[PATCH] mtd: spi-nor-core: call WATCHDOG_RESET() in spi_nor_ready()

[Vignesh Raghavendra]

On 19/03/20 5:09 pm, Rasmus Villemoes wrote:
> On 19/03/2020 12.25, Vignesh Raghavendra wrote:
>> Hi,
[...]
>>> @@ -399,6 +400,7 @@ static int spi_nor_ready(struct spi_nor *nor)
>>>  {
>>>  	int sr, fsr;
>>>  
>>> +	WATCHDOG_RESET();
>>
>> Is it necessary to reset watchdog for every status register read? How
>> small is the timeout? Resetting too often will impact performance
>> depending on overhead of this call.
>>
>> Is it not sufficient to reset watchdog once per page write (in
>> spi_nor_write()) and once per sector erase (in spi_nor_erase())?
>>
> 
> Probably, yes. I was a bit torn between putting the call here or in
> spi_nor_wait_till_ready(). That should do it once per erase/page write
> which should be fine (well, if the busy-looping for spi_nor_ready takes
> more than the watchdog timeout, the board will reset, but I don't think
> the flash is that bad).>
> I'll test that, but I just found out I'll need something in the read
> path as well. Reading 1MB works fine, reading 2MB resets:
> 
> [2020-03-19 12:31:11.923] => echo a ; sf read $loadaddr 0 0x100000 ; echo b
> [2020-03-19 12:31:32.724] a
> [2020-03-19 12:31:32.724] device 0 offset 0x0, size 0x100000
> [2020-03-19 12:31:33.586] SF: 1048576 bytes @ 0x0 Read: OK
> [2020-03-19 12:31:33.586] b
> [2020-03-19 12:31:33.586] => echo a ; sf read $loadaddr 0 0x200000 ; echo b
> [2020-03-19 12:31:40.771] a
> [2020-03-19 12:31:40.771] device 0 offset 0x0, size 0x200000
> [2020-03-19 12:31:42.666]
> [2020-03-19 12:31:42.666] U-Boot SPL 2020.01-00078-g058da1a-dirty (Mar
> 17 2020 - 16:27:58 +0000)
> 

Hmm, Watchdog seems to be set to trigger after ~2s of inactivity. Isn't
that too small? WATCHDOG_RESET() resets only once per second, so 2
second timeout is too close IMO.

Typical watchdog timeouts are usually in tens of seconds