Re: [PATCH] arm64: dts: monaco: Fix CSI I2C controllers default bus frequency

On 7/24/26 17:22, Hans de Goede wrote:
> Hi,
> 
> On 24-Jul-26 1:42 PM, Konrad Dybcio wrote:
>> On 7/23/26 1:48 PM, Hans de Goede wrote:
>>> 1 MHz is quite fast for an I2C bus and not necessarly reliable, change this
>>> to 400 KHz which is a more reasonable default.
>>>
>>> Signed-off-by: Hans de Goede <[email protected]>
>>
>>
>> I guess this is a question of what's more common among client
>> devices. I assume you have some that aren't happy with 1 MHz?
> 
> Looking at ACPI tables for many x86 devices 400 KHz is the standard,
> with some devices going down to 100 KHz. 1 MHz is pretty much
> unheard off.
> 
> Note the official I2C spec is limited to 100 KHz anything faster then
> that is an extension.
> 
> My specific reason for submitting this patch is imx219 sensors on
> Mona sometimes failing to initialize at 1MHz which is kinda to
> be expected when going for 10x the I2C specification max value.
> 

1 MHz I2C bus speed is in the v3 of the I2C specification dated 2007,
its name is Fast-mode Plus (Fm+), thus the statement above is invalid.

As it's been said on the list recently likely the problem with sensor
controls on a number of platforms is due to invalid setting of I2C bus
speeds, e.g. out-of-spec 512 KHz I2C bus speed instead of wanted 1 MHz,
or 204.8 KHz I2C bus speed instead of 400 KHz, which is done by this
applied change.

The list of affected platform .dtsi files is:
* kodiak.dtsi
* lemans.dtsi
* milos.dtsi
* monaco.dtsi
* sc8280xp.dtsi
* sdm670.dtsi
* sm8250.dtsi
* sm8450.dtsi
* sm8550.dtsi
* sm8650.dtsi
* talos.dtsi

An example of a "fix" (it's not a fix, but a simple workaround of
the flaw in the driver) for SM8650 and other platforms can be like
the one recently published:

https://lore.kernel.org/linux-arm-msm/[email protected]

-- 
Best wishes,
Vladimir