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Date:   Thu, 26 Oct 2017 11:25:44 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     <linux-clk@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>
CC:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-snps-arc@...ts.infradead.org>,
        "Mark Rutland" <mark.rutland@....com>
Subject: Re: [PATCH] CLK: ARC: Set initial pll output frequency specified in
 device tree

Hi folks,


On 09/29/2017 06:13 AM, Eugeniy Paltsev wrote:
> Add option to set initial output frequency of plls via
> "clock-frequency" property in pll's device tree node.
> This frequency will be set while pll driver probed.
> 
> The usage example is setting CPU clock frequency on boot
> See discussion:
> https://www.mail-archive.com/linux-snps-arc@lists.infradead.org/msg02689.html

Any yay / nay on this please ?

I guess some de-duplication is in order anyways but is the overall approach sane ?

Additional background / context in thread
http://lists.infradead.org/pipermail/linux-snps-arc/2017-September/002900.html

Thx,
-Vineet



> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>   .../bindings/clock/snps,hsdk-pll-clock.txt         |  5 ++++
>   .../devicetree/bindings/clock/snps,pll-clock.txt   |  5 ++++
>   drivers/clk/axs10x/pll_clock.c                     | 34 ++++++++++++++++++++--
>   drivers/clk/clk-hsdk-pll.c                         | 34 ++++++++++++++++++++--
>   4 files changed, 74 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt b/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
> index c56c755..5703059 100644
> --- a/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
> @@ -13,6 +13,10 @@ Required properties:
>   - clocks: shall be the input parent clock phandle for the PLL.
>   - #clock-cells: from common clock binding; Should always be set to 0.
>   
> +Optional properties:
> +- clock-frequency: output frequency generated by pll in Hz which will be set
> +while probing. Should be a single cell.
> +
>   Example:
>   	input_clk: input-clk {
>   		clock-frequency = <33333333>;
> @@ -25,4 +29,5 @@ Example:
>   		reg = <0x00 0x10>;
>   		#clock-cells = <0>;
>   		clocks = <&input_clk>;
> +		clock-frequency = <1000000000>;
>   	};
> diff --git a/Documentation/devicetree/bindings/clock/snps,pll-clock.txt b/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
> index 11fe487..5908f99 100644
> --- a/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
> @@ -13,6 +13,10 @@ registers and second for corresponding LOCK CGU register.
>   - clocks: shall be the input parent clock phandle for the PLL.
>   - #clock-cells: from common clock binding; Should always be set to 0.
>   
> +Optional properties:
> +- clock-frequency: output frequency generated by pll in Hz which will be set
> +while probing. Should be a single cell.
> +
>   Example:
>   	input-clk: input-clk {
>   		clock-frequency = <33333333>;
> @@ -25,4 +29,5 @@ Example:
>   		reg = <0x80 0x10>, <0x100 0x10>;
>   		#clock-cells = <0>;
>   		clocks = <&input-clk>;
> +		clock-frequency = <100000000>;
>   	};
> diff --git a/drivers/clk/axs10x/pll_clock.c b/drivers/clk/axs10x/pll_clock.c
> index 25d8c24..3f4345d 100644
> --- a/drivers/clk/axs10x/pll_clock.c
> +++ b/drivers/clk/axs10x/pll_clock.c
> @@ -11,6 +11,7 @@
>   #include <linux/platform_device.h>
>   #include <linux/module.h>
>   #include <linux/clk-provider.h>
> +#include <linux/clk.h>
>   #include <linux/delay.h>
>   #include <linux/err.h>
>   #include <linux/device.h>
> @@ -215,6 +216,25 @@ static const struct clk_ops axs10x_pll_ops = {
>   	.set_rate = axs10x_pll_set_rate,
