From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932184AbbBPT0Q (ORCPT ); Mon, 16 Feb 2015 14:26:16 -0500 Received: from ns.pmeerw.net ([84.19.176.92]:54938 "EHLO pmeerw.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753287AbbBPT0N (ORCPT ); Mon, 16 Feb 2015 14:26:13 -0500 Date: Mon, 16 Feb 2015 20:26:11 +0100 (CET) From: Peter Meerwald To: Irina Tirdea cc: Jonathan Cameron , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Srinivas Pandruvada , Adriana Reus Subject: Re: [PATCH 2/2] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler In-Reply-To: <1424110909-16878-3-git-send-email-irina.tirdea@intel.com> Message-ID: References: <1424110909-16878-1-git-send-email-irina.tirdea@intel.com> <1424110909-16878-3-git-send-email-irina.tirdea@intel.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Reading all axis values in one i2c transfer reduces the delays > introduced by the i2c bus. In case i2c block read is not supported, > fallback to reading each axis as a separate word. see comments inline below > Signed-off-by: Adriana Reus > Signed-off-by: Irina Tirdea > Reviewed-by: Srinivas Pandruvada > --- > drivers/iio/accel/kxcjk-1013.c | 44 +++++++++++++++++++++++++++++++++--------- > 1 file changed, 35 insertions(+), 9 deletions(-) > > diff --git a/drivers/iio/accel/kxcjk-1013.c b/drivers/iio/accel/kxcjk-1013.c > index 5f27787..bfa2899 100644 > --- a/drivers/iio/accel/kxcjk-1013.c > +++ b/drivers/iio/accel/kxcjk-1013.c > @@ -109,6 +109,8 @@ struct kxcjk1013_data { > int64_t timestamp; > enum kx_chipset chipset; > bool is_smo8500_device; > + s32 (*read_block_data)(const struct i2c_client *client, u8 command, > + u8 length, u8 *values); probably this could/should be done in the i2c layer or we end up adding a similar function in every driver? > }; > > enum kxcjk1013_axis { > @@ -216,6 +218,23 @@ static const struct { > {800, 0, 0x06}, > {1600, 0, 0x06} }; > > +static s32 kxcjk1013_read_block_data(const struct i2c_client *client, > + u8 command, u8 length, u8 *values) > +{ > + s32 data; > + u8 i; > + > + for (i = 0; i < length; i += 2) { > + data = i2c_smbus_read_word_data(client, command + i); > + if (data < 0) > + return data; > + > + values[i] = data & 0xFF; > + values[i+1] = data >> 8; this is incorrect; it forces the data to be little endian, however, the endianness (as specified in the driver's .scan_type) is IIO_CPU -- the code breaks for big-endian CPUs since _read_i2c_block_data() can't do endianness conversion (and the chip does i2c endianness, i.e. little-endian), the .scan_type should become IIO_LE and above code is correct again but still ugly :) bottom line: change .scan_type to IIO_LE > + } > + return i; > +} > + > static int kxcjk1013_set_mode(struct kxcjk1013_data *data, > enum kxcjk1013_mode mode) > { > @@ -955,18 +974,14 @@ static irqreturn_t kxcjk1013_trigger_handler(int irq, void *p) > struct iio_poll_func *pf = p; > struct iio_dev *indio_dev = pf->indio_dev; > struct kxcjk1013_data *data = iio_priv(indio_dev); > - int bit, ret, i = 0; > + int ret; > > mutex_lock(&data->mutex); > - for (bit = 0; bit < AXIS_MAX; bit++) { > - ret = kxcjk1013_get_acc_reg(data, bit); > - if (ret < 0) { > - mutex_unlock(&data->mutex); > - goto err; > - } > - data->buffer[i++] = ret; > - } > + ret = data->read_block_data(data->client, KXCJK1013_REG_XOUT_L, > + AXIS_MAX * 2, (u8 *) data->buffer); > mutex_unlock(&data->mutex); > + if (ret < 0) > + goto err; > > iio_push_to_buffers_with_timestamp(indio_dev, data->buffer, > data->timestamp); > @@ -1196,6 +1211,11 @@ static int kxcjk1013_probe(struct i2c_client *client, > const char *name; > int ret; > > + if (!i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_BYTE_DATA | > + I2C_FUNC_SMBUS_READ_WORD_DATA)) > + return -ENODEV; > + > indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); > if (!indio_dev) > return -ENOMEM; > @@ -1204,6 +1224,12 @@ static int kxcjk1013_probe(struct i2c_client *client, > i2c_set_clientdata(client, indio_dev); > data->client = client; > > + if (i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) > + data->read_block_data = i2c_smbus_read_i2c_block_data; > + else > + data->read_block_data = kxcjk1013_read_block_data; > + > pdata = dev_get_platdata(&client->dev); > if (pdata) > data->active_high_intr = pdata->active_high_intr; > -- Peter Meerwald +43-664-2444418 (mobile)