On Tue, 13 Jun 2023 18:41:15 +0200, Mark Brown wrote: > > On Tue, Jun 13, 2023 at 06:15:12PM +0200, Takashi Iwai wrote: > > Mark Brown wrote: > > > On Tue, Jun 13, 2023 at 04:24:28PM +0200, Takashi Iwai wrote: > > > > > Since HD-audio codec has no known default values unlike normal codecs, > > > > it needs to initialize itself only at the first access, and this > > > > helper does it. > > > > Ah, if it's just suppressing the write the code should just be removed. > > > regmap_update_bits() already suppresses noop writes so unless we might > > > write a different value to the register later the effect will be the > > > same. I can send a patch. > > > Oh, I'm afraid that we're seeing different things. The code there is > > rather to *set* some initial value for each amp register (but only > > once), and it's not about optimization for writing a same value > > again. > > > That is, the function helps to set an initial (mute) value on each amp > > when the driver parses the topology and finds an amp. But if the > > driver already has parsed this amp beforehand by other paths, it skips > > the initialization, as the other path may have already unmuted the > > amp. > > > Or I might have misunderstood what you mean about _update_bits()... > > So it is possible that we might set two distinct values during setup > then and we're doing this intentionally? It's not obvious that this > might happen. A comment wouldn't hurt, and a big part of this is > confusing is that in the non-regmap case all we're doing is suppressing > duplicate writes, in that path it's just checking for changes in the > register value. > > None of this is what the non-regmap path does, it just suppresses noop > writes to the hardware. Actually, many of HD-audio codec driver code heavily relies on the regmap, more or less mandatory. The snd_hda_codec_amp_init() is one of such. You may write a codec driver without the regmap, but some helpers won't work as expected. Takashi
