drivers/staging/iio/accel/sca3000_ring.c

   1 /*
   2  * sca3000_ring.c -- support VTI sca3000 series accelerometers via SPI
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * Copyright (c) 2009 Jonathan Cameron <jic23@cam.ac.uk>
   9  *
  10  */
  11
  12 #include <linux/interrupt.h>
  13 #include <linux/gpio.h>
  14 #include <linux/fs.h>
  15 #include <linux/device.h>
  16 #include <linux/slab.h>
  17 #include <linux/kernel.h>
  18 #include <linux/spi/spi.h>
  19 #include <linux/sysfs.h>
  20
  21 #include "../iio.h"
  22 #include "../sysfs.h"
  23 #include "../ring_generic.h"
  24 #include "../ring_hw.h"
  25 #include "accel.h"
  26 #include "sca3000.h"
  27
  28 /* RFC / future work
  29  *
  30  * The internal ring buffer doesn't actually change what it holds depending
  31  * on which signals are enabled etc, merely whether you can read them.
  32  * As such the scan mode selection is somewhat different than for a software
  33  * ring buffer and changing it actually covers any data already in the buffer.
  34  * Currently scan elements aren't configured so it doesn't matter.
  35  */
  36
  37 /**
  38  * sca3000_rip_hw_rb() - main ring access function, pulls data from ring
  39  * @r:                  the ring
  40  * @count:              number of samples to try and pull
  41  * @data:               output the actual samples pulled from the hw ring
  42  * @dead_offset:        cheating a bit here: Set to 1 so as to allow for the
  43  *                      leading byte used in bus comms.
  44  *
  45  * Currently does not provide timestamps.  As the hardware doesn't add them they
  46  * can only be inferred aproximately from ring buffer events such as 50% full
  47  * and knowledge of when buffer was last emptied.  This is left to userspace.
  48  **/
  49 static int sca3000_rip_hw_rb(struct iio_ring_buffer *r,
  50                              size_t count, u8 **data, int *dead_offset)
  51 {
  52         struct iio_hw_ring_buffer *hw_ring = iio_to_hw_ring_buf(r);
  53         struct iio_dev *indio_dev = hw_ring->private;
  54         struct sca3000_state *st = indio_dev->dev_data;
  55         u8 *rx;
  56         int ret, num_available, num_read = 0;
  57         int bytes_per_sample = 1;
  58
  59         if (st->bpse == 11)
  60                 bytes_per_sample = 2;
  61
  62         mutex_lock(&st->lock);
  63         /* Check how much data is available:
  64          * RFC: Implement an ioctl to not bother checking whether there
  65          * is enough data in the ring?  Afterall, if we are responding
  66          * to an interrupt we have a minimum content guaranteed so it
  67          * seems slight silly to waste time checking it is there.
  68          */
  69         ret = sca3000_read_data(st,
  70                                 SCA3000_REG_ADDR_BUF_COUNT,
  71                                 &rx, 1);
  72         if (ret)
  73                 goto error_ret;
  74         else
  75                 num_available = rx[1];
  76         /* num_available is the total number of samples available
  77          * i.e. number of time points * number of channels.
