linux-kernel - Re: [PATCH] arm64: dts: ti: k3-am62: use opp_efuse

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Message-ID: <20240827131342.6wrielete3yeoinl@bryanbrattlof.com>
Date: Tue, 27 Aug 2024 08:13:42 -0500
From: Bryan Brattlof <bb@...com>
To: Dhruva Gole <d-gole@...com>
CC: Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...r.kernel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Markus Schneider-Pargmann <msp@...libre.com>,
        Andrew Davis <afd@...com>, Vignesh Raghavendra <vigneshr@...com>,
        Vibhore Vardhan <vibhore@...com>
Subject: Re: [PATCH] arm64: dts: ti: k3-am62: use opp_efuse_table for
 opp-table syscon

On August 27, 2024 thus sayeth Dhruva Gole:
> Add another entry in the wkup_conf for the syscon node, and then use
> that for the syscon in opp-table.
> 
> Marking entire wkup_conf as "syscon", "simple-mfd" is wrong and needs to
> be addressed similar to how other child-nodes in wkup_conf are implemented
> in the same file.
> 
> Signed-off-by: Dhruva Gole <d-gole@...com>
> ---
> 
> Based on the discussion we had on [0] for AM62P/A devices setting OPP,
> Here we fix the AM625's opp-table using the syscon region in wkup_conf.
> 
> Build tested on top of linux-next.
> 
> Cc: Bryan Brattlof <bb@...com>
> Cc: Vignesh Raghavendra <vigneshr@...com>
> Cc: Vibhore Vardhan <vibhore@...com>
> 
> ---
> 
>  arch/arm64/boot/dts/ti/k3-am62-wakeup.dtsi | 5 +++++
>  arch/arm64/boot/dts/ti/k3-am625.dtsi       | 2 +-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-am62-wakeup.dtsi b/arch/arm64/boot/dts/ti/k3-am62-wakeup.dtsi
> index e0afafd532a5..3aff8af549a5 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62-wakeup.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62-wakeup.dtsi
> @@ -22,6 +22,11 @@ chipid: chipid@14 {
>  			reg = <0x14 0x4>;
>  		};
>  
> +		opp_efuse_table: syscon@18 {
> +			compatible = "ti,am62-opp-efuse-table", "syscon";
> +			reg = <0x18 0x4>;
> +		};
> +
>  		cpsw_mac_syscon: ethernet-mac-syscon@200 {
>  			compatible = "ti,am62p-cpsw-mac-efuse", "syscon";
>  			reg = <0x200 0x8>;
> diff --git a/arch/arm64/boot/dts/ti/k3-am625.dtsi b/arch/arm64/boot/dts/ti/k3-am625.dtsi
> index c3d1db47dc9f..c249883a8a8d 100644
> --- a/arch/arm64/boot/dts/ti/k3-am625.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am625.dtsi
> @@ -108,7 +108,7 @@ cpu3: cpu@3 {
>  	a53_opp_table: opp-table {
>  		compatible = "operating-points-v2-ti-cpu";
>  		opp-shared;
> -		syscon = <&wkup_conf>;
> +		syscon = <&opp_efuse_table>;

Ah I wish it was as easy as this. Unfortunately ti-cpufreq.c embeds the 
0x18 offset from the start of the WKUP_CRTL_MMR to get to the 
JTAG_USER_ID[0] for the AM62x. For the AM62Ax and AM62Px I used a 0x0 
offset which is why this works for them. (Essentially hacking around the 
issue until I could find a way to fix this)

I think we may need some coordination between the different maintainers 
to get this fixed without breaking DFS for the AM62x for a release. That 
or we could add some logic in the driver to check for an offset in this 
property eg: 'syscon = <&opp_efuse_table 0x18>;' and use that. The end 
goal is to not need the offset at all so this is a lot of noise 
generation just to keep things working while we clean it up.

All of the solutions I can think of are super messy unfortunately.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/cpufreq/ti-cpufreq.c#n302

~Bryan