linux-kernel - Re: [PATCH v3 12/17] media: venus: core: Add support for opp tables/perf voting

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Date:   Wed, 29 Apr 2020 20:40:42 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        viresh.kumar@...aro.org, sboyd@...nel.org,
        bjorn.andersson@...aro.org, agross@...nel.org
Cc:     linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, mka@...omium.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v3 12/17] media: venus: core: Add support for opp
 tables/perf voting

Hey Stan,

On 4/29/2020 8:06 PM, Stanimir Varbanov wrote:
> Hi Rajendra,
> 
> Thanks for the patch!
> 
[]..

>>   #include <linux/pm_runtime.h>
>>   #include <media/videobuf2-v4l2.h>
>>   #include <media/v4l2-mem2mem.h>
>> @@ -214,6 +215,20 @@ static int venus_probe(struct platform_device *pdev)
>>   	if (!core->pm_ops)
>>   		return -ENODEV;
>>   
>> +	core->opp_table = dev_pm_opp_set_clkname(dev, "core");
> 
> Should we set opp clkname if opp_of_add_table fails? We have platforms
> which don't have opp tables in Venus DT node. We have to be backward
> compatible for them.

so the way its designed, you are expected to call dev_pm_opp_set_clkname()
*before* adding any OPPs from the OPP table.
As for backward compatibility its already handled by the OPP core now [1]
which makes sure dev_pm_opp_set_rate() is equivalent to a clk_set_rate()
in case of a missing OPP table.

>> +	if (IS_ERR(core->opp_table))
>> +		return PTR_ERR(core->opp_table);
>> +
>> +	if (core->res->opp_pmdomain) {
>> +		ret = dev_pm_opp_of_add_table(dev);
>> +		if (!ret) {
>> +			core->has_opp_table = true;
>> +		} else if (ret != -ENODEV) {
> 
> Is it possible dev_pm_opp_of_add_table() to return EPROBE_DEFER?

Nope, it does not, I had checked.

>> +			dev_err(dev, "Invalid OPP table in Device tree\n");
> 
> ... if so, please drop dev_err.
> 
>> +			return ret;
>> +		}
>> +	}
[]..

>> --- a/drivers/media/platform/qcom/venus/pm_helpers.c
>> +++ b/drivers/media/platform/qcom/venus/pm_helpers.c
>> @@ -9,6 +9,7 @@
>>   #include <linux/iopoll.h>
>>   #include <linux/kernel.h>
>>   #include <linux/pm_domain.h>
>> +#include <linux/pm_opp.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/types.h>
>>   #include <media/v4l2-mem2mem.h>
>> @@ -66,10 +67,9 @@ static void core_clks_disable(struct venus_core *core)
>>   
>>   static int core_clks_set_rate(struct venus_core *core, unsigned long freq)
>>   {
>> -	struct clk *clk = core->clks[0];
>>   	int ret;
>>   
>> -	ret = clk_set_rate(clk, freq);
>> +	ret = dev_pm_opp_set_rate(core->dev, freq);
> 
> Is this will work for legacy platforms without OPP tables?

yes, see [1] which is already merged in mainline.

> 
> Also what about the other clocks (vicodec0,1) in this function.

We continue to use clk_set_rate() for those. The performance state
is associated with only the core clk.

>>   	if (ret)
>>   		return ret;
>>   
>> @@ -740,13 +740,15 @@ static int venc_power_v4(struct device *dev, int on)
>>   
>>   static int vcodec_domains_get(struct device *dev)
>>   {
>> +	struct opp_table *opp_table;
>> +	struct device **opp_virt_dev;
>>   	struct venus_core *core = dev_get_drvdata(dev);
>>   	const struct venus_resources *res = core->res;
>>   	struct device *pd;
>>   	unsigned int i;
>>   
>>   	if (!res->vcodec_pmdomains_num)
>> -		return -ENODEV;
>> +		goto skip_pmdomains;
>>   
>>   	for (i = 0; i < res->vcodec_pmdomains_num; i++) {
>>   		pd = dev_pm_domain_attach_by_name(dev,
>> @@ -763,6 +765,24 @@ static int vcodec_domains_get(struct device *dev)
>>   	if (!core->pd_dl_venus)
>>   		return -ENODEV;
>>   
>> +skip_pmdomains:
>> +	if (!res->opp_pmdomain || !core->has_opp_table)
>> +		return 0;
>> +
>> +	/* Attach the power domain for setting performance state */
>> +	opp_table = dev_pm_opp_attach_genpd(dev, res->opp_pmdomain, &opp_virt_dev);
>> +	if (IS_ERR(opp_table)) {
>> +		return PTR_ERR(opp_table);
>> +	} else if (opp_virt_dev) {
>> +		core->opp_pmdomain = *opp_virt_dev;
>> +		core->opp_dl_venus = device_link_add(dev, core->opp_pmdomain,
>> +						     DL_FLAG_RPM_ACTIVE |
>> +						     DL_FLAG_PM_RUNTIME |
>> +						     DL_FLAG_STATELESS);
>> +		if (!core->opp_dl_venus)
>> +			return -ENODEV;
> 
> I think as you return ENODEV you have to detach opp domain here because
> vcodec_domains_put() is not called in error path.

Ok, I'll fix that up.

Thanks for the review.

[1] https://lkml.org/lkml/2020/4/8/413

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