linux-kernel - Re: [PATCH 3/3] regulator: tps65090: Make FETs more reliable

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Date:	Tue, 15 Apr 2014 23:52:10 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Anton Vorontsov <anton@...msg.org>,
	Olof Johansson <olof@...om.net>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	ajaykumar.rs@...sung.com, linux-samsung-soc@...r.kernel.org,
	Simon Glass <sjg@...omium.org>,
	Michael Spang <spang@...omium.org>,
	Sean Paul <seanpaul@...omium.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] regulator: tps65090: Make FETs more reliable

On Tue, Apr 15, 2014 at 01:14:36PM -0700, Doug Anderson wrote:

> Mitigate the problem by:
> * Allow setting the overcurrent wait time so devices with this problem
>   can set it to the max.
> * Add retry logic on enables of FETs.

This is two changes, should really be two patches.

> +- ti,overcurrent-wait: This is applicable to FET registers, which have a
> +  poorly defined "overcurrent wait" field.  If this property is present it
> +  should be between 0 - 3.  If this property isn't present we won't touch the
> +  "overcurrent wait" field and we'll leave it to the BIOS/EC to deal with.

I take it this is the raw value to write to the register?

> +static int tps65090_fet_is_enabled(struct regulator_dev *rdev)
> +{
> +	unsigned int control;
> +	unsigned int expected = rdev->desc->enable_mask | BIT(CTRL_PG_BIT);
> +	int ret;
> +
> +	ret = regmap_read(rdev->regmap, rdev->desc->enable_reg, &control);
> +	if (ret != 0)
> +		return ret;
> +
> +	return (control & expected) == expected;
> +}

No need to open code this, regulator_is_enabled_regmap() can check for
any value in a bitfield.

> +static int tps6090_try_enable_fet(struct regulator_dev *rdev)

Why is this called tps6090_try_enable_fet(), looks like a missing 5?

> +	/*
> +	 * Try enabling multiple times until we succeed since sometimes the
> +	 * first try times out.
> +	 */
> +	for (tries = 0; ; tries++) {
> +		ret = tps6090_try_enable_fet(rdev);
> +		if (!ret)
> +			break;
> +		if (ret != -ENOTRECOVERABLE || tries == MAX_FET_ENABLE_TRIES)
> +			goto err;

Make this a do { } while so we don't have the exit condition missing in
the for loop please, it's doing the right thing but it's not as obvious
as it could be.

> +	if (tries) {
> +		dev_warn(&rdev->dev, "reg %#x enable ok after %d tries\n",
> +			 rdev->desc->enable_reg, tries);
> +	}

No need for braces here, and I guess that ought to be retries rather
than tries (though that is pedantry).

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