Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756465AbdIHNdQ (ORCPT ); Fri, 8 Sep 2017 09:33:16 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36590 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933380AbdIHNYB (ORCPT ); Fri, 8 Sep 2017 09:24:01 -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 4.9 11/32] iio: adc: ti-ads1015: avoid getting stale result after runtime resume Date: Fri, 8 Sep 2017 15:19:20 +0200 Message-Id: <20170908131838.131188029@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170908131837.717322849@linuxfoundation.org> References: <20170908131837.717322849@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: 2662 Lines: 83 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Akinobu Mita commit 73e3e3fc50de50cfd68e945d85679c983ed31bd9 upstream. This driver assumes that the device is operating in the continuous conversion mode which performs the conversion continuously. So this driver doesn't insert a wait time before reading the conversion register if the configuration is not changed from a previous request. This assumption is broken if the device is runtime suspended and entered a power-down state. The forthcoming request causes reading a stale result from the conversion register as the device is runtime resumed just before. Fix it by adding a flag to detect that condition and insert a necessary wait time. 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 | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) --- a/drivers/iio/adc/ti-ads1015.c +++ b/drivers/iio/adc/ti-ads1015.c @@ -176,6 +176,12 @@ struct ads1015_data { struct ads1015_channel_data channel_data[ADS1015_CHANNELS]; unsigned int *data_rate; + /* + * Set to true when the ADC is switched to the continuous-conversion + * mode and exits from a power-down state. This flag is used to avoid + * getting the stale result from the conversion register. + */ + bool conv_invalid; }; static bool ads1015_is_writeable_reg(struct device *dev, unsigned int reg) @@ -254,9 +260,10 @@ int ads1015_get_adc_result(struct ads101 if (ret < 0) return ret; - if (change) { + if (change || data->conv_invalid) { conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]); usleep_range(conv_time, conv_time + 1); + data->conv_invalid = false; } return regmap_read(data->regmap, ADS1015_CONV_REG, val); @@ -624,6 +631,8 @@ static int ads1015_probe(struct i2c_clie if (ret) return ret; + data->conv_invalid = true; + ret = pm_runtime_set_active(&client->dev); if (ret) goto err_buffer_cleanup; @@ -679,10 +688,15 @@ static int ads1015_runtime_resume(struct { struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev)); struct ads1015_data *data = iio_priv(indio_dev); + int ret; - return regmap_update_bits(data->regmap, ADS1015_CFG_REG, + ret = regmap_update_bits(data->regmap, ADS1015_CFG_REG, ADS1015_CFG_MOD_MASK, ADS1015_CONTINUOUS << ADS1015_CFG_MOD_SHIFT); + if (!ret) + data->conv_invalid = true; + + return ret; } #endif