linux-kernel - Re: [PATCH v3 02/19] clk: tegra: simplify periph clock data

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Message-ID: <525EC788.9000309@wwwdotorg.org>
Date:	Wed, 16 Oct 2013 11:06:16 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Peter De Schrijver <pdeschrijver@...dia.com>
CC:	Prashant Gaikwad <pgaikwad@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 02/19] clk: tegra: simplify periph clock data

On 10/16/2013 09:06 AM, Peter De Schrijver wrote:
> On Tue, Oct 15, 2013 at 08:46:21PM +0200, Stephen Warren wrote:
>> On 10/15/2013 08:52 AM, Peter De Schrijver wrote:
>>> This patch determines the register bank for clock enable/disable and reset
>>> based on the clock ID instead of hardcoding it in the tables describing the
>>> clocks. This results in less data to be maintained in the tables, making the
>>> code easier to understand. The full benefit of the change will be realized once
>>> also other clocktypes will be table based.
>>
>>> diff --git a/drivers/clk/tegra/clk-tegra114.c b/drivers/clk/tegra/clk-tegra114.c

>>>  	for (i = 0; i < ARRAY_SIZE(tegra_periph_clk_list); i++) {
>>>  		data = &tegra_periph_clk_list[i];
>>> -		clk = tegra_clk_register_periph(data->name, data->parent_names,
>>> -				data->num_parents, &data->periph,
>>> -				clk_base, data->offset, data->flags);
>>> +
>>> +		clk = tegra_clk_register_periph(data->name,
>>> +			data->parent_names, data->num_parents, &data->periph,
>>> +			clk_base, data->offset, data->flags);
>>>  		clks[data->clk_id] = clk;
>>>  	}
>>>  
>>>  	for (i = 0; i < ARRAY_SIZE(tegra_periph_nodiv_clk_list); i++) {
>>>  		data = &tegra_periph_nodiv_clk_list[i];
>>> +
>>>  		clk = tegra_clk_register_periph_nodiv(data->name,
>>
>> Nit: Seems like an unrelated change, and inconsistent with the other
>> loop above.
> 
> Actually it makes it consistent. The previous loop added an empty line
> between data = ... and tegra_clk_register_periph()

Oh right, I see you added the blank line in the chunk about and I'd
overlooked that. I guess it's fine.

>>> diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c
>>
>>> +struct tegra_clk_periph_regs * __init get_reg_bank(int clkid)
>>> +{
>>> +	int reg_bank = clkid / 32;
>>> +
>>> +	if (reg_bank < periph_banks)
>>> +		return &periph_regs[reg_bank];
>>> +	else {
>>> +		WARN_ON(1);
>>> +		return NULL;
>>> +	}
>>> +}
>>> +
>>> +int __init tegra_clk_periph_banks(int num)
>>> +{
>>> +	if (num > ARRAY_SIZE(periph_regs))
>>> +		return -EINVAL;
>>> +
>>> +	periph_banks = num;
>>> +
>>> +	return 0;
>>> +}
>>
>> Shouldn't the condition in tegra_clk_periph_banks() check against
>> periph_banks rather than ARRAY_SIZE(periph_regs)? I assume the calls to
> 
> periph_banks is initialized in tegra_clk_periph_banks(), so I don't see how
> that would work?

Yes, indeed!

>> tegra_clk_periph_banks() from tegra*_clock_init() are intended to ensure
>> that periph_regs is set up correctly in this file? I wonder if
>> s/tegra_clk_periph_banks/tegra_clk_validate_periph_bank_count/ isn't
>> called for?
> 
> Yes. The calls are intended to ensure that the clk-tegra* files, don't
> refer to register banks which don't have addresses specified. This could happen
> if a wrong periph clk ID would be specified for example. In later patches
> we will also allocate memory based on the number of register banks.

Ah, so perhaps s/tegra_clk_periph_banks/tegra_clk_set_periph_banks/
would make it more obvious what it's doing.
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