From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755878AbcFAQWT (ORCPT ); Wed, 1 Jun 2016 12:22:19 -0400 Received: from www381.your-server.de ([78.46.137.84]:47123 "EHLO www381.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932288AbcFAQWS (ORCPT ); Wed, 1 Jun 2016 12:22:18 -0400 Subject: Re: [PATCH] staging: iio: ad5933: fix handling of settling time cycles To: Luis de Bethencourt , linux-kernel@vger.kernel.org References: <1464796525-9030-1-git-send-email-luisbg@osg.samsung.com> Cc: gregkh@linuxfoundation.org, Michael.Hennerich@analog.com, jic23@kernel.org, knaack.h@gmx.de, pmeerw@pmeerw.net, linux-iio@vger.kernel.org, devel@driverdev.osuosl.org From: Lars-Peter Clausen Message-ID: <574F0BB5.7080105@metafoo.de> Date: Wed, 1 Jun 2016 18:22:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.8.0 MIME-Version: 1.0 In-Reply-To: <1464796525-9030-1-git-send-email-luisbg@osg.samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: lars@metafoo.de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/01/2016 05:55 PM, Luis de Bethencourt wrote: > Correctly handle the settling time cycles value. The else branch was an > impossible condition (> 1022 in the else branch of > 511) and the handling > of the values was dividing by 2 and 4, with a left shift, instead of > multiplying. > > Based on the Table 13 at the bottom of Page 25 of the Data Sheet: > http://www.analog.com/media/en/technical-documentation/data-sheets/AD5933.pdf > > Signed-off-by: Luis de Bethencourt > --- > > Hi, > > I decided to use the hexadecimal values instead of (1 << 10) and (1 << 9), for > briefness, I could resend using those instead if it is prefered. > > I also decided to use multiplications instead of right-shifts for readability. > I could use change that as well. > > Thanks, > Luis > > drivers/staging/iio/impedance-analyzer/ad5933.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c > index 9f43976..3a2cf8f3 100644 > --- a/drivers/staging/iio/impedance-analyzer/ad5933.c > +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c > @@ -444,10 +444,13 @@ static ssize_t ad5933_store(struct device *dev, > st->settling_cycles = val; > > /* 2x, 4x handling, see datasheet */ > - if (val > 511) > - val = (val >> 1) | (1 << 9); > - else if (val > 1022) > - val = (val >> 2) | (3 << 9); > + if (val & 0x400 && val & 0x200) { > + val &= 0x1ff; > + val *= 4; > + } else if (val & 0x200) { > + val &= 0x1ff; > + val *= 2; > + } This does not look correct. D10 and D9 select an additional multiplier of either 1, 2 or 4. So dividing the value before writing it to the register is the right approach in that case. Just flipping the order in which the conditions are evaluated should be sufficient. > > dat = cpu_to_be16(val); > ret = ad5933_i2c_write(st->client, >