Re: [PATCH v2 06/12] mfd: sec: add support for S2MU005 PMIC

[Kaustabh Chakraborty]

On 2026-02-20 17:56 +01:00, Sander Vanheule wrote:
> Hi,
>
> On Thu, 2026-02-05 at 21:02 +0530, Kaustabh Chakraborty wrote:
>> On 2026-02-04 15:23 +00:00, André Draszik wrote:
>> > On Mon, 2026-01-26 at 00:37 +0530, Kaustabh Chakraborty wrote:
>> > > +static const struct regmap_config s2mu005_regmap_config = {
>> > > +	.reg_bits = 8,
>> > > +	.val_bits = 8,
>> > > +};
>> > 
>> > No cache? And what is the .max_register value?
>> > 
>> 
>> This was in the previous revision, but I ended up removing it because
>> (at least I thought at that time) interfered with interrupts firing in
>> some way. The actual issue was unrelated, so I will add it back.
>> 
>> However, there is also another thing I see in logs:
>> 
>> sec-pmic-i2c 2-003d: using zero-initialized flat cache, this may cause
>> unexpected behavior
>> 
>> This is due to REGCACHE_FLAT, I am not sure if I should just ignore
>> this.
>
> Sorry to be late to the party, but I'm somewhat responsible for that warning, so
> allow me to chime in :-)
>
> What you are might have been seeing is REGCACHE_FLAT giving you "cached" values
> of 0x0, while the hardware actually has something else. This can cause omitted
> writes, existing (bootloader) config to overwritten, etc.
>
> As André suggested, using .num_reg_defaults_raw is a possibility, but then you
> have to remember that the register defaults are taken to be what the hardware
> state is at that moment, including pre-probe changes. These defaults are used to
> seed the cache (so far, so good), but this may break the contract of
> regmap_sync() if you ever want to use that after actually resetting the PMIC.
>
> If you want to use the flat cache, I would suggest you use REGCACHE_FLAT_S,
> which will track what has already been read from/written to hardware. You will
> also need to specifiy .max_register.

I had figured that out by going through the logs, thanks. :)

>
> I see the other regmap_config-s in this driver also use REGCACHE_FLAT, so you
> may want to consider switching those over as well if these are also showing the
> new warning.
>
>
> Best,
> Sander