linux-kernel - Re: [PATCH 0/3] Apple M1 clock gate driver

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Message-Id: <02176203-7f29-4ff4-933b-70235cf0dd22@www.fastmail.com>
Date:   Sat, 05 Jun 2021 14:12:31 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Tony Lindgren" <tony@...mide.com>
Cc:     "Rob Herring" <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hector Martin" <marcan@...can.st>,
        "Michael Turquette" <mturquette@...libre.com>,
        "Stephen Boyd" <sboyd@...nel.org>,
        "Mark Kettenis" <mark.kettenis@...all.nl>,
        "Arnd Bergmann" <arnd@...nel.org>
Subject: Re: [PATCH 0/3] Apple M1 clock gate driver

Hi Tony,

On Fri, Jun 4, 2021, at 09:43, Tony Lindgren wrote:
> Hi,
> 
> How about the following where you set up the gate clocks as separate 
> child nodes:
> 
> pmgr0: clock-controller@...700000 {
> 	compatible = "apple,foo-clock-controller";
> 	#clock-cells = <1>;
> 	reg = <0x2 0x3b700000 0x0 0x4000>;
> 
> 	clk_uart0: clock@270 {
> 		compatible = "apple,t8103-gate-clock";
> 		#clock-cells = <0>;
> 		assigned-clock-parents = <&pmgr0 APPLE_CLK_SIO>,
> 					 <&pmgr0 APPLE_CLK_UART_P>;
> 		// ...
> 	};
> 
> };
> 
> Keep the clock controller still addressable by offset from base as discussed,
> and additionally have the driver parse and set up the child node clocks.

Nice, I like that one even better! We can keep the internal clocks "hidden"
inside the parent node and only need to model the actual consumer clocks
as separate nodes.

Are you aware of any clock driver that implements something similar?
I'd like to avoid reinventing the wheel if it's already been done before.

> 
> Then I think the consumer driver can just do:
> 
> serial0: serial@...200000 {
> 	// ...
> 	clocks = <&clk_uart0>, <&clk24>;
> 	clock-names = "uart", "clk_uart_baud0";
> 	// ...
> };
> 
> Regards,
> 
> Tony
> 

Best,

Sven