linux-kernel - Re: [PATCH 1/4] mfd: mc13783: Take care of semantic inversion between read and write value of two bits in POWER

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Date:	Sun, 13 Dec 2009 20:56:07 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Alberto Panizzo <maramaopercheseimorto@...il.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Sascha linux-arm <s.hauer@...gutronix.de>,
	linux-arm-kernel-infradead <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] mfd: mc13783: Take care of semantic inversion
	between read and write value of two bits in POWER_MISCELLANEUS
	register.

On Sat, Dec 12, 2009 at 05:48:43PM +0100, Alberto Panizzo wrote:
> MC13783_REGCTRL_PWGTnSPIEN controls the states of the corresponding
> PWGTn_DRV output.
> Reading 1 on the corresponding bit mean that the output is enabled
> Writing 1 on the corresponding bit disable that output!
> 
> So, if not asked directly to modify those bits, write the inverted
> value.
Hmm, I'm not sure this completely right.  The Spec has:

        Bit PWGTxSPIEN | Pin PWGTxEN | PWGTxDRV |  Read Back
          0 = default  |             |          | PWGTxSPIEN
        ---------------+-------------+----------+------------
              1        |      x      |   Low    |     0
              0        |      0      |   High   |     1
              0        |      1      |   Low    |     0

So it looks a bit harder than just inverting the read bit.

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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