From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([178.18.118.26]:57054 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934028AbdC3SWv (ORCPT ); Thu, 30 Mar 2017 14:22:51 -0400 Subject: Re: [RFC/PATCH v3] staging: iio: update locking method during frequency writes To: Gargi Sharma , outreachy-kernel@googlegroups.com References: <1490866426-15575-1-git-send-email-gs051095@gmail.com> Cc: linux-iio@vger.kernel.org, lars@metafoo.de, Michael.Hennerich@analog.com, knaack.h@gmx.de, pmeerw@pmeerw.net, gregkh@linuxfoundation.org From: Jonathan Cameron Message-ID: Date: Thu, 30 Mar 2017 19:22:49 +0100 MIME-Version: 1.0 In-Reply-To: <1490866426-15575-1-git-send-email-gs051095@gmail.com> Content-Type: text/plain; charset=windows-1252 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 30/03/17 10:33, Gargi Sharma wrote: > The driver needs to insure atomicity during frequency > changes of bus and device. The iiodev->mlock as used > was not doing that. Replace it with the drivers existing > buffer lock and introduce an auxiliary spi_write() that does > not hold the lock. > > Signed-off-by: Gargi Sharma Only one comment on this. Why an RFC? I nearly ignored this in my sweep of easy patches to pick up this evening purely because I thought there might still be something that needed real thought in it. It's a clean nice patch that I don't think any substantial questions have been raised against - so just submit it as patch. As an RFC it is underselling itself! Anyhow, never mind, I did look and have applied it ;) Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it. Thanks. Jonathan > --- > Changes in v3: > - Removed unnecessary ret variable inside > __ade7754_spi_write_reg_8 function. > Changes in v2: > - Added auxiliary function. > - Updated the buf_lock comment appropriately. > --- > drivers/staging/iio/meter/ade7754.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/drivers/staging/iio/meter/ade7754.c b/drivers/staging/iio/meter/ade7754.c > index c8d2d4c..91f8740 100644 > --- a/drivers/staging/iio/meter/ade7754.c > +++ b/drivers/staging/iio/meter/ade7754.c > @@ -97,7 +97,7 @@ > /** > * struct ade7754_state - device instance specific data > * @us: actual spi_device > - * @buf_lock: mutex to protect tx and rx > + * @buf_lock: mutex to protect tx, rx and write frequency > * @tx: transmit buffer > * @rx: receive buffer > **/ > @@ -108,17 +108,25 @@ struct ade7754_state { > u8 rx[ADE7754_MAX_RX]; > }; > > -static int ade7754_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val) > +/* Unlocked version of ade7754_spi_write_reg_8 function */ > +static int __ade7754_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val) > { > - int ret; > struct iio_dev *indio_dev = dev_to_iio_dev(dev); > struct ade7754_state *st = iio_priv(indio_dev); > > - mutex_lock(&st->buf_lock); > st->tx[0] = ADE7754_WRITE_REG(reg_address); > st->tx[1] = val; > + return spi_write(st->us, st->tx, 2); > +} > > - ret = spi_write(st->us, st->tx, 2); > +static int ade7754_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val) > +{ > + int ret; > + struct iio_dev *indio_dev = dev_to_iio_dev(dev); > + struct ade7754_state *st = iio_priv(indio_dev); > + > + mutex_lock(&st->buf_lock); > + ret = __ade7754_spi_write_reg_8(dev, reg_address, val); > mutex_unlock(&st->buf_lock); > > return ret; > @@ -513,7 +521,7 @@ static ssize_t ade7754_write_frequency(struct device *dev, > if (!val) > return -EINVAL; > > - mutex_lock(&indio_dev->mlock); > + mutex_lock(&st->buf_lock); > > t = 26000 / val; > if (t > 0) > @@ -531,10 +539,10 @@ static ssize_t ade7754_write_frequency(struct device *dev, > reg &= ~(3 << 3); > reg |= t << 3; > > - ret = ade7754_spi_write_reg_8(dev, ADE7754_WAVMODE, reg); > + ret = __ade7754_spi_write_reg_8(dev, ADE7754_WAVMODE, reg); > > out: > - mutex_unlock(&indio_dev->mlock); > + mutex_unlock(&st->buf_lock); > > return ret ? ret : len; > } >