Re: [PATCH] arm64: dts: ti: k3-am62: use opp_efuse_table for opp-table syscon

From: Bryan Brattlof
Date: Tue Aug 27 2024 - 09:15:25 EST


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@xxxxxx>
> ---
>
> 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@xxxxxx>
> Cc: Vignesh Raghavendra <vigneshr@xxxxxx>
> Cc: Vibhore Vardhan <vibhore@xxxxxx>
>
> ---
>
> 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