Re: [PATCH RFT 2/3] media: i2c: dw9719: Add DW9800W support

[Danila Tikhonov]

Hi Griffin, Sakari,

Thank you for the clarification.

On 07/08/2026 17:30, Griffin Kroah-Hartman wrote:
> Hello Sakari, Danilla,
>
> On 05/08/2026 13:29, Sakari Ailus wrote:
> > Hi Danila, Griffin,
> >
> > On Tue, Aug 04, 2026 at 09:27:01PM +0300, Danila Tikhonov wrote:
> > > Hi Sakari,
> > >
> > > Thank you for your comment.
> > >
> > > On 04/08/2026 11:40, Sakari Ailus wrote:
> > > > Hi Danila,
> > > >
> > > > Thank you for the patch.
> > > >
> > > > On Sat, Aug 01, 2026 at 09:04:15PM +0300, Danila Tikhonov wrote:
> > > > > The DW9800W uses the same chip ID and register layout as the DW9800K,
> > > > > but requires different default VCM frequency value.
> > > > Is this a real difference between the two models or what fits for the
> > > > attached lens? Too bad the datasheet isn't publicly available. :-(
> > > >
> > > > At least the differing default and constraints for 
> > > > dongwoon,vcm-prescale
> > > > needs to be documented in bindings.
> > > I share your skepticism and have essentially the same concerns. Since I
> > > do not have the DW9800K datasheet, I cannot say with certainty how it
> > > differs from the DW9800W.
> > Indeed. The limits should have been added for dw9800k, too, but I 
> > guess I
> > missed this in review. :-\
> >
> > > In particular, the parameter referred to as the VCM frequency in the
> > > driver is used to derive the SACT value. For the DW9800W, SACT[5:0]
> > > defines the actuator resonance period in SAC mode and the one-step
> > > period in LSC mode. The datasheet gives the corresponding formulas as:
> > > - tVIB = 6.3 ms + SACT * 0.1 ms
> > > - LSC 1-step period = 252 µs + SACT * 4 µs
> > >
> > > Therefore, the default value may differ between the DW9800K and DW9800W
> > > if the formulas or timing characteristics used to calculate SACT are
> > > different.
> > Griffin, would you be able to comment this?
>
> After checking on my side, DW9800W and K are almost identical in both 
> structure
> and register values, including how tVIB and tLSC are calculated, 
> DW9800K has an extra
> register that can change the output current to 130mA but we don't ever 
> use that.
>
> We didn't have a datasheet when working on the DW9800k so we had to go 
> off of
> the downstream driver during runtime to get our register values. The 
> datasheet is a
> much more reliable source to be using for this instead.
>
> My colleague has already identified ways to fix the bindings, which we 
> will
> tackle ourselves.
I'm glad you were able to clarify the situation, as this should help us
handle both IC variants correctly.
> > Another matter: the comment on dw9800k says there's no device ID. So is
> > there a device ID that wasn't just checked earlier or is there really no
> > device ID?
>
> Indeed, it turns out the DW9800K DOES have an info register, which 
> should be
> 0xEB, that's on us for not updating it after we received more 
> documentation.
Given this, and assuming everyone agrees, I think it would make sense
for me to leave the DW9800K untouched in the next version of this patch
series. Since it turns out that the DW9800K has a different Chip ID, you
can fix the Chip ID check for it separately based on the information you
have.

One point is still unclear to me, though: is the default VCM frequency
the same for both ICs, or does it differ between them?

> Thanks for drawing our attention to this! Nice patch.
>
> Griffin
---
Best regards,
Danila