Re: [PATCH] regmap: support regmap_field_write() on non-readable fields

[Mark Brown]

On Tue, Jul 19, 2022 at 12:54:02PM +0000, Charles Keepax wrote:
> On Tue, Jul 19, 2022 at 02:14:46PM +0200, Krzysztof Kozlowski wrote:

> > +	if (regmap_readable(field->regmap, field->reg))
> > +		return regmap_update_bits_base(field->regmap, field->reg,
> > +					       mask, val << field->shift,
> > +					       change, async, force);

> I think this will break other valid use-cases, regmap_readable (I
> believe) returns if the register is physically readable, however
> it should still be possible to use update bits if the register is
> in the cache even if it can't physically be read. So really you
> need to fall into this path if it is readable or in the cache.

This is true, we don't currently have a readable_or_cached() check -
this is implemented as trying the cache and only considering actually
reading if there's a read, effectively what we want to do here is force
a cache only read.

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