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Date:   Thu, 31 Aug 2023 16:02:16 +0300
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Subject: Re: [PATCH v2] mmc: sdhci-pci-gli: fix LPM negotiation so x86/S0ix
 SoCs can suspend
Content-Language: en-US
From:   Adrian Hunter <adrian.hunter@intel.com>
To:     Sven van Ashbrook <svenva@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>, ulf.hansson@linaro.org
Cc:     jason.lai@genesyslogic.com.tw, skardach@google.com,
        Renius Chen <reniuschengl@gmail.com>,
        linux-mmc@vger.kernel.org, greg.tu@genesyslogic.com.tw,
        jasonlai.genesyslogic@gmail.com, SeanHY.chen@genesyslogic.com.tw,
        ben.chuang@genesyslogic.com.tw, victor.shih@genesyslogic.com.tw,
        stable@vger.kernel.org
References: <20230823174134.v2.1.I7ed1ca09797be2dd76ca914c57d88b32d24dac88@changeid>
 <e22c4a5f-c592-7121-7173-eef669ebdf89@intel.com>
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 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
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On 24/08/23 14:46, Adrian Hunter wrote:
> Hi
> 
> Looks OK - a few minor comments below
> 
> On 23/08/23 20:41, Sven van Ashbrook wrote:
>> To improve the r/w performance of GL9763E, the current driver inhibits LPM
>> negotiation while the device is active.
>>
>> This prevents a large number of SoCs from suspending, notably x86 systems
> 
> If possible, can you give example of which SoCs / products
> 
>> which use S0ix as the suspend mechanism:
>> 1. Userspace initiates s2idle suspend (e.g. via writing to
>>    /sys/power/state)
>> 2. This switches the runtime_pm device state to active, which disables
>>    LPM negotiation, then calls the "regular" suspend callback
>> 3. With LPM negotiation disabled, the bus cannot enter low-power state
>> 4. On a large number of SoCs, if the bus not in a low-power state, S0ix
>>    cannot be entered, which in turn prevents the SoC from entering
>>    suspend.
>>
>> Fix by re-enabling LPM negotiation in the device's suspend callback.
>>
>> Suggested-by: Stanislaw Kardach <skardach@google.com>
>> Fixes: f9e5b33934ce ("mmc: host: Improve I/O read/write performance for GL9763E")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Sven van Ashbrook <svenva@chromium.org>
>>      # on gladios device
>>      # on 15590.0.0 with v5.10 and upstream (v6.4) kernels
>>
> 
> 3 extraneous lines here - please remove
> 
>> ---
>>
>> Changes in v2:
>> - improved symmetry and error path in s2idle suspend callback (internal review)
>>
>>  drivers/mmc/host/sdhci-pci-gli.c | 102 +++++++++++++++++++------------
>>  1 file changed, 64 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
>> index 1792665c9494a..19f577cc8bceb 100644
>> --- a/drivers/mmc/host/sdhci-pci-gli.c
>> +++ b/drivers/mmc/host/sdhci-pci-gli.c
>> @@ -745,42 +745,6 @@ static u32 sdhci_gl9750_readl(struct sdhci_host *host, int reg)
>>  	return value;
>>  }
>>  
>> -#ifdef CONFIG_PM_SLEEP
>> -static int sdhci_pci_gli_resume(struct sdhci_pci_chip *chip)
>> -{
>> -	struct sdhci_pci_slot *slot = chip->slots[0];
>> -
>> -	pci_free_irq_vectors(slot->chip->pdev);
>> -	gli_pcie_enable_msi(slot);
>> -
>> -	return sdhci_pci_resume_host(chip);
>> -}
>> -
>> -static int sdhci_cqhci_gli_resume(struct sdhci_pci_chip *chip)
>> -{
>> -	struct sdhci_pci_slot *slot = chip->slots[0];
>> -	int ret;
>> -
>> -	ret = sdhci_pci_gli_resume(chip);
>> -	if (ret)
>> -		return ret;
>> -
>> -	return cqhci_resume(slot->host->mmc);
>> -}
>> -
>> -static int sdhci_cqhci_gli_suspend(struct sdhci_pci_chip *chip)
>> -{
>> -	struct sdhci_pci_slot *slot = chip->slots[0];
>> -	int ret;
>> -
>> -	ret = cqhci_suspend(slot->host->mmc);
>> -	if (ret)
>> -		return ret;
>> -
>> -	return sdhci_suspend_host(slot->host);
>> -}
>> -#endif
>> -
>>  static void gl9763e_hs400_enhanced_strobe(struct mmc_host *mmc,
>>  					  struct mmc_ios *ios)
>>  {
>> @@ -1029,6 +993,68 @@ static int gl9763e_runtime_resume(struct sdhci_pci_chip *chip)
>>  }
>>  #endif
>>  
>> +#ifdef CONFIG_PM_SLEEP
>> +static int sdhci_pci_gli_resume(struct sdhci_pci_chip *chip)
>> +{
>> +	struct sdhci_pci_slot *slot = chip->slots[0];
>> +
>> +	pci_free_irq_vectors(slot->chip->pdev);
>> +	gli_pcie_enable_msi(slot);
>> +
>> +	return sdhci_pci_resume_host(chip);
>> +}
>> +
>> +static int gl9763e_resume(struct sdhci_pci_chip *chip)
>> +{
>> +	struct sdhci_pci_slot *slot = chip->slots[0];
>> +	int ret;
>> +
>> +	ret = sdhci_pci_gli_resume(chip);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = cqhci_resume(slot->host->mmc);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* Disable LPM negotiation to bring device back in sync
>> +	 * with its runtime_pm state.
>> +	 */
> 
> I would prefer the comment style:
> 
> 	/*
> 	 * Blah, blah ...
> 	 * Blah, blah, blah.
> 	 */
> 
>> +	gl9763e_set_low_power_negotiation(slot, false);
>> +
>> +	return 0;
>> +}
>> +
>> +static int gl9763e_suspend(struct sdhci_pci_chip *chip)
>> +{
>> +	struct sdhci_pci_slot *slot = chip->slots[0];
>> +	int ret;
>> +
>> +	/* Certain SoCs can suspend only with the bus in low-
> 
> Ditto re comment style
> 
>> +	 * power state, notably x86 SoCs when using S0ix.
>> +	 * Re-enable LPM negotiation to allow entering L1 state
>> +	 * and entering system suspend.
>> +	 */
>> +	gl9763e_set_low_power_negotiation(slot, true);
> 
> Couldn't this be at the end of the function, save
> an error path

