linux-kernel - Re: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage switching

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Message-ID: <53c6d61f-47f5-2e4e-8280-6f76f707799e@intel.com>
Date:   Tue, 10 Jul 2018 14:07:18 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Vijay Viswanath <vviswana@...eaurora.org>, ulf.hansson@...aro.org,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        shawn.lin@...k-chips.com, linux-arm-msm@...r.kernel.org,
        georgi.djakov@...aro.org, devicetree@...r.kernel.org,
        asutoshd@...eaurora.org, stummala@...eaurora.org,
        venkatg@...eaurora.org, jeremymc@...hat.com,
        bjorn.andersson@...aro.org, riteshh@...eaurora.org,
        vbadigan@...eaurora.org, dianders@...gle.com,
        sayalil@...eaurora.org
Subject: Re: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage
 switching

On 21/06/18 15:23, Vijay Viswanath wrote:
> Some controllers can have internal mechanism to inform the SW that it
> is ready for voltage switching. For such controllers, changing voltage
> before the HW is ready can result in various issues.
> 
> Add a quirk, which can be used by drivers of such controllers.
> 
> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>
> ---
>  drivers/mmc/host/sdhci.c | 20 +++++++++++++++-----
>  drivers/mmc/host/sdhci.h |  2 ++
>  2 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 1c828e0..f0346d4 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1615,7 +1615,8 @@ void sdhci_set_power_noreg(struct sdhci_host *host, unsigned char mode,
>  void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
>  		     unsigned short vdd)
>  {
> -	if (IS_ERR(host->mmc->supply.vmmc))
> +	if (IS_ERR(host->mmc->supply.vmmc) ||
> +			(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

I think you should provide your own ->set_power() instead of this

>  		sdhci_set_power_noreg(host, mode, vdd);
>  	else
>  		sdhci_set_power_reg(host, mode, vdd);
> @@ -2009,7 +2010,9 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
>  		ctrl &= ~SDHCI_CTRL_VDD_180;
>  		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>  
> -		if (!IS_ERR(mmc->supply.vqmmc)) {
> +		if (!IS_ERR(mmc->supply.vqmmc) &&
> +				!(host->quirks2 &
> +					SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {

And your own ->start_signal_voltage_switch()

>  			ret = mmc_regulator_set_vqmmc(mmc, ios);
>  			if (ret) {
>  				pr_warn("%s: Switching to 3.3V signalling voltage failed\n",
> @@ -2032,7 +2035,8 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
>  	case MMC_SIGNAL_VOLTAGE_180:
>  		if (!(host->flags & SDHCI_SIGNALING_180))
>  			return -EINVAL;
> -		if (!IS_ERR(mmc->supply.vqmmc)) {
> +		if (!IS_ERR(mmc->supply.vqmmc) &&
> +			!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {
>  			ret = mmc_regulator_set_vqmmc(mmc, ios);
>  			if (ret) {
>  				pr_warn("%s: Switching to 1.8V signalling voltage failed\n",
> @@ -3485,7 +3489,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>  	 * the host can take the appropriate action if regulators are not
>  	 * available.
>  	 */
> -	ret = mmc_regulator_get_supply(mmc);
> +	if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

Since we expect mmc_regulator_get_supply() to have been called, this could be:

	if (!mmc->supply.vmmc) {
		ret = mmc_regulator_get_supply(mmc);
		enable_vqmmc = true;
	} else {
		ret = 0;
	}

> +		ret = mmc_regulator_get_supply(mmc);
> +	else
> +		ret = 0;
>  	if (ret)
>  		return ret;
>  
> @@ -3736,7 +3743,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>  
>  	/* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
>  	if (!IS_ERR(mmc->supply.vqmmc)) {
> -		ret = regulator_enable(mmc->supply.vqmmc);
> +		if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

And this could be:

		if (enable_vqmmc)
			ret = regulator_enable(mmc->supply.vqmmc);
		else
			ret = 0;

However, you still need to ensure regulator_disable(mmc->supply.vqmmc) is
only called if regulator_enable() was called.

> +			ret = regulator_enable(mmc->supply.vqmmc);
> +		else
> +			ret = 0;
>  		if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>  						    1950000))
>  			host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 23966f8..3b0c97a 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -450,6 +450,8 @@ struct sdhci_host {
>   * obtainable timeout.
>   */
>  #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUT			(1<<17)
> +/* Regulator voltage changes are being done from platform layer */
> +#define SDHCI_QUIRK2_INTERNAL_PWR_CTL				(1<<18)

So maybe the quirk is not needed.

>  
>  	int irq;		/* Device IRQ */
>  	void __iomem *ioaddr;	/* Mapped address */
>