linux-kernel - Re: [PATCH 0/3] Convert clk-fixed into module platform driver

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Date:	Wed, 15 Jun 2016 00:59:15 +0200
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Michael Turquette <mturquette@...libre.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	jeremy.kerr@...onical.com, linux-clk@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Convert clk-fixed into module platform driver

Hi Stephen

Assume this device tree overlay:


&bus0{

axi_clk: axi_clk {
compatible = "fixed-clock";
#clock-cells = <0x0>;
clock-frequency = <125000000>;
};

iic_0: iic {
#address-cells = <1>;
#size-cells = <1>;
compatible = "xlnx,xps-iic-2.00.a";
reg = < 0x00030000 0x10000 >;
interrupt-parent = <&xps_intc_0>;
interrupts = < 2 2 >;
clocks = <&axi_clk>;
 } ;

}

Which is basically a new i2c master and a fixed clock definition.

The fixed clock driver will only be probed to the driver at arch
initialization, when of_clk_init is called.  The device overlay can be
added at any point, usually after arch init. Which will result in ii_0
failing to probe,  because it is missing its clock.

This changeset allows fixed clocks to be added after of_clk_init is
called, by converting the driver into a platform driver.


Thanks!b

On Tue, Jun 14, 2016 at 7:39 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 06/08, Ricardo Ribalda Delgado wrote:
>> When clock providers are added to the device tree after of_clk_init is called
>> they are not added to the clock provider list. This makes that drivers such
>> as i2c-xiic.c fail to init, as they may depend on the unadded clock provider.
>
> Who's the provider here? It isn't clear to me why we're
> populating fixed factor and fixed rate clks from DT for i2c
> devices? Presumably there's an i2c device driver that should be
> populating clks from C code instead?
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project



-- 
Ricardo Ribalda