linux-kernel - Re: [PATCH v2 07/34] media: iris: initialize power resources

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Date: Wed, 3 Jan 2024 14:45:17 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dikshita Agarwal <quic_dikshita@...cinc.com>,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 stanimir.k.varbanov@...il.com, quic_vgarodia@...cinc.com, agross@...nel.org,
 andersson@...nel.org, mchehab@...nel.org, bryan.odonoghue@...aro.org
Cc: linux-arm-msm@...r.kernel.org, quic_abhinavk@...cinc.com
Subject: Re: [PATCH v2 07/34] media: iris: initialize power resources

On 20.12.2023 09:04, Dikshita Agarwal wrote:
> 
> 
> On 12/18/2023 8:39 PM, Konrad Dybcio wrote:
>> On 18.12.2023 12:32, Dikshita Agarwal wrote:
>>> Add support for initializing Iris "resources", which are clocks,
>>> interconnects, power domains, reset clocks, and clock frequencies
>>> used for Iris hardware.
>>>
>>> Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
>>> ---
[...]

>>> +
>>> +	for (i = 0; i < core->clk_count; i++) {
>>> +		cinfo = &core->clock_tbl[i];
>>> +		cinfo->name = plat_clk_table[i].name;
>>> +		cinfo->clk_id = plat_clk_table[i].clk_id;
>>> +		cinfo->has_scaling = plat_clk_table[i].has_scaling;
>>> +		cinfo->clk = devm_clk_get(core->dev, cinfo->name);
>>> +		if (IS_ERR(cinfo->clk)) {
>>> +			dev_err(core->dev,
>>> +				"%s: failed to get clock: %s\n", __func__, cinfo->name);
>>> +			return PTR_ERR(cinfo->clk);
>>> +		}
>>> +	}
>> Are you not going to use OPP for scaling the main RPMhPD with the core
>> clock?
>>
> We are using OPP for scaling the vcodec clk.
> Could you please elaborate you query here, may be I didn't understand fully.

It's just that this approach of scanning everything we know and
expect about the clock seems a bit unnecessary.. Going with the
approach I suggested below (i.e. separate struct clk for important
ones like core or mem clock) simplify this to the point where you
just set opp_set_rate on the imporant ones and you can throw
clk_bulk_ operations at the ones that simply need to be en/disabled.

Konrad

[...]

>>> +
>>> +struct power_domain_info {
>>> +	struct device	*genpd_dev;
>>> +	const char	*name;
>>> +};
>>> +
>>> +struct clock_info {
>>> +	struct clk	*clk;
>>> +	const char	*name;
>> I'm not sure why you need it
>>
>>> +	u32		clk_id;
>> Or this
>>
>>> +	bool		has_scaling;
>> Or this
>>
>> you could probably do something like this:
>>
>> struct big_iris_struct {
>> 	[...]
>> 	struct clk *core_clk;
>> 	struct clk *memory_clk;
>> 	struct clk *some_important_scaled_clock;
>> 	struct clk_bulk_data less_important_nonscaling_clocks[X]
>> }
>>
>> and then make use of all of the great common upstream APIs to manage
>> them!
>>
> Will explore this and get back.