documented, but
> the layout is the same.
> 
>> In ast2400/2500 used a sysfs attr `access_cs0`, can make cs0->cs1 and cs1->cs0.
>> For cs0->cs1, ast2400/2500 use the wdt2's self timer, cs1->cs0, use `access_cs0` to set the `flash indicate` bit.
>> But ast2600 without the FMC_WDT2 timer driver to trigger `cs0`->`cs1`, thus, I would like to add 2 sysfs attrs in spi driver.
>> Because ast2600 supports single image abr mode, i'd like to use primary/backup instead of cs0/1.
> 
> Does the ast2400/ast2500 method cs0/cs1 method work on 2600 too? If
> so, should we enable the boot switch sysfs files for 2600 too?
   
   Yes, Maybe the sysfs file will be a little different.
> 
> Regarding the abr mode, could we create a piece of shared code that is
> used by both the FMC and SEC. It would be called by the respective
> drivers to register the sysfs files, with a pointer to the appropriate
> registers
   
   Just read SECA0_A8, They are exactly the same, I think it’s okay.
> 
>> attr1 "access_backup": (only appears in primary and compatible is "aspeed,ast2600-fmc")
>> store: The parameter is the timeout time for fmc_wdt2, if written, timer will be enabled, if timeout, will reboot from backup.
>> show: the time left in fmc_wdt2 timer. 0 means timer is not enabled.
>> 
>> attr2 "access_primary”: (only appears in backup, and compatible is "aspeed,ast2600-fmc")
>> store: Non-zero values indicate access to primary, 0 indicate access to backup
>> show: 0: next reboot will boot from backup, 1 : will boot from primary.
> 
> I think this makes sense. I'd suggest coding it up and putting it on
> the list. As Cédric mentioned, adding support to Qemu would be useful
> for testing too.

I’ll do that asap.
> 
> A separate concern is adding support to u-boot, so u-boot can pat the
> watchdog in early boot (and when sitting at the u-boot prompt).
> 

> Thanks for sending your proposal along.
> 
> Cheers,
> 
> Joel