linux-kernel - Re: [PATCH 2/2] mmc: sdhci-of-at91: set clocks and presets after resume from deepest PM

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Date:   Tue, 20 Jun 2017 10:07:06 +0200
From:   Quentin Schulz <quentin.schulz@...e-electrons.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        ludovic.desroches@...rochip.com, ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        thomas.petazzoni@...e-electrons.com,
        alexandre.belloni@...e-electrons.com, nicolas.ferre@...rochip.com
Subject: Re: [PATCH 2/2] mmc: sdhci-of-at91: set clocks and presets after
 resume from deepest PM

Hi Adrian,

On 20/06/2017 09:39, Adrian Hunter wrote:
> On 16/06/17 10:29, Quentin Schulz wrote:
>> This adds deepest (Backup+Self-Refresh) PM support to the ATMEL SAMA5D2
>> SoC's SDHCI controller.
>>
>> When resuming from deepest state, it is required to restore preset
>> registers as the registers are lost since VDD core has been shut down
>> when entering deepest state on the SAMA5D2. The clocks need to be
>> reconfigured as well.
>>
>> The other registers and init process are taken care of by the SDHCI
>> core.
>>
>> Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com>
>> ---
>>  drivers/mmc/host/sdhci-of-at91.c | 34 ++++++++++++++++++++++++++++++++--
>>  1 file changed, 32 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
>> index fb8c6011f13d..300513fc1068 100644
>> --- a/drivers/mmc/host/sdhci-of-at91.c
>> +++ b/drivers/mmc/host/sdhci-of-at91.c
>> @@ -207,6 +207,37 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
>>  }
>>  
>>  #ifdef CONFIG_PM
> 
> Should be CONFIG_PM_SLEEP for suspend / resume callbacks.
> 

So I let this CONFIG_PM around the runtime_suspend/resume but put
another CONFIG_PM_SLEEP around the suspend/resume functions?

>> +static int sdhci_at91_suspend(struct device *dev)
>> +{
>> +	struct sdhci_host *host = dev_get_drvdata(dev);
>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> +	struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
>> +	int ret;
>> +
>> +	ret = sdhci_suspend_host(host);
>> +
>> +	if (host->runtime_suspended)
>> +		return ret;
> 
> Suspending while runtime suspended seems like a bad idea.  Have you
> considered just adding sdhci_at91_set_clks_presets() to
> sdhci_at91_runtime_resume()?
> 

Adding sdhci_at91_set_clks_presets() to runtime_resume() seems a bad
idea as well. You don't need to recompute the clock rate, set it and set
the presets registers each time you do a runtime_resume. As the
runtime_pm of sdhci has a quite aggressive policy of activation, this
seems like a bad idea on the optimization side.

Thanks,
Quentin

>> +
>> +	clk_disable_unprepare(priv->gck);
>> +	clk_disable_unprepare(priv->hclock);
>> +	clk_disable_unprepare(priv->mainck);
>> +
>> +	return ret;
>> +}
>> +
>> +static int sdhci_at91_resume(struct device *dev)
>> +{
>> +	struct sdhci_host *host = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	ret = sdhci_at91_set_clks_presets(dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return sdhci_resume_host(host);
>> +}
>> +
>>  static int sdhci_at91_runtime_suspend(struct device *dev)
>>  {
>>  	struct sdhci_host *host = dev_get_drvdata(dev);
>> @@ -256,8 +287,7 @@ static int sdhci_at91_runtime_resume(struct device *dev)
>>  #endif /* CONFIG_PM */
>>  
>>  static const struct dev_pm_ops sdhci_at91_dev_pm_ops = {
>> -	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>> -				pm_runtime_force_resume)
>> +	SET_SYSTEM_SLEEP_PM_OPS(sdhci_at91_suspend, sdhci_at91_resume)
>>  	SET_RUNTIME_PM_OPS(sdhci_at91_runtime_suspend,
>>  			   sdhci_at91_runtime_resume,
>>  			   NULL)
>>
> 

-- 
Quentin Schulz, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com