linux-kernel - Re: [PATCH] MMC/omap_hsmmc: handle failure of regulator

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Date:	Mon, 30 Jul 2012 16:48:10 +1000
From:	NeilBrown <neilb@...e.de>
To:	Rajendra Nayak <rnayak@...com>
Cc:	Chris Ball <cjb@...top.org>, Venkatraman S <svenkatr@...com>,
	Balaji T K <balajitk@...com>, linux-omap@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MMC/omap_hsmmc: handle failure of regulator_get better.

On Mon, 30 Jul 2012 12:07:09 +0530 Rajendra Nayak <rnayak@...com> wrote:

> On Monday 30 July 2012 11:54 AM, NeilBrown wrote:
> > On Mon, 30 Jul 2012 10:50:36 +0530 Rajendra Nayak<rnayak@...com>  wrote:
> >
> >> On Monday 30 July 2012 05:42 AM, NeilBrown wrote:
> >>>
> >>> 1/ if regulator_get fails, return an error.  This is important
> >>>      if it failed with EPROBE_DEFER, as the probe needs to be
> >>>      deferred.
> >>>
> >>> 2/ Don't set .set_power until the regulator has been found, or
> >>>      the deferred probe will not bother calling omap_hsmmc_reg_get().
> >>
> >> I am not very sure, but aren't the data structures re-allocated on a
> >> re-probe (after it was deferred) causing .set_power to be lost anyway?
> >>
> >
> > Apparently not - as I needed to make that change before the re-probe would
> > work.
> >
> > Looking at the code to remind myself:
> >
> > #define mmc_slot(host)		(host->pdata->slots[host->slot_id])
> >
> > so the slot is inside the platform data which is allocated in
> > omap_hsmmc_init_one, called from omap_hsmmc_init.
> > This is all prior to the probing of the device.
> >
> > So no: once set_power is set, it stays set.
> 
> Thanks for the explanation, makes sense.
> 
> Acked-by: Rajendra Nayak <rnayak@...com>

Thanks.

> 
> Btw, is the support for re-probe/deferred probe already merged
> now? or are you testing this with some out of tree patches.

deferred-probe works in 3.5. 

commit 04bf30115f4ba2beda1efb6cfbae49cdc757f3a9
Author: Mark Brown <broonie@...nsource.wolfsonmicro.com>
Date:   Sun Mar 11 13:07:56 2012 +0000

    regulator: Support driver probe deferral
 
makes it work for regulators.

commit d1c3414c2a9d10ef7f0f7665f5d2947cd088c093
Author: Grant Likely <grant.likely@...retlab.ca>
Date:   Mon Mar 5 08:47:41 2012 -0700

    drivercore: Add driver probe deferral mechanism

added the basic mechanism.

GPIOs are also supported in 3.6-rc thanks to

commit e93545763021988def06fbda28fe5da133589a96
Author: Mark Brown <broonie@...nsource.wolfsonmicro.com>
Date:   Mon Jul 9 12:22:56 2012 +0100

    gpiolib: Defer failed gpio requests by default

so the omap_hsmmc_late_init() stuff can probably be removed, though I haven't
tried and there might be some subtlety in there that isn't covered by
EPROBE_DEFER

NeilBrown


> 
> >
> > Thanks,
> > NeilBrown
> >
> >>>
> >>> Signed-off-by: NeilBrown<neilb@...e.de>
> >>>
> >>> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> >>> index 389a3ee..f052c29 100644
> >>> --- a/drivers/mmc/host/omap_hsmmc.c
> >>> +++ b/drivers/mmc/host/omap_hsmmc.c
> >>> @@ -299,12 +299,12 @@ static int omap_hsmmc_reg_get(struct omap_hsmmc_host *host)
> >>>    	struct regulator *reg;
> >>>    	int ocr_value = 0;
> >>>
> >>> -	mmc_slot(host).set_power = omap_hsmmc_set_power;
> >>> -
> >>>    	reg = regulator_get(host->dev, "vmmc");
> >>>    	if (IS_ERR(reg)) {
> >>>    		dev_dbg(host->dev, "vmmc regulator missing\n");
> >>> +		return PTR_ERR(reg);
> >>>    	} else {
> >>> +		mmc_slot(host).set_power = omap_hsmmc_set_power;
> >>>    		host->vcc = reg;
> >>>    		ocr_value = mmc_regulator_get_ocrmask(reg);
> >>>    		if (!mmc_slot(host).ocr_mask) {
> >


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