linux-kernel - regulator: tps6586x: What is the meaning of TPS6586X_SLEW_RATE

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Date:	Tue, 19 Jun 2012 19:15:22 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Mike Rapoport <mike@...pulab.co.il>,
	Danny Huang <dahuang@...dia.com>, Liam Girdwood <lrg@...com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: regulator: tps6586x: What is the meaning of TPS6586X_SLEW_RATE_SET
 setting?

Hi Mike,
While looking at the datasheet (tps65860 and tps65862),
I don't understand why we have TPS6586X_SLEW_RATE_SET (0x08) in the code.

According to the datasheet, BIT3 of SM1SL/SM0SL is not used:

SM1SL [Addr 0x25]
SM0SL [Addr 0x28]
        BIT[2:0] SM0/SM1 SUPPLY RAMP RATE
        BIT[7:3] NOT USED

So why we need to check the "unused bit" in tps6586x_regulator_set_slew_rate()?

        if (!(setting->slew_rate & TPS6586X_SLEW_RATE_SET))
                return 0;

Regards,
Axel

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