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

[Griffin Kroah-Hartman <griffin.kroah@fairphone.com>]

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.

> 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.

Thanks for drawing our attention to this! Nice patch.

Griffin