Re: [PATCH V2] mmc: sdhci-msm: Don't enable PWRSAVE_DLL for certain sdhc hosts

[Adrian Hunter]

On 7/02/20 2:04 pm, Veerabhadrarao Badiganti wrote:
> From: Ritesh Harjani <riteshh@xxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxx>
> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@xxxxxxxxxxxxxx>

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

> --
> 
> 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
>