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From: Axel Lin <axel.lin@gmail.com>
To: "Zhang, Sonic" <Sonic.Zhang@analog.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	Mark Brown <broonie@opensource.wolfsonmicro.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Liam Girdwood <lrg@ti.com>
Subject: RE: [PATCH v2] regulator: ad5398: Fix min/max current limit boundary checking
Date: Tue, 03 Jul 2012 19:36:13 +0800	[thread overview]
Message-ID: <1341315373.3158.3.camel@phoenix> (raw)
In-Reply-To: <DB904C5425BA6F4E8424B3B51A1414D17140805E4C@NWD2CMBX1.ad.analog.com>


> >The equation to calculate the selector does not depend on max_uA.
> >So I think we don't need to set the requested max_uA.
> >
> 
> But, ad5398_set_current_limit() behaves different for min_uA and max_uA with you patch. Is this expected?
> 

What we want is to set the smallest current supported by this hardware
within the range you requested.

Current code uses below equation to choose selector:
selector = DIV_ROUND_UP((min_uA - chip->min_uA) * chip->current_level,
                        range_uA);

With this equation, we need to ensure min_uA >= chip->min_uA,
otherwise it returns a negative selector.

That is why we need to add:
if (min_uA < chip->min_uA)
        min_uA = chip->min_uA;


Axel


  reply	other threads:[~2012-07-03 11:36 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-03  7:42 [PATCH v2] regulator: ad5398: Fix min/max current limit boundary checking Axel Lin
2012-07-03  7:54 ` Zhang, Sonic
2012-07-03  8:06   ` Lars-Peter Clausen
2012-07-03  8:13     ` Zhang, Sonic
2012-07-03  8:24       ` Lars-Peter Clausen
2012-07-03  8:33         ` Zhang, Sonic
2012-07-03  9:44           ` Axel Lin
2012-07-03  9:51             ` Zhang, Sonic
2012-07-03 11:36               ` Axel Lin [this message]
2012-07-04  2:56                 ` Zhang, Sonic
2012-07-04  3:18                   ` Axel Lin
2012-07-04  3:44                     ` Zhang, Sonic

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