>   };
>   
> +static void set_pll_rate_from_of(struct clk *clk, struct device_node *node)
> +{
> +	u32 requested_rate;
> +
> +	/* If we specify initial pll output frequency try to set it */
> +	if (of_property_read_u32(node, "clock-frequency", &requested_rate))
> +		return;
> +
> +	if (clk_prepare_enable(clk)) {
> +		pr_err("Cannot enable %s clock.\n", node->name);
> +		return;
> +	}
> +
> +	if (clk_set_rate(clk, requested_rate))
> +		pr_err("Cannot set %s clock rate.\n", node->name);
> +
> +	pr_debug("Set %s clock to %u\n", node->name, requested_rate);
> +}
> +
>   static int axs10x_pll_clk_probe(struct platform_device *pdev)
>   {
>   	struct device *dev = &pdev->dev;
> @@ -258,8 +278,15 @@ static int axs10x_pll_clk_probe(struct platform_device *pdev)
>   		return ret;
>   	}
>   
> -	return of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
> -			&pll_clk->hw);
> +	ret =  of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
> +				      &pll_clk->hw);
> +	if (ret)
> +		return ret;
> +
> +	/* If we specify initial pll output frequency in dts try to set it */
> +	set_pll_rate_from_of(pll_clk->hw.clk, dev->of_node);
> +
> +	return 0;
>   }
>   
>   static int axs10x_pll_clk_remove(struct platform_device *pdev)
> @@ -311,6 +338,9 @@ static void __init of_axs10x_pll_clk_setup(struct device_node *node)
>   		goto err_unregister_clk;
>   	}
>   
> +	/* If we specify initial pll output frequency in dts try to set it */
> +	set_pll_rate_from_of(pll_clk->hw.clk, node);
> +
>   	return;
>   
>   err_unregister_clk:
> diff --git a/drivers/clk/clk-hsdk-pll.c b/drivers/clk/clk-hsdk-pll.c
> index bbf23717..74fd006 100644
> --- a/drivers/clk/clk-hsdk-pll.c
> +++ b/drivers/clk/clk-hsdk-pll.c
> @@ -9,6 +9,7 @@
>    */
>   
>   #include <linux/clk-provider.h>
> +#include <linux/clk.h>
>   #include <linux/delay.h>
>   #include <linux/device.h>
>   #include <linux/err.h>
> @@ -295,6 +296,25 @@ static const struct clk_ops hsdk_pll_ops = {
>   	.set_rate = hsdk_pll_set_rate,
>   };
>   
> +static void set_pll_rate_from_of(struct clk *clk, struct device_node *node)
> +{
> +	u32 requested_rate;
> +
> +	/* If we specify initial pll output frequency try to set it */
> +	if (of_property_read_u32(node, "clock-frequency", &requested_rate))
> +		return;
> +
> +	if (clk_prepare_enable(clk)) {
> +		pr_err("Cannot enable %s clock.\n", node->name);
> +		return;
> +	}
> +
> +	if (clk_set_rate(clk, requested_rate))
> +		pr_err("Cannot set %s clock rate.\n", node->name);
> +
> +	pr_debug("Set %s clock to %u\n", node->name, requested_rate);
> +}
> +
>   static int hsdk_pll_clk_probe(struct platform_device *pdev)
>   {
>   	int ret;
> @@ -340,8 +360,15 @@ static int hsdk_pll_clk_probe(struct platform_device *pdev)
>   		return ret;
>   	}
>   
> -	return of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
> -			&pll_clk->hw);
> +	ret =  of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
> +				      &pll_clk->hw);
> +	if (ret)
> +		return ret;
> +
> +	/* If we specify initial pll output frequency in dts try to set it */
> +	set_pll_rate_from_of(pll_clk->hw.clk, dev->of_node);
> +
> +	return 0;
>   }
>   
>   static int hsdk_pll_clk_remove(struct platform_device *pdev)
> @@ -400,6 +427,9 @@ static void __init of_hsdk_pll_clk_setup(struct device_node *node)
>   		goto err_unmap_spec_regs;
>   	}
>   
> +	/* If we specify initial pll output frequency in dts try to set it */
> +	set_pll_rate_from_of(pll_clk->hw.clk, node);
> +
>   	return;
>   
>   err_unmap_spec_regs:
> 

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