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[144.178.202.138]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6a3768b989fsm366900a12.10.2026.08.12.00.47.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Aug 2026 00:47:17 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 12 Aug 2026 09:47:16 +0200 Message-Id: Cc: "Mauro Carvalho Chehab" , "Rob Herring" , "Krzysztof Kozlowski" , "Conor Dooley" , =?utf-8?q?Andr=C3=A9_Apitzsch?= , "Daniel Scally" , "Bjorn Andersson" , "Konrad Dybcio" , "Eugene Lepshy" , "Vasiliy Doylov" , "Achill Gilgenast" , , , , , <~postmarketos/upstreaming@lists.sr.ht> Subject: Re: [PATCH RFT 2/3] media: i2c: dw9719: Add DW9800W support From: "Luca Weiss" To: "Danila Tikhonov" , "Griffin Kroah-Hartman" , "Sakari Ailus" , "Luca Weiss" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260801-dw9800w-clean-v1-0-38978de67963@mainlining.org> <20260801-dw9800w-clean-v1-2-38978de67963@mainlining.org> <3554d8d1-65f7-4556-8b99-1c03e0cdca53@fairphone.com> In-Reply-To: Hi Danila, On Sat Aug 8, 2026 at 2:42 PM CEST, Danila Tikhonov wrote: > 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=20 >>>>> 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=20 >>> 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 =3D 6.3 ms + SACT * 0.1 ms >>>> - LSC 1-step period =3D 252 =C2=B5s + SACT * 4 =C2=B5s >>>> >>>> Therefore, the default value may differ between the DW9800K and DW9800= W >>>> 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=20 >> structure >> and register values, including how tVIB and tLSC are calculated,=20 >> DW9800K has an extra >> register that can change the output current to 130mA but we don't ever= =20 >> use that. >> >> We didn't have a datasheet when working on the DW9800k so we had to go= =20 >> off of >> the downstream driver during runtime to get our register values. The=20 >> 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= =20 >> 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 n= o >>> device ID? >> >> Indeed, it turns out the DW9800K DOES have an info register, which=20 >> should be >> 0xEB, that's on us for not updating it after we received more=20 >> 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? Like Griffin wrote, the way the driver/bindings currently handle especially dongwoon,vcm-prescale ("vcm_freq") is completely wrong **for DW9800K**. This wasn't done better because no datasheet was available to us for the DW9800K at that point in time. Sidenote, I found a datasheet for DW9718S and that one seems to be programmed correctly. I can't comment about DW9761 and DW9719. Please wait with adding DW9800W support until this situation has been cleaned up by us since it's the same registers with both DW9800K/W. Regards Luca >> Thanks for drawing our attention to this! Nice patch. >> >> Griffin >> > --- > Best regards, > Danila