linux-kernel - Re: [PATCH] mmc: sdhci-pci-gli: Disable LPM during initialization

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Message-ID: <fc758174-e286-48f7-bec9-64e4f22bce2f@intel.com>
Date:   Tue, 14 Nov 2023 12:46:57 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Kornel Dulęba <korneld@...omium.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Sven van Ashbrook <svenva@...gle.com>,
        Jason Lai <jasonlai.genesyslogic@...il.com>
Cc:     Victor Shih <victor.shih@...esyslogic.com.tw>,
        Ben Chuang <ben.chuang@...esyslogic.com.tw>,
        Stanisław Kardach <skardach@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mmc: sdhci-pci-gli: Disable LPM during initialization

On 9/11/23 13:19, Kornel Dulęba wrote:
> To address IO performance commit f9e5b33934ce
> ("mmc: host: Improve I/O read/write performance for GL9763E")
> limited LPM negotiation to runtime suspend state.
> The problem is that it only flips the switch in the runtime PM
> resume/suspend logic.
> 
> Disable LPM negotiation in gl9763e_add_host.
> This helps in two ways:
> 1. It was found that the LPM switch stays in the same position after
>    warm reboot. Having it set in init helps with consistency.
> 2. Disabling LPM during the first runtime resume leaves us susceptible
>    to the performance issue in the time window between boot and the
>    first runtime suspend.
> 
> Fixes: f9e5b33934ce ("mmc: host: Improve I/O read/write performance for GL9763E")
> Cc: stable@...r.kernel.org
> Signed-off-by: Kornel Dulęba <korneld@...omium.org>
> ---
>  drivers/mmc/host/sdhci-pci-gli.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
> index d83261e857a5..ce91d1e63a8e 100644
> --- a/drivers/mmc/host/sdhci-pci-gli.c
> +++ b/drivers/mmc/host/sdhci-pci-gli.c
> @@ -220,6 +220,9 @@
>  
>  #define GLI_MAX_TUNING_LOOP 40
>  
> +static void gl9763e_set_low_power_negotiation(struct sdhci_pci_slot *slot,
> +					      bool enable);

Kernel-style is to move the whole function to prevent the need
for forward declaration.

> +
>  /* Genesys Logic chipset */
>  static inline void gl9750_wt_on(struct sdhci_host *host)
>  {
> @@ -1281,6 +1284,9 @@ static int gl9763e_add_host(struct sdhci_pci_slot *slot)
>  	if (ret)
>  		goto cleanup;
>  
> +	/* Disable LPM negotiation to avoid entering L1 state. */
> +	gl9763e_set_low_power_negotiation(slot, false);
> +
>  	return 0;
>  
>  cleanup:
> @@ -1323,7 +1329,6 @@ static void gli_set_gl9763e(struct sdhci_pci_slot *slot)
>  	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
>  }
>  
> -#ifdef CONFIG_PM
>  static void gl9763e_set_low_power_negotiation(struct sdhci_pci_slot *slot, bool enable)
>  {
>  	struct pci_dev *pdev = slot->chip->pdev;
> @@ -1349,6 +1354,7 @@ static void gl9763e_set_low_power_negotiation(struct sdhci_pci_slot *slot, bool
>  	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
>  }
>  
> +#ifdef CONFIG_PM
>  static int gl9763e_runtime_suspend(struct sdhci_pci_chip *chip)
>  {
>  	struct sdhci_pci_slot *slot = chip->slots[0];