linux-kernel - Re: [PATCH v1] cpufreq: tegra20: Fix imbalanced clock enable count

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Date:   Wed, 23 May 2018 17:46:25 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] cpufreq: tegra20: Fix imbalanced clock enable count

On 23.05.2018 13:44, Dmitry Osipenko wrote:
> On 23.05.2018 08:58, Viresh Kumar wrote:
>> On 23-05-18, 00:14, Dmitry Osipenko wrote:
>>> Tegra20-cpufreq driver missed enabling the CPU clocks. This results in a
>>> clock-enable refcount disbalance on PLL_P <-> PLL_X reparent, causing
>>> PLL_X to get disabled while it shouldn't. Fix this by enabling the clocks
>>> on the driver probe.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>
>>> CPUFreq maintainers,
>>>
>>> Please take into account that this patch is made on top of my recent
>>> series of patches [0] "Clean up Tegra20 cpufreq driver" that was fully
>>> reviewed, but seems not applied yet. Let me know if you prefer to re-spin
>>> the [0], including this patch into the series.
>>>
>>> [0] https://patchwork.ozlabs.org/project/linux-tegra/list/?series=45321
>>
>> This is already picked by Rafael and is sitting in pm/bleeding-edge
>> branch. Should get merged into linux-next in a day or two.
>>
>>>  drivers/cpufreq/tegra20-cpufreq.c | 16 +++++++++++++++-
>>>  1 file changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/cpufreq/tegra20-cpufreq.c b/drivers/cpufreq/tegra20-cpufreq.c
>>> index 05f57dcd5215..ca5229265b60 100644
>>> --- a/drivers/cpufreq/tegra20-cpufreq.c
>>> +++ b/drivers/cpufreq/tegra20-cpufreq.c
>>> @@ -176,6 +176,14 @@ static int tegra20_cpufreq_probe(struct platform_device *pdev)
>>>  		goto put_pll_x;
>>>  	}
>>>  
>>> +	err = clk_prepare_enable(cpufreq->pll_x_clk);
>>> +	if (err)
>>> +		goto put_pll_p;
>>> +
>>> +	err = clk_prepare_enable(cpufreq->pll_p_clk);
>>> +	if (err)
>>> +		goto disable_pll_x;
>>> +
>>>  	cpufreq->dev = &pdev->dev;
>>>  	cpufreq->driver.get = cpufreq_generic_get;
>>>  	cpufreq->driver.attr = cpufreq_generic_attr;
>>> @@ -192,12 +200,16 @@ static int tegra20_cpufreq_probe(struct platform_device *pdev)
>>>  
>>>  	err = cpufreq_register_driver(&cpufreq->driver);
>>>  	if (err)
>>> -		goto put_pll_p;
>>> +		goto disable_pll_p;
>>>  
>>>  	platform_set_drvdata(pdev, cpufreq);
>>>  
>>>  	return 0;
>>>  
>>> +disable_pll_p:
>>> +	clk_disable_unprepare(cpufreq->pll_p_clk);
>>> +disable_pll_x:
>>> +	clk_disable_unprepare(cpufreq->pll_x_clk);
>>>  put_pll_p:
>>>  	clk_put(cpufreq->pll_p_clk);
>>>  put_pll_x:
>>> @@ -214,6 +226,8 @@ static int tegra20_cpufreq_remove(struct platform_device *pdev)
>>>  
>>>  	cpufreq_unregister_driver(&cpufreq->driver);
>>>  
>>> +	clk_disable_unprepare(cpufreq->pll_p_clk);
>>> +	clk_disable_unprepare(cpufreq->pll_x_clk);
>>>  	clk_put(cpufreq->pll_p_clk);
>>>  	clk_put(cpufreq->pll_x_clk);
>>>  	clk_put(cpufreq->cpu_clk);
>>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>>
> 
> Please hold on this patch, seems I interpreted the cpufreq driver logic
> incorrectly and it is probably fine as it is. I'll re-check later today.
> 

I've re-checked the driver and it is fine, PLL_X disabling is expected on a
switching parent clock to PLL_P as for the target frequency. This patch isn't
needed, please scratch it.

It occurred to me that the driver could be improved further a tad while I was
performing the re-check, hence likely there will be couple more patches from me.