Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932398AbdIHNU1 (ORCPT ); Fri, 8 Sep 2017 09:20:27 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34372 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756283AbdIHNUX (ORCPT ); Fri, 8 Sep 2017 09:20:23 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Baluta , Akinobu Mita , Jonathan Cameron Subject: [PATCH 4.13 17/47] iio: adc: ti-ads1015: add adequate wait time to get correct conversion Date: Fri, 8 Sep 2017 15:18:49 +0200 Message-Id: <20170908131824.319112131@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170908131823.546721606@linuxfoundation.org> References: <20170908131823.546721606@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2703 Lines: 78 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Akinobu Mita commit 4744d4e2afebf9644a439da9ca73d822fdd67bd9 upstream. This driver assumes that the device is operating in the continuous conversion mode which performs the conversion continuously. So this driver inserts a wait time before reading the conversion register if the configuration is changed from a previous request. Currently, the wait time is only the period required for a single conversion that is calculated as the reciprocal of the sampling frequency. However we also need to wait for the the previous conversion to complete. Otherwise we probably get the conversion result for the previous configuration when the sampling frequency is lower. Cc: Daniel Baluta Signed-off-by: Akinobu Mita Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/adc/ti-ads1015.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) --- a/drivers/iio/adc/ti-ads1015.c +++ b/drivers/iio/adc/ti-ads1015.c @@ -242,27 +242,34 @@ static int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val) { int ret, pga, dr, conv_time; - bool change; + unsigned int old, mask, cfg; if (chan < 0 || chan >= ADS1015_CHANNELS) return -EINVAL; + ret = regmap_read(data->regmap, ADS1015_CFG_REG, &old); + if (ret) + return ret; + pga = data->channel_data[chan].pga; dr = data->channel_data[chan].data_rate; + mask = ADS1015_CFG_MUX_MASK | ADS1015_CFG_PGA_MASK | + ADS1015_CFG_DR_MASK; + cfg = chan << ADS1015_CFG_MUX_SHIFT | pga << ADS1015_CFG_PGA_SHIFT | + dr << ADS1015_CFG_DR_SHIFT; - ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG, - ADS1015_CFG_MUX_MASK | - ADS1015_CFG_PGA_MASK | - ADS1015_CFG_DR_MASK, - chan << ADS1015_CFG_MUX_SHIFT | - pga << ADS1015_CFG_PGA_SHIFT | - dr << ADS1015_CFG_DR_SHIFT, - &change); - if (ret < 0) + cfg = (old & ~mask) | (cfg & mask); + + ret = regmap_write(data->regmap, ADS1015_CFG_REG, cfg); + if (ret) return ret; - if (change || data->conv_invalid) { - conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]); + if (old != cfg || data->conv_invalid) { + int dr_old = (old & ADS1015_CFG_DR_MASK) >> + ADS1015_CFG_DR_SHIFT; + + conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]); + conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]); usleep_range(conv_time, conv_time + 1); data->conv_invalid = false; }