I think the discussion was a little uncertain over
moving this, so maybe leave it alone.

However please consider my other comments.

> 
>> +
>> +	ret = cqhci_suspend(slot->host->mmc);
>> +	if (ret)
>> +		goto err_suspend;
>> +
>> +	ret = sdhci_suspend_host(slot->host);
>> +	if (ret)
>> +		goto err_suspend_host;
>> +
>> +	return 0;
>> +
>> +err_suspend_host:
>> +	cqhci_resume(slot->host->mmc);
>> +err_suspend:
>> +	gl9763e_set_low_power_negotiation(slot, false);
>> +	return ret;
>> +}
>> +#endif
>> +
>>  static int gli_probe_slot_gl9763e(struct sdhci_pci_slot *slot)
>>  {
>>  	struct pci_dev *pdev = slot->chip->pdev;
>> @@ -1113,8 +1139,8 @@ const struct sdhci_pci_fixes sdhci_gl9763e = {
>>  	.probe_slot	= gli_probe_slot_gl9763e,
>>  	.ops            = &sdhci_gl9763e_ops,
>>  #ifdef CONFIG_PM_SLEEP
>> -	.resume		= sdhci_cqhci_gli_resume,
>> -	.suspend	= sdhci_cqhci_gli_suspend,
>> +	.resume		= gl9763e_resume,
>> +	.suspend	= gl9763e_suspend,
>>  #endif
>>  #ifdef CONFIG_PM
>>  	.runtime_suspend = gl9763e_runtime_suspend,
>