Re: [PATCH v3] mmc: sdhci-pci-gli: fix LPM negotiation so x86/S0ix SoCs can suspend

[Adrian Hunter <adrian.hunter@intel.com>]

On 31/08/23 19:00, 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
> which commonly use S0ix as the suspend mechanism - for example, Intel
> Alder Lake and Raptor Lake processors.
> 
> Failure description:
> 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>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
> 
> Changes in v3:
> - applied maintainer feedback from https://lore.kernel.org/lkml/CACT4zj-BaX4tHji8B8gS5jiKkd-2BcwfzHM4fS-OUn0f8DSxcw@mail.gmail.com/T/#m7cea7b6b987d1ab1ca95feedf2c6f9da5783da5c
> 
> Changes in v2:
> - improved symmetry and error path in s2idle suspend callback (internal review)
> 
>  drivers/mmc/host/sdhci-pci-gli.c | 104 ++++++++++++++++++++-----------
>  1 file changed, 66 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
> index 1792665c9494a..a4ccb6c3e27a6 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 +993,70 @@ 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.
> +	 */
> +	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-
> +	 * 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);
> +
> +	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 +1141,8 @@ 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,