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

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Date:	Tue, 23 Oct 2012 15:47:37 +0530
From:	Pavan Kunapuli <pkunapuli@...dia.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>
CC:	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"cjb@...top.org" <cjb@...top.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

For platforms where the board can control vmmc or vqmmc, if the regulator supplies registration is not done before sdhci probe, deferring sdhci probe would ensure that the regulators are available the next time around. For platforms where the board can't control vmmc or vqmmc, we can have a dummy regulator to make sure probe will never get deferred.

-----Original Message-----
From: Jaehoon Chung [mailto:jh80.chung@...sung.com] 
Sent: 23 October 2012 15:41
To: Pavan Kunapuli
Cc: swarren@...dotorg.org; linux@....linux.org.uk; cjb@...top.org; linux-kernel@...r.kernel.org; linux-mmc@...r.kernel.org
Subject: Re: [PATCH 2/2] mmc: sdhci: Defer probe if regulator_get fails

I didn't understand why defer the probe?
I think that some board can't control vqmmc or vmmc.

Best Regards,
Jaehoon Chung
On 10/23/2012 04:18 PM, Pavan Kunapuli wrote:
> vmmc and vqmmc regulators control the voltage to the host and device. 
> Defer the probe if either of them is not registered.
> 
> 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;
>  }
>  
> 

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