linux-kernel - Re: [PATCH RFC] media: i2c: ds90ub960: Enable second i2c interface

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Message-ID: <9032362c-a332-4b44-8c77-386edb1f09f7@ideasonboard.com>
Date: Tue, 18 Mar 2025 16:46:02 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Yemike Abhilash Chandra <y-abhilashchandra@...com>, mchehab@...nel.org
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 vaishnav.a@...com, u-kumar1@...com, r-donadkar@...com
Subject: Re: [PATCH RFC] media: i2c: ds90ub960: Enable second i2c interface

Hi,

On 05/03/2025 14:17, Yemike Abhilash Chandra wrote:
> The DS90UB960-Q1 includes a second I2C interface for independent control
> of the deserializer and remote devices. However, the current driver does
> not utilize it, thus restricting users to either CSI TX0 or CSI TX1 on
> the primary I2C interface. Enable the second I2C interface, allowing
> flexible routing where CSI TX0 can be used on the primary and CSI TX1 on
> the secondary, or vice versa by enabling appropriate ports in DT. To
> achieve the same only modify the bits relevant to the enabled RX and TX
> ports of that interface and during probe and enable_streams call, few
> registers were being reset to HW reset state, these operations are not
> necessary for functionality and resets the state when secondary I2C
> interface is probed, thus drop them.

I'm a bit confused about the description. My recollection is that both 
CSI TX0 and TX1 can be programmed just fine from the first I2C 
interface. Is that not so?

Also, even if the driver supports both CSI TXes, at the moment v4l2 
framework doesn't work with it, at least in many cases. E.g. if you 
connect one TX to a CSIRX, the other TX to another CSIRX, and those 
CSIRXes are independent, have their own media graphs, it's not going to 
work at all.

So I guess my question is, what's the target here, how did you test 
this, etc?

  Tomi