Re: [PATCH v2 4/6] dt: bindings: add mt7621-pll dt binding documentation

From: Chuanhong Guo
Date: Sat Aug 17 2019 - 12:23:08 EST


On Sat, Aug 17, 2019 at 11:40 PM Oleksij Rempel <fishor@xxxxxxx> wrote:

> In provided link [0] the ralink_clk_init function is reading SYSC_REG_CPLL_CLKCFG0 R/W register.
> This register is used to determine clock source, clock freq and CPU or bus clocks.

This register should only be changed by bootloader, not kernel. So
it's read-only in kernel's perspective.

> SYSC_REG_CPLL_CLKCFG1 register is a clock gate controller. It is used to enable or disable clocks.
> Jist wild assumption. All peripheral devices are suing bus clock.

This assumption is incorrect. When this patchset is applied in
OpenWrt, I asked the author why there's still a fixed clock in
mt7621.dtsi, He told me that there's another clock for those unchanged
peripherals and he doesn't have time to write a clock provider for it.
I don't know how many undocumented clocks are there since this piece
of info is missing in datasheet.

> IMO - this information is enough to create full blown drivers/clk/mediatek/clk-mt7621.c

And this information isn't enough because the assumption above is incorrect :P

Chuanhong Guo