linux-kernel - Re: [PATCH v2] mmc: sdhci-pci-gli: Disable LPM during initialization

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Date:   Mon, 20 Nov 2023 15:33:42 +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 v2] mmc: sdhci-pci-gli: Disable LPM during initialization

On 14/11/23 13:54, 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>

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

> ---
> v2: Move up gl9763e_set_low_power_negotiation to avoid having to forward
>     declare it.
> 
>  drivers/mmc/host/sdhci-pci-gli.c | 54 +++++++++++++++++---------------
>  1 file changed, 29 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
> index d8a991b349a8..77911a57b12c 100644
> --- a/drivers/mmc/host/sdhci-pci-gli.c
> +++ b/drivers/mmc/host/sdhci-pci-gli.c
> @@ -1189,6 +1189,32 @@ static void gl9763e_hs400_enhanced_strobe(struct mmc_host *mmc,
>  	sdhci_writel(host, val, SDHCI_GLI_9763E_HS400_ES_REG);
>  }
>  
> +static void gl9763e_set_low_power_negotiation(struct sdhci_pci_slot *slot,
> +					      bool enable)
> +{
> +	struct pci_dev *pdev = slot->chip->pdev;
> +	u32 value;
> +
> +	pci_read_config_dword(pdev, PCIE_GLI_9763E_VHS, &value);
> +	value &= ~GLI_9763E_VHS_REV;
> +	value |= FIELD_PREP(GLI_9763E_VHS_REV, GLI_9763E_VHS_REV_W);
> +	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
> +
> +	pci_read_config_dword(pdev, PCIE_GLI_9763E_CFG, &value);
> +
> +	if (enable)
> +		value &= ~GLI_9763E_CFG_LPSN_DIS;
> +	else
> +		value |= GLI_9763E_CFG_LPSN_DIS;
> +
> +	pci_write_config_dword(pdev, PCIE_GLI_9763E_CFG, value);
> +
> +	pci_read_config_dword(pdev, PCIE_GLI_9763E_VHS, &value);
> +	value &= ~GLI_9763E_VHS_REV;
> +	value |= FIELD_PREP(GLI_9763E_VHS_REV, GLI_9763E_VHS_REV_R);
> +	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
> +}
> +
>  static void sdhci_set_gl9763e_signaling(struct sdhci_host *host,
>  					unsigned int timing)
>  {
> @@ -1297,6 +1323,9 @@ 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:
> @@ -1340,31 +1369,6 @@ static void gli_set_gl9763e(struct sdhci_pci_slot *slot)
>  }
>  
>  #ifdef CONFIG_PM
> -static void gl9763e_set_low_power_negotiation(struct sdhci_pci_slot *slot, bool enable)
> -{
> -	struct pci_dev *pdev = slot->chip->pdev;
> -	u32 value;
> -
> -	pci_read_config_dword(pdev, PCIE_GLI_9763E_VHS, &value);
> -	value &= ~GLI_9763E_VHS_REV;
> -	value |= FIELD_PREP(GLI_9763E_VHS_REV, GLI_9763E_VHS_REV_W);
> -	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
> -
> -	pci_read_config_dword(pdev, PCIE_GLI_9763E_CFG, &value);
> -
> -	if (enable)
> -		value &= ~GLI_9763E_CFG_LPSN_DIS;
> -	else
> -		value |= GLI_9763E_CFG_LPSN_DIS;
> -
> -	pci_write_config_dword(pdev, PCIE_GLI_9763E_CFG, value);
> -
> -	pci_read_config_dword(pdev, PCIE_GLI_9763E_VHS, &value);
> -	value &= ~GLI_9763E_VHS_REV;
> -	value |= FIELD_PREP(GLI_9763E_VHS_REV, GLI_9763E_VHS_REV_R);
> -	pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
> -}
> -
>  static int gl9763e_runtime_suspend(struct sdhci_pci_chip *chip)
>  {
>  	struct sdhci_pci_slot *slot = chip->slots[0];