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Message-ID: <1F3AC3675D538145B1661F571FE1805F19A20D9C@irsmsx105.ger.corp.intel.com>
Date: Fri, 20 Feb 2015 12:02:19 +0000
From: "Tirdea, Irina" <irina.tirdea@...el.com>
To: Peter Meerwald <pmeerw@...erw.net>
CC: Jonathan Cameron <jic23@...nel.org>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
"Reus, Adriana" <adriana.reus@...el.com>
Subject: RE: [PATCH 2/2] iio: accel: kxcjk-1013: optimize i2c transfers in
trigger handler
> -----Original Message-----
> From: Peter Meerwald [mailto:pmeerw@...erw.net]
> Sent: 16 February, 2015 21:26
> To: Tirdea, Irina
> Cc: Jonathan Cameron; linux-iio@...r.kernel.org; linux-kernel@...r.kernel.org; Pandruvada, Srinivas; Reus, Adriana
> Subject: Re: [PATCH 2/2] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler
>
>
> > 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
>
Thanks for the review, Peter!
> > Signed-off-by: Adriana Reus <adriana.reus@...el.com>
> > Signed-off-by: Irina Tirdea <irina.tirdea@...el.com>
> > Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> > ---
> > 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?
>
Actually this is exactly what I did: adding this code in a couple of drivers :)
You are right, this belongs to the i2c core. Will move it there.
> > };
> >
> > 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
>
Good point. Changing the endianess to IIO_LE is correct for either kxcjk1013_read_block_data or i2c_smbus_read_i2c_block_data.
Will fix this in the next version. Thanks for catching this!
> > + }
> > + 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)
--
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