Re: [PATCH v9 01/12] dt-bindings: clk: zte: Add zx297520v3 top clock and reset controller

On Sun, Aug 02, 2026 at 11:33:33PM +0300, Stefan Dösinger wrote:
> These SoCs have 3 clock and reset controllers: Top, Matrix and LSP.
> Clocks go from oscillator -> top -> matrix -> LSP, with a register in
> top controlling most clocks that get passed to matrix and a register in
> matrix controlling all the clocks that get passed to LSP.
> 
> Generally every device has two clocks (one work clock, and one that
> connects it to the bus, I call it PCLK), two reset bits (I don't know
> what the difference is - sometimes asserting one is enough to reset the
> device, sometimes both need to be asserted). PCLK and WCLK are
> controlled by individual gates. Some devices have a mux and/or a
> divider for their work clock. Some devices, like the GPIO controller,
> only have reset bits and no clocks.
> 
> The top clock controller is fed by a 26 MHz external oscillator and has 4
> PLLs to generate other clock rates. ZTE's kernel mostly relies on the
> boot ROM to set up PLLs, but one LTE-related PLL is not configured
> on some boards. Therefore my driver contains code to program PLLs. It
> produces identical settings as the boot ROM for the pre-programmed
> frequencies.
> 
> Not all clocks will have an explicit user in the end. I am defining a
> lot of them simply to shut them off. The boot loader sets up a few of
> the proprietary timers, which will send regular IRQs (although the
> kernel of course doesn't need to listen to them). I don't plan to add a
> driver for the proprietary timer as I see no use for them - the ARM arch
> timer works just fine. I will add a driver for the very similar
> proprietary watchdog though.
> 
> The clock list in this patch is pretty complete but not exhaustive.
> There are other bits that are enabled, but I couldn't deduce what they
> are controlling by trial and error. Some of them seem to do nothing.
> Others cause an instant hang of the board when disabled. It is quite
> likely that a handful more clocks will be added in the future, but not a
> large number.
> 
> Signed-off-by: Stefan Dösinger <[email protected]>
> 
> ---
> 
> Changes v8->v9:

Reviewed-by: Krzysztof Kozlowski <[email protected]>

Best regards,
Krzysztof