linux-kernel - Re: [PATCH V2] mmc: sdhci-msm: Don't enable PWRSAVE

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Message-ID: <45f9b0d60697571ce2c0e987b3754aa7@codeaurora.org>
Date:   Fri, 07 Feb 2020 20:07:30 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
Cc:     ulf.hansson@...aro.org, adrian.hunter@...el.com,
        asutoshd@...eaurora.org, stummala@...eaurora.org,
        sayalil@...eaurora.org, rampraka@...eaurora.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Ritesh Harjani <riteshh@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH V2] mmc: sdhci-msm: Don't enable PWRSAVE_DLL for certain
 sdhc hosts

On 2020-02-07 20:04, Veerabhadrarao Badiganti wrote:
> From: Ritesh Harjani <riteshh@...eaurora.org>
> 
> SDHC core with new 14lpp and later tech DLL should not enable
> PWRSAVE_DLL since such controller's internal gating cannot meet
> following MCLK requirement:
> When MCLK is gated OFF, it is not gated for less than 0.5us and MCLK
> must be switched on for at-least 1us before DATA starts coming.
> 
> Adding support for this requirement.
> 
> Signed-off-by: Ritesh Harjani <riteshh@...eaurora.org>
> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
> --

Reviewed-by: Can Guo <cang@...eaurora.org>

> 
> Changes since V1:
>   Condition was not correct in V1, which is corrected in V2
> 
> --
> ---
>  drivers/mmc/host/sdhci-msm.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c 
> b/drivers/mmc/host/sdhci-msm.c
> index c3a160c..aa5b610 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -977,9 +977,21 @@ static int
> sdhci_msm_cm_dll_sdc4_calibration(struct sdhci_host *host)
>  		goto out;
>  	}
> 
> -	config = readl_relaxed(host->ioaddr + msm_offset->core_vendor_spec3);
> -	config |= CORE_PWRSAVE_DLL;
> -	writel_relaxed(config, host->ioaddr + msm_offset->core_vendor_spec3);
> +	/*
> +	 * Set CORE_PWRSAVE_DLL bit in CORE_VENDOR_SPEC3.
> +	 * When MCLK is gated OFF, it is not gated for less than 0.5us
> +	 * and MCLK must be switched on for at-least 1us before DATA
> +	 * starts coming. Controllers with 14lpp and later tech DLL cannot
> +	 * guarantee above requirement. So PWRSAVE_DLL should not be
> +	 * turned on for host controllers using this DLL.
> +	 */
> +	if (!msm_host->use_14lpp_dll_reset) {
> +		config = readl_relaxed(host->ioaddr +
> +				msm_offset->core_vendor_spec3);
> +		config |= CORE_PWRSAVE_DLL;
> +		writel_relaxed(config, host->ioaddr +
> +				msm_offset->core_vendor_spec3);
> +	}
> 
>  	/*
>  	 * Drain writebuffer to ensure above DLL calibration