Re: [PATCH 1/2] mmc: dw_mmc: Handle late vmmc regulator with EPROBE_DEFER

[Tomasz Figa <tomasz.figa@gmail.com>]

Hi Doug,

On Thursday 06 of June 2013 21:46:45 Doug Anderson wrote:
> It is possible to specify a regulator that should be turned on when
> dw_mmc is probed.  This regulator is optional, though a warning will
> be printed if it's missing.  The fact that the regulator is optional
> means that (at the moment) it's not possible to use a regulator that
> probes _after_ dw_mmc.
> 
> Fix this limitation by adding the ability to make vmmc required.  If a
> vmmc-supply is specified in the device tree we'll assume that vmmc is
> required.

This interesting case makes me think that regulator core should 
differentiate between regulator lookup failure due to no lookup specified 
and due to the regulator specified in lookup being unavailable, returning 
appropriate (different) error codes.

CCing Mark and Liam.

Best regards,
Tomasz

> Signed-off-by: Doug Anderson <dianders@chromium.org>
> ---
>  .../devicetree/bindings/mmc/synopsis-dw-mshc.txt   |  3 +++
>  drivers/mmc/host/dw_mmc.c                          | 22
> ++++++++++++++++++++-- include/linux/mmc/dw_mmc.h                      
>   |  3 +++
>  3 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt index
> 726fd21..b09d2d0 100644
> --- a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> +++ b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> @@ -55,6 +55,9 @@ Optional properties:
> 
>  * broken-cd: as documented in mmc core bindings.
> 
> +* vmmc-supply: The phandle to the regulator to use for vmmc.  If this
> is +  specified we'll defer probe until we can find this regulator. +
>  Aliases:
> 
>  - All the MSHC controller nodes should be represented in the aliases
> node using diff --git a/drivers/mmc/host/dw_mmc.c
> b/drivers/mmc/host/dw_mmc.c index bc3a1bc..d3a0f8a 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1987,8 +1987,17 @@ static int dw_mci_init_slot(struct dw_mci *host,
> unsigned int id)
> 
>  	host->vmmc = devm_regulator_get(mmc_dev(mmc), "vmmc");
>  	if (IS_ERR(host->vmmc)) {
> -		pr_info("%s: no vmmc regulator found\n", 
mmc_hostname(mmc));
> +		ret = PTR_ERR(host->vmmc);
>  		host->vmmc = NULL;
> +
> +		if (host->pdata->vmmc_required) {
> +			if (ret != -EPROBE_DEFER)
> +				pr_err("%s: vmmc required: %d\n",
> +					mmc_hostname(mmc), ret);
> +			goto err_setup_bus;
> +		}
> +		pr_info("%s: no vmmc regulator found %d\n", 
mmc_hostname(mmc),
> +			ret);
>  	} else {
>  		ret = regulator_enable(host->vmmc);
>  		if (ret) {
> @@ -2026,7 +2035,7 @@ static int dw_mci_init_slot(struct dw_mci *host,
> unsigned int id)
> 
>  err_setup_bus:
>  	mmc_free_host(mmc);
> -	return -EINVAL;
> +	return ret;
>  }
> 
>  static void dw_mci_cleanup_slot(struct dw_mci_slot *slot, unsigned int
> id) @@ -2162,6 +2171,13 @@ static struct dw_mci_board
> *dw_mci_parse_dt(struct dw_mci *host) if (of_find_property(np,
> "enable-sdio-wakeup", NULL))
>  		pdata->pm_caps |= MMC_PM_WAKE_SDIO_IRQ;
> 
> +	/*
> +	 * If vmmc is directly specified in the device tree then we'll 
assume
> +	 * it's required and honor EPROBE_DEFER so it can show up late.
> +	 */
> +	if (of_find_property(np, "vmmc-supply", NULL))
> +		pdata->vmmc_required = 1;
> +
>  	return pdata;
>  }
> 
> @@ -2352,6 +2368,8 @@ int dw_mci_probe(struct dw_mci *host)
>  	/* We need at least one slot to succeed */
>  	for (i = 0; i < host->num_slots; i++) {
>  		ret = dw_mci_init_slot(host, i);
> +		if (ret == -EPROBE_DEFER)
> +			goto err_workqueue;
>  		if (ret)
>  			dev_dbg(host->dev, "slot %d init failed\n", i);
>  		else
> diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
> index 198f0fa..e84d288 100644
> --- a/include/linux/mmc/dw_mmc.h
> +++ b/include/linux/mmc/dw_mmc.h
> @@ -244,6 +244,9 @@ struct dw_mci_board {
>  	/* delay in mS before detecting cards after interrupt */
>  	u32 detect_delay_ms;
> 
> +	/* If true then we won't probe until vmmc is available */
> +	bool vmmc_required;
> +
>  	int (*init)(u32 slot_id, irq_handler_t , void *);
>  	int (*get_ro)(u32 slot_id);
>  	int (*get_cd)(u32 slot_id);