  78          */
  79         kfree(rx);
  80         if (count > num_available * bytes_per_sample)
  81                 num_read = num_available*bytes_per_sample;
  82         else
  83                 num_read = count - (count % (bytes_per_sample));
  84
  85         /* Avoid the read request byte */
  86         *dead_offset = 1;
  87         ret = sca3000_read_data(st,
  88                                 SCA3000_REG_ADDR_RING_OUT,
  89                                 data, num_read);
  90 error_ret:
  91         mutex_unlock(&st->lock);
  92
  93         return ret ? ret : num_read;
  94 }
  95
  96 /* This is only valid with all 3 elements enabled */
  97 static int sca3000_ring_get_length(struct iio_ring_buffer *r)
  98 {
  99         return 64;
 100 }
 101
 102 /* only valid if resolution is kept at 11bits */
 103 static int sca3000_ring_get_bpd(struct iio_ring_buffer *r)
 104 {
 105         return 6;
 106 }
 107 static void sca3000_ring_release(struct device *dev)
 108 {
 109         struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
 110         kfree(iio_to_hw_ring_buf(r));
 111 }
 112
 113 static IIO_RING_ENABLE_ATTR;
 114 static IIO_RING_BPS_ATTR;
 115 static IIO_RING_LENGTH_ATTR;
 116
 117 /**
 118  * sca3000_show_ring_bpse() -sysfs function to query bits per sample from ring
 119  * @dev: ring buffer device
 120  * @attr: this device attribute
 121  * @buf: buffer to write to
 122  **/
 123 static ssize_t sca3000_show_ring_bpse(struct device *dev,
 124                                       struct device_attribute *attr,
 125                                       char *buf)
 126 {
 127         int len = 0, ret;
 128         u8 *rx;
 129         struct iio_ring_buffer *r = dev_get_drvdata(dev);
 130         struct sca3000_state *st = r->indio_dev->dev_data;
 131
 132         mutex_lock(&st->lock);
 133         ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
 134         if (ret)
 135                 goto error_ret;
 136         len = sprintf(buf, "%d\n", (rx[1] & SCA3000_RING_BUF_8BIT) ? 8 : 11);
 137         kfree(rx);
 138 error_ret:
 139         mutex_unlock(&st->lock);
 140
 141         return ret ? ret : len;
 142 }
 143
 144 /**
 145  * sca3000_store_ring_bpse() - bits per scan element
 146  * @dev: ring buffer device
 147  * @attr: attribute called from
 148  * @buf: input from userspace
 149  * @len: length of input
 150  **/
 151 static ssize_t sca3000_store_ring_bpse(struct device *dev,
 152                                       struct device_attribute *attr,
 153                                       const char *buf,
 154                                       size_t len)
 155 {
 156         struct iio_ring_buffer *r = dev_get_drvdata(dev);
 157         struct sca3000_state *st = r->indio_dev->dev_data;
 158         int ret;
 159         u8 *rx;
 160         long val;
 161         ret = strict_strtol(buf, 10, &val);
 162         if (ret)
 163                 return ret;
 164
 165         mutex_lock(&st->lock);
 166
 167         ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
 168         if (!ret)
 169                 switch (val) {
 170                 case 8:
 171                         ret = sca3000_write_reg(st, SCA3000_REG_ADDR_MODE,
 172                                                 rx[1] | SCA3000_RING_BUF_8BIT);
 173                         st->bpse = 8;
 174                         break;
 175                 case 11:
 176                         ret = sca3000_write_reg(st, SCA3000_REG_ADDR_MODE,
 177                                                 rx[1] & ~SCA3000_RING_BUF_8BIT);
 178                         st->bpse = 11;
 179                         break;
 180                 default:
 181                         ret = -EINVAL;
 182                         break;
 183                 }
 184         mutex_unlock(&st->lock);
 185
 186         return ret ? ret : len;
 187 }
 188
 189 static IIO_CONST_ATTR(bpse_available, "8 11");
 190
 191 static IIO_DEV_ATTR_BPSE(S_IRUGO | S_IWUSR,
 192                               sca3000_show_ring_bpse,
 193                               sca3000_store_ring_bpse);
 194
 195 /*
 196  * Ring buffer attributes
 197  * This device is a bit unusual in that the sampling frequency and bpse
 198  * only apply to the ring buffer.  At all times full rate and accuracy
 199  * is available via direct reading from registers.
