linux-kernel - RE: [PATCH 2/2] mmc: sdhci: Defer probe if regulator

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Message-ID: <C79B248886DD134989C8FF6B096A91AB7EC6B8C78B@BGMAIL01.nvidia.com>
Date:	Tue, 23 Oct 2012 13:46:36 +0530
From:	Pavan Kunapuli <pkunapuli@...dia.com>
To:	Lucas Stach <dev@...xeye.de>
CC:	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"cjb@...top.org" <cjb@...top.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Pavan Kunapuli <pkunapuli@...dia.com>
Subject: RE: [PATCH 2/2] mmc: sdhci: Defer probe if regulator_get fails

>> Does this work with boards where we don't have any MMC supplies? Or are we just deferring the probe indefinitely there?
The probe will be deferred indefinitely.

>> For boards that power MMC unconditionally, are we supposed to add dummy regulators to make them work with this patchset?
Yes. We need to add dummy regulators for boards that power MMC unconditionally. I am not sure if there is any other solution other than using deferred probe that would guarantee regulators availability.

-----Original Message-----
From: Lucas Stach [mailto:dev@...xeye.de] 
Sent: 23 October 2012 13:27
To: Pavan Kunapuli
Cc: swarren@...dotorg.org; linux@....linux.org.uk; cjb@...top.org; linux-tegra@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-mmc@...r.kernel.org
Subject: Re: [PATCH 2/2] mmc: sdhci: Defer probe if regulator_get fails

Am Dienstag, den 23.10.2012, 12:49 +0530 schrieb Pavan Kunapuli:
> vmmc and vqmmc regulators control the voltage to the host and device. 
> Defer the probe if either of them is not registered.
> 
Does this work with boards where we don't have any MMC supplies? Or are we just deferring the probe indefinitely there?

For boards that power MMC unconditionally, are we supposed to add dummy regulators to make them work with this patchset?

> Signed-off-by: Pavan Kunapuli <pkunapuli@...dia.com>
> ---
>  drivers/mmc/host/sdhci.c |   25 ++++++++++++++++++++++---
>  1 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 
> 7922adb..925c403 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2844,11 +2844,17 @@ int sdhci_add_host(struct sdhci_host *host)
>  	    !(host->mmc->caps & MMC_CAP_NONREMOVABLE))
>  		mmc->caps |= MMC_CAP_NEEDS_POLL;
>  
> -	/* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
> +	/*
> +	 * If vqmmc regulator and no 1.8V signalling, then there's no UHS.
> +	 * vqmmc regulator should be present. If it's not present,
> +	 * assume the regulator driver registration is not yet done and
> +	 * defer the probe.
> +	 */
>  	host->vqmmc = regulator_get(mmc_dev(mmc), "vqmmc");
>  	if (IS_ERR(host->vqmmc)) {
> -		pr_info("%s: no vqmmc regulator found\n", mmc_hostname(mmc));
> +		pr_err("%s: no vqmmc regulator found\n", mmc_hostname(mmc));
>  		host->vqmmc = NULL;
> +		return -EPROBE_DEFER;
>  	}
>  	else if (regulator_is_supported_voltage(host->vqmmc, 1800000, 1800000))
>  		regulator_enable(host->vqmmc);
> @@ -2903,10 +2909,17 @@ int sdhci_add_host(struct sdhci_host *host)
>  
>  	ocr_avail = 0;
>  
> +	/*
> +	 * vmmc regulator should be present. If it's not present,
> +	 * assume the regulator driver registration is not yet done
> +	 * and defer the probe.
> +	 */
>  	host->vmmc = regulator_get(mmc_dev(mmc), "vmmc");
>  	if (IS_ERR(host->vmmc)) {
> -		pr_info("%s: no vmmc regulator found\n", mmc_hostname(mmc));
> +		pr_err("%s: no vmmc regulator found\n", mmc_hostname(mmc));
>  		host->vmmc = NULL;
> +		ret = -EPROBE_DEFER;
> +		goto vmmc_err;
>  	} else
>  		regulator_enable(host->vmmc);
>  
> @@ -3121,7 +3134,13 @@ reset:
>  untasklet:
>  	tasklet_kill(&host->card_tasklet);
>  	tasklet_kill(&host->finish_tasklet);
> +vmmc_err:
> +	if (host->vqmmc) {
> +		if (regulator_is_enabled(host->vqmmc))
> +			regulator_disable(host->vqmmc);
>  
> +		regulator_put(host->vqmmc);
> +	}
>  	return ret;
>  }
>