[+ clock maintainers] On 6/13/22 6:17 AM, Andre Przywara wrote: > On Sun, 12 Jun 2022 23:09:07 +0200 > Jernej Škrabec <jernej.skrabec@xxxxxxxxx> wrote: > > Hi Samuel, > >> Dne torek, 31. maj 2022 ob 06:50:35 CEST je Samuel Holland napisal(a): >>> This series is preparation for converting the PRCM MFD and legacy clock >>> drivers to a CCU clock driver. > > May I ask what the purpose of this exercise is? So if I understand > correctly, then it's about to convert the sun8i-a23-prcm MFD driver and > its children to a single "modern style" CCU clock driver, with its opaque > DT node? Yes, the purpose is to finish the conversion that was started six years ago[1][2], and eventually delete drivers/clk/sunxi. [1]: https://git.kernel.org/torvalds/c/78a9f0dbcd60 [2]: https://git.kernel.org/torvalds/c/2c89ce4f4b19 > If that changes the compatible strings or the references to the clock > providers (and I guess it would need to?), then this would mean an > incompatible change. Which also means we would need to keep the old code > around, to maintain compatibility with "old" DTs? So what is the win then? > Now we have *two* clock drivers, for the same device, which need > maintenance and testing. We already have two drivers for the PRCM. ccu-sun8i-r, which is already built in to all MACH_SUN8I kernels, was originally intended to support A31/A23/A33, but nobody ever implemented it. See the comment in the binding header: /* 8 is reserved for CLK_APB0_W1 on A31 */ The benefits of conversion are: - U-Boot does not have to add support for an already-deprecated clock framework. - Users who know they have a recent devicetree can disable CLK_SUNXI. - Eventually we can disable CLK_SUNXI and delete drivers/clk/sunxi. Yes, we need to keep the old code for several years to support existing devicetrees. That is exactly why I want to do the conversion as soon as possible: to get that clock started now. > So can you confirm that this will be a breaking change? Yes, just like the other half of the CCU conversion was. >> The platform SMP code references the PRCM >>> node to map its MMIO space, which will break when the PRCM node is >>> removed/replaced. >> >> Why can't we just leave old platform code? If older dtb file is used, it would >> still work. Actually, isn't trivial to support new CCU binding too, just by >> including new CCU compatible string? IIUC new CCU node will have same address >> as current PRCM node. Yes, I could add the new compatible. I was trying to avoid adding more code and more complexity to code that appeared to be unused in the first place. > This aims for a similar direction, though in this case the alternative > (PSCI) predates the sunxi specific method in the kernel support. Can we > just deprecate this code, maybe issue a warning, with the hint to update > the bootloader (which might not be possible for some devices)? Since mainline U-Boot provides PSCI, I assume the purpose of this code was to support the vendor bootloader blob. And the threads adding this code[3][4] confirm that. In that case, users would have to be using a DTB shipped with the kernel, not the one provided by the bootloader. So if we change the devicetree, we have to change the code, too. Regards, Samuel [3]: https://lore.kernel.org/lkml/20131110100312.GI26440@lukather/ [4]: https://lore.kernel.org/lkml/1426649042-30547-1-git-send-email-wens@xxxxxxxx/ > Cheers, > Andre > >> Best regards, >> Jernej >> >>> >>> Since PSCI has been available for 7+ years, instead of trying to deal >>> with the migration, I think it's safe to just delete this code. >>> >>> >>> Samuel Holland (3): >>> ARM: sunxi: Remove A31 and A23/A33 platform SMP code >>> ARM: dts: sunxi: Remove obsolete CPU enable methods >>> dt-bindings: arm: Remove obsolete CPU enable methods >>> >>> .../devicetree/bindings/arm/cpus.yaml | 2 - >>> arch/arm/boot/dts/sun6i-a31.dtsi | 1 - >>> arch/arm/boot/dts/sun8i-a23-a33.dtsi | 1 - >>> arch/arm/mach-sunxi/Makefile | 1 - >>> arch/arm/mach-sunxi/platsmp.c | 194 ------------------ >>> 5 files changed, 199 deletions(-) >>> delete mode 100644 arch/arm/mach-sunxi/platsmp.c >>> >>> -- >>> 2.35.1
