linux-kernel - Re: [PATCH v3 1/8] arm64: dts: ti: k3-am62x-sk-common: Update main-i2c1 frequency

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Date:   Sun, 30 Jul 2023 11:30:52 -0500
From:   Nishanth Menon <nm@...com>
To:     Aradhya Bhatia <a-bhatia1@...com>
CC:     Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Conor Dooley <conor+dt@...nel.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        Rahul T R <r-ravikumar@...com>,
        Devarsh Thakkar <devarsht@...com>,
        Jai Luthra <j-luthra@...com>,
        Jayesh Choudhary <j-choudhary@...com>
Subject: Re: [PATCH v3 1/8] arm64: dts: ti: k3-am62x-sk-common: Update
 main-i2c1 frequency

On 23:04-20230728, Aradhya Bhatia wrote:
> The Display Data Channel (DDC) transactions between an HDMI transmitter
> (SIL9022A in this case) and an HDMI monitor, occur at a maximum of
> 100KHz. That's the maximum supported frequency within DDC standards.
> 
> While the SIL9022A can transact with the core at 400KHz, it needs to
> drop the frequency to 100KHz when communicating with the monitor,
> otherwise, the i2c controller times out and shows warning like this.
> 
> [  985.773431] omap_i2c 20010000.i2c: controller timed out
> 
> That feature, however, has not been enabled in the SIL9022 driver.
> 
> Since, dropping the frequency doesn't affect any other devices on the
> bus, drop the main-i2c1 frequency from 400KHz to 100KHz.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>  arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> index 34c8ffc553ec..540ed8a0d7fb 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> @@ -300,7 +300,7 @@ &main_i2c1 {
>  	status = "okay";
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&main_i2c1_pins_default>;
> -	clock-frequency = <400000>;
> +	clock-frequency = <100000>;
>  
>  	tlv320aic3106: audio-codec@1b {
>  		#sound-dai-cells = <0>;
> -- 
> 2.40.1
> 

I know we had issues with level shifters on the dev platform previously,
but do we need this patch anymore with the production boards?

if so, use Fixes and I can pick for next.

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D