linux-kernel - Re: [PATCH] sdhci: Forward EPROBE_DEFER on vmmc and vqmmc regulators

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Message-ID: <5332EDBB.7010105@mm-sol.com>
Date:	Wed, 26 Mar 2014 17:09:47 +0200
From:	Georgi Djakov <gdjakov@...sol.com>
To:	Mike Looijmans <mike.looijmans@...ic.nl>, cjb@...top.org,
	linux-mmc@...r.kernel.org
CC:	linux-kernel@...r.kernel.org, git@...inx.com
Subject: Re: [PATCH] sdhci: Forward EPROBE_DEFER on vmmc and vqmmc regulators

On 03/07/2014 04:18 PM, Mike Looijmans wrote:
> If vmmc or vqmmc regulators are controlled by an I2C device, the
> request for the regulator is likely to fail because the I2C bus has
> not been probed yet. The sdhci then incorrectly assumes that the user
> never wanted to use a regulator anyway and continues without ever
> enabling or configuring the required regulator.
>
> To solve this, when a required voltage regulator returns
> EPROBE_DEFER, signalling that the regulator exists but is not
> available yet, forward this error to the probe method instead
> of simply assuming that the user never wanted to use a regulator
> anyway.
>
> Tested on a custom board that has an I2C regulator for one of the sdhcis
> and no regulators at all for the other. This patch enables such a system
> to work correctly.
> ---
>   drivers/mmc/host/sdhci.c |    8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 34aef81..43b90c1 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2972,6 +2972,8 @@ int sdhci_add_host(struct sdhci_host *host)
>   	host->vqmmc = regulator_get_optional(mmc_dev(mmc), "vqmmc");
>   	if (IS_ERR_OR_NULL(host->vqmmc)) {
>   		if (PTR_ERR(host->vqmmc) < 0) {
> +			if (PTR_ERR(host->vqmmc) == -EPROBE_DEFER)
> +				return -EPROBE_DEFER;
>   			pr_info("%s: no vqmmc regulator found\n",
>   				mmc_hostname(mmc));
>   			host->vqmmc = NULL;
> @@ -3048,8 +3050,10 @@ int sdhci_add_host(struct sdhci_host *host)
>   	host->vmmc = regulator_get_optional(mmc_dev(mmc), "vmmc");
>   	if (IS_ERR_OR_NULL(host->vmmc)) {
>   		if (PTR_ERR(host->vmmc) < 0) {
> -			pr_info("%s: no vmmc regulator found\n",
> -				mmc_hostname(mmc));
> +			if (PTR_ERR(host->vmmc) == -EPROBE_DEFER)
> +				return -EPROBE_DEFER;
> +			pr_info("%s: no vmmc regulator found (%d)\n",

I suggest using %ld here. The rest looks fine to me! Thanks!

> +				mmc_hostname(mmc), PTR_ERR(host->vmmc));
>   			host->vmmc = NULL;
>   		}
>   	}
>

BR,
Georgi

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