iio: st_sensors: read each channel individually
The current buffer read code tries to optimize reads from the sensor data registers by issuing a single read operation across all the indata registers. This doesn't work: when the LIS331DL accelerometer sensor is configured to open drain, active low interrupt mode, this will just clear the XDA (X-axis data available) bit in the STATUS_REG register (0x27), while YDA, ZDA and even ZYXDA remain set to 1, and the internal logic of the sensor holds the DRDY (INT1) line asserted (the value of the status register is 0xee). If we instead issue one read operation per enabled channel (X, Y, Z) things start working and we can use open drain and active low interrupts. Note that a backported patch fixing this issue will be heading via the fixes branch but changes in this file already in staging-next will make that patch 'look' rather different. The code in here is the correct one when that clash hits. Cc: Giuseppe Barba <giuseppe.barba@st.com> Cc: Denis Ciocca <denis.ciocca@st.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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@ -24,67 +24,30 @@
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int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
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{
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u8 addr[3]; /* no ST sensor has more than 3 channels */
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int i, n = 0, len;
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int i, len;
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int total = 0;
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struct st_sensor_data *sdata = iio_priv(indio_dev);
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unsigned int num_data_channels = sdata->num_data_channels;
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unsigned int byte_for_channel =
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indio_dev->channels[0].scan_type.storagebits >> 3;
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for (i = 0; i < num_data_channels; i++) {
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unsigned int bytes_to_read;
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if (test_bit(i, indio_dev->active_scan_mask)) {
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addr[n] = indio_dev->channels[i].address;
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n++;
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bytes_to_read = indio_dev->channels[i].scan_type.storagebits >> 3;
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len = sdata->tf->read_multiple_byte(&sdata->tb,
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sdata->dev, indio_dev->channels[i].address,
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bytes_to_read,
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buf + total, sdata->multiread_bit);
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if (len < bytes_to_read)
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return -EIO;
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/* Advance the buffer pointer */
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total += len;
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}
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}
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switch (n) {
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case 1:
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len = sdata->tf->read_multiple_byte(&sdata->tb, sdata->dev,
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addr[0], byte_for_channel, buf, sdata->multiread_bit);
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break;
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case 2:
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if ((addr[1] - addr[0]) == byte_for_channel) {
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len = sdata->tf->read_multiple_byte(&sdata->tb,
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sdata->dev, addr[0], byte_for_channel * n,
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buf, sdata->multiread_bit);
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} else {
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u8 *rx_array;
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rx_array = kmalloc(byte_for_channel * num_data_channels,
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GFP_KERNEL);
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if (!rx_array)
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return -ENOMEM;
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len = sdata->tf->read_multiple_byte(&sdata->tb,
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sdata->dev, addr[0],
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byte_for_channel * num_data_channels,
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rx_array, sdata->multiread_bit);
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if (len < 0) {
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kfree(rx_array);
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return len;
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}
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for (i = 0; i < n * byte_for_channel; i++) {
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if (i < n)
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buf[i] = rx_array[i];
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else
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buf[i] = rx_array[n + i];
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}
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kfree(rx_array);
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len = byte_for_channel * n;
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}
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break;
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case 3:
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len = sdata->tf->read_multiple_byte(&sdata->tb, sdata->dev,
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addr[0], byte_for_channel * num_data_channels,
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buf, sdata->multiread_bit);
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break;
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default:
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return -EINVAL;
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}
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if (len != byte_for_channel * n)
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return -EIO;
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return len;
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return total;
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}
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EXPORT_SYMBOL(st_sensors_get_buffer_element);
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