linux-kernel - Re: [PATCH v3 3/5] clk: add support for clocks provided by SCP(System Control Processor)

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Message-ID: <55716DA4.2090003@arm.com>
Date:	Fri, 05 Jun 2015 10:36:36 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Kevin Hilman <khilman@...nel.org>,
	Olof Johansson <olof@...om.net>,
	Mike Turquette <mturquette@...aro.org>
Subject: Re: [PATCH v3 3/5] clk: add support for clocks provided by SCP(System
 Control Processor)



On 04/06/15 21:20, Stephen Boyd wrote:
> On 05/27, Sudeep Holla wrote:
>> +
>> +#include <linux/clk-provider.h>
>> +#include <linux/device.h>
>> +#include <linux/err.h>
>> +#include <linux/of.h>
>> +#include <linux/module.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/scpi_protocol.h>
>> +
>> +struct scpi_clk {
>> +	u32 id;
>> +	const char *name;
>> +	struct clk_hw hw;
>> +	struct scpi_dvfs_info *info;
>> +	unsigned long rate_min;
>> +	unsigned long rate_max;
>> +};
>> +
>> +#define to_scpi_clk(clk) container_of(clk, struct scpi_clk, hw)
>> +
>> +static struct scpi_ops *scpi_ops;
>
> Why do we need this singleton? Can we put this pointer into scpi_clk?
>

Yes I will move it.

>> +
>> +static unsigned long scpi_clk_recalc_rate(struct clk_hw *hw,
>> +					  unsigned long parent_rate)
>> +{
>> +	struct scpi_clk *clk = to_scpi_clk(hw);
>> +
>> +	return scpi_ops->clk_get_val(clk->id);
>> +}
>> +
>> +static long scpi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
>> +				unsigned long *parent_rate)
>> +{
>> +	struct scpi_clk *clk = to_scpi_clk(hw);
>> +
>> +	if (WARN_ON(clk->rate_min && rate < clk->rate_min))
>> +		rate = clk->rate_min;
>> +	if (WARN_ON(clk->rate_max && rate > clk->rate_max))
>> +		rate = clk->rate_max;
>> +
>> +	return rate;
>> +}
>
> Hm.. this seems really generic. It might be better to support a
> way to tell the framework to limit the min/max rate that's
> accepted for a clk. That could be done later though.
>

True, framework have some boundary checks in place. I will check if
I can use it with minimum changes to the core. If not, we can take this
up later as you suggested.

>> +
>> +static int scpi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
>> +			     unsigned long parent_rate)
>> +{
>> +	struct scpi_clk *clk = to_scpi_clk(hw);
>> +
>> +	return scpi_ops->clk_set_val(clk->id, rate);
>> +}
>> +
> [..]
>> +
>> +static int scpi_clk_add(struct device *dev, struct device_node *np)
>> +{
>> +	struct clk **clks;
>> +	int idx, count;
>> +	struct clk_onecell_data *clk_data;
>> +
>> +	count = of_property_count_strings(np, "clock-output-names");
>> +	if (count < 0) {
>> +		dev_err(dev, "%s: invalid clock output count\n", np->name);
>> +		return -EINVAL;
>> +	}
>> +
>> +	clk_data = devm_kmalloc(dev, sizeof(*clk_data), GFP_KERNEL);
>> +	if (!clk_data)
>> +		return -ENOMEM;
>> +
>> +	clks = devm_kcalloc(dev, count, sizeof(*clks), GFP_KERNEL);
>> +	if (!clks)
>> +		return -ENOMEM;
>> +
>> +	for (idx = 0; idx < count; idx++) {
>> +		struct scpi_clk *sclk;
>> +		u32 val;
>> +
>> +		sclk = devm_kzalloc(dev, sizeof(*sclk), GFP_KERNEL);
>> +		if (!sclk)
>> +			return -ENOMEM;
>> +
>> +		if (of_property_read_string_index(np, "clock-output-names",
>> +						  idx, &sclk->name)) {
>> +			dev_err(dev, "invalid clock name @ %s\n", np->name);
>> +			return -EINVAL;
>> +		}
>> +
>> +		if (of_property_read_u32_index(np, "clock-indices",
>> +					       idx, &val)) {
>> +			dev_err(dev, "invalid clock index @ %s\n", np->name);
>> +			return -EINVAL;
>> +		}
>> +
>> +		sclk->id = val;
>> +
>> +		clks[idx] = scpi_clk_ops_init(dev, np, sclk);
>> +		if (IS_ERR_OR_NULL(clks[idx]))
>> +			dev_err(dev, "failed to register clock '%s'\n",
>> +				sclk->name);
>> +		else
>> +			dev_dbg(dev, "Registered clock '%s'\n", sclk->name);
>> +	}
>> +
>> +	clk_data->clks = clks;
>> +	clk_data->clk_num = idx;
>> +	of_clk_add_provider(np, of_clk_src_onecell_get, clk_data);
>
> And if of_clk_add_provider() fails?
>

Ah, my bad, will fix it.

Regards,
Sudeep
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