linux-kernel - Re: [PATCH 1/3] mmc: sdhci-sprd: Add start_signal_voltage

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Date:   Mon, 1 Jul 2019 16:31:18 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Baolin Wang <baolin.wang@...aro.org>, ulf.hansson@...aro.org,
        zhang.lyra@...il.com, orsonzhai@...il.com, robh+dt@...nel.org,
        mark.rutland@....com
Cc:     vincent.guittot@...aro.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] mmc: sdhci-sprd: Add start_signal_voltage_switch ops

On 21/06/19 9:12 AM, Baolin Wang wrote:
> For Spreadtrum SD host controller, we can not use standard SD registers
> to change and detect the I/O voltage signals, since our voltage regulator
> for I/O is fixed in hardware, and no signals were connected to the SD
> controller. Thus add Spreadtrum specific voltage switch ops to change
> voltage instead of using standard SD host registers.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>

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

> ---
>  drivers/mmc/host/sdhci-sprd.c |   24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
> index 024c3c5..8b23c88 100644
> --- a/drivers/mmc/host/sdhci-sprd.c
> +++ b/drivers/mmc/host/sdhci-sprd.c
> @@ -403,6 +403,22 @@ static void sdhci_sprd_request(struct mmc_host *mmc, struct mmc_request *mrq)
>  	sdhci_request(mmc, mrq);
>  }
>  
> +static int sdhci_sprd_voltage_switch(struct mmc_host *mmc, struct mmc_ios *ios)
> +{
> +	int ret;
> +
> +	if (!IS_ERR(mmc->supply.vqmmc)) {
> +		ret = mmc_regulator_set_vqmmc(mmc, ios);
> +		if (ret) {
> +			pr_err("%s: Switching signalling voltage failed\n",
> +			       mmc_hostname(mmc));
> +			return ret;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static void sdhci_sprd_hs400_enhanced_strobe(struct mmc_host *mmc,
>  					     struct mmc_ios *ios)
>  {
> @@ -470,6 +486,14 @@ static int sdhci_sprd_probe(struct platform_device *pdev)
>  	host->mmc_host_ops.request = sdhci_sprd_request;
>  	host->mmc_host_ops.hs400_enhanced_strobe =
>  		sdhci_sprd_hs400_enhanced_strobe;
> +	/*
> +	 * We can not use the standard ops to change and detect the voltage
> +	 * signal for Spreadtrum SD host controller, since our voltage regulator
> +	 * for I/O is fixed in hardware, that means we do not need control
> +	 * the standard SD host controller to change the I/O voltage.
> +	 */
> +	host->mmc_host_ops.start_signal_voltage_switch =
> +		sdhci_sprd_voltage_switch;
>  
>  	host->mmc->caps = MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED |
>  		MMC_CAP_ERASE | MMC_CAP_CMD23;
>