linux-kernel - Re: [PATCH V1 1/3] mmc: sdhci: Allow platform controlled voltage switching

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Message-ID: <33e12e51-4b96-032f-845f-7910d654018c@intel.com>
Date:   Wed, 25 Jul 2018 14:53:59 +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, evgreen@...omium.org, dianders@...gle.com,
        sayalil@...eaurora.org
Subject: Re: [PATCH V1 1/3] mmc: sdhci: Allow platform controlled voltage
 switching

On 20/07/18 13:46, 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.
> 
> During setup/cleanup of host, check whether regulator enable/disable
> was already done by platform driver.
> 
> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>
> ---
>  drivers/mmc/host/sdhci.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 1c828e0..494a1e2 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -3472,6 +3472,7 @@ int sdhci_setup_host(struct sdhci_host *host)
>  	unsigned int override_timeout_clk;
>  	u32 max_clk;
>  	int ret;
> +	bool enable_vqmmc = false;
>  
>  	WARN_ON(host == NULL);
>  	if (host == NULL)
> @@ -3485,7 +3486,12 @@ 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 (!mmc->supply.vmmc) {
> +		ret = mmc_regulator_get_supply(mmc);
> +		enable_vqmmc  = true;
> +	} else {
> +		ret = 0;
> +	}
>  	if (ret)
>  		return ret;

Why not

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

>  
> @@ -3736,7 +3742,10 @@ 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 (enable_vqmmc)
> +			ret = regulator_enable(mmc->supply.vqmmc);

Please introduce host->vqmmc_enabled = !ret;

> +		else
> +			ret = 0;
>  		if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>  						    1950000))
>  			host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
> @@ -3984,7 +3993,7 @@ int sdhci_setup_host(struct sdhci_host *host)
>  	return 0;
>  
>  unreg:
> -	if (!IS_ERR(mmc->supply.vqmmc))
> +	if (!IS_ERR(mmc->supply.vqmmc) && enable_vqmmc)

And just make this

	if (host->vqmmc_enabled)

>  		regulator_disable(mmc->supply.vqmmc);
>  undma:
>  	if (host->align_buffer)
> @@ -4002,7 +4011,8 @@ void sdhci_cleanup_host(struct sdhci_host *host)
>  {
>  	struct mmc_host *mmc = host->mmc;
>  
> -	if (!IS_ERR(mmc->supply.vqmmc))
> +	if (!IS_ERR(mmc->supply.vqmmc) &&
> +			(regulator_is_enabled(mmc->supply.vqmmc) > 0))

	if (host->vqmmc_enabled)

>  		regulator_disable(mmc->supply.vqmmc);
>  
>  	if (host->align_buffer)
> @@ -4135,7 +4145,8 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
>  
>  	tasklet_kill(&host->finish_tasklet);
>  
> -	if (!IS_ERR(mmc->supply.vqmmc))
> +	if (!IS_ERR(mmc->supply.vqmmc) &&
> +			(regulator_is_enabled(mmc->supply.vqmmc) > 0))

	if (host->vqmmc_enabled)

>  		regulator_disable(mmc->supply.vqmmc);
>  
>  	if (host->align_buffer)
>