 200  */
 201 static struct attribute *iio_ring_attributes[] = {
 202         &dev_attr_length.attr,
 203         &dev_attr_bps.attr,
 204         &dev_attr_ring_enable.attr,
 205         &iio_dev_attr_bpse.dev_attr.attr,
 206         &iio_const_attr_bpse_available.dev_attr.attr,
 207         NULL,
 208 };
 209
 210 static struct attribute_group sca3000_ring_attr = {
 211         .attrs = iio_ring_attributes,
 212 };
 213
 214 static const struct attribute_group *sca3000_ring_attr_groups[] = {
 215         &sca3000_ring_attr,
 216         NULL
 217 };
 218
 219 static struct device_type sca3000_ring_type = {
 220         .release = sca3000_ring_release,
 221         .groups = sca3000_ring_attr_groups,
 222 };
 223
 224 static struct iio_ring_buffer *sca3000_rb_allocate(struct iio_dev *indio_dev)
 225 {
 226         struct iio_ring_buffer *buf;
 227         struct iio_hw_ring_buffer *ring;
 228
 229         ring = kzalloc(sizeof *ring, GFP_KERNEL);
 230         if (!ring)
 231                 return 0;
 232         ring->private = indio_dev;
 233         buf = &ring->buf;
 234         iio_ring_buffer_init(buf, indio_dev);
 235         buf->dev.type = &sca3000_ring_type;
 236         device_initialize(&buf->dev);
 237         buf->dev.parent = &indio_dev->dev;
 238         dev_set_drvdata(&buf->dev, (void *)buf);
 239
 240         return buf;
 241 }
 242
 243 static inline void sca3000_rb_free(struct iio_ring_buffer *r)
 244 {
 245         if (r)
 246                 iio_put_ring_buffer(r);
 247 }
 248
 249 int sca3000_configure_ring(struct iio_dev *indio_dev)
 250 {
 251         indio_dev->ring = sca3000_rb_allocate(indio_dev);
 252         if (indio_dev->ring == NULL)
 253                 return -ENOMEM;
 254         indio_dev->modes |= INDIO_RING_HARDWARE_BUFFER;
 255
 256         indio_dev->ring->access.rip_lots = &sca3000_rip_hw_rb;
 257         indio_dev->ring->access.get_length = &sca3000_ring_get_length;
 258         indio_dev->ring->access.get_bpd = &sca3000_ring_get_bpd;
 259
 260         return 0;
 261 }
 262
 263 void sca3000_unconfigure_ring(struct iio_dev *indio_dev)
 264 {
 265         sca3000_rb_free(indio_dev->ring);
 266 }
 267
 268 static inline
 269 int __sca3000_hw_ring_state_set(struct iio_dev *indio_dev, bool state)
 270 {
 271         struct sca3000_state *st = indio_dev->dev_data;
 272         int ret;
 273         u8 *rx;
 274
 275         mutex_lock(&st->lock);
 276         ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
 277         if (ret)
 278                 goto error_ret;
 279         if (state) {
 280                 printk(KERN_INFO "supposedly enabling ring buffer\n");
 281                 ret = sca3000_write_reg(st,
 282                                         SCA3000_REG_ADDR_MODE,
 283                                         (rx[1] | SCA3000_RING_BUF_ENABLE));
 284         } else
 285                 ret = sca3000_write_reg(st,
 286                                         SCA3000_REG_ADDR_MODE,
 287                                         (rx[1] & ~SCA3000_RING_BUF_ENABLE));
 288         kfree(rx);
 289 error_ret:
 290         mutex_unlock(&st->lock);
 291
 292         return ret;
 293 }
 294 /**
 295  * sca3000_hw_ring_preenable() hw ring buffer preenable function
 296  *
 297  * Very simple enable function as the chip will allows normal reads
 298  * during ring buffer operation so as long as it is indeed running
 299  * before we notify the core, the precise ordering does not matter.
 300  **/
 301 static int sca3000_hw_ring_preenable(struct iio_dev *indio_dev)
 302 {
 303         return __sca3000_hw_ring_state_set(indio_dev, 1);
 304 }
 305
 306 static int sca3000_hw_ring_postdisable(struct iio_dev *indio_dev)
 307 {
 308         return __sca3000_hw_ring_state_set(indio_dev, 0);
 309 }
 310
 311 void sca3000_register_ring_funcs(struct iio_dev *indio_dev)
 312 {
 313         indio_dev->ring->preenable = &sca3000_hw_ring_preenable;
 314         indio_dev->ring->postdisable = &sca3000_hw_ring_postdisable;
 315 }
 316
 317 /**
 318  * sca3000_ring_int_process() ring specific interrupt handling.
 319  *
 320  * This is only split from the main interrupt handler so as to
 321  * reduce the amount of code if the ring buffer is not enabled.
 322  **/
 323 void sca3000_ring_int_process(u8 val, struct iio_ring_buffer *ring)
 324 {
 325         if (val & SCA3000_INT_STATUS_THREE_QUARTERS)
 326                 iio_push_or_escallate_ring_event(ring,
 327                                                  IIO_EVENT_CODE_RING_75_FULL,
 328                                                  0);
 329         else if (val & SCA3000_INT_STATUS_HALF)
 330                 iio_push_ring_event(ring,
 331                                     IIO_EVENT_CODE_RING_50_FULL, 0);
 332 }