/**
 * SPI Driver for LM95071 temperature sensor device.  This is implemented
 * specifically in the context of the Atheros 953x GFMN board, and not meant to
 * be a general solution (a more robust solution would likely be implemented
 * using a parport interface).
 *
 * The LM95071 temperature sensor uses a 3-pin SPI interface.  On this board,
 * the device shares the MISO and CLK pins with the flash device.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/sysfs.h>
#include <linux/hwmon.h>
#include <linux/spi/spi.h>
#include <asm/delay.h>
#include <atheros.h>

#include "ath_mn_lm95071.h"

#define DRVNAME "lm95071"

struct lm95071 {
  struct device *dev;
  void (*lock)(void);
  void (*unlock)(void);
};

static void lm_lock(void) {
  ath_mn_spi_enable_cs();
  lm_spi_func_clear();
  ath_gpio_drive_low(ATH_MN_TEMP_SENSOR_PIN);
  lm_delay();
}

static void lm_unlock(void) {
  ath_gpio_drive_high(ATH_MN_TEMP_SENSOR_PIN);
  lm_spi_func_restore();
  ath_mn_spi_disable_cs();
}

static struct lm95071 lm_dev = {
  .dev         = NULL,
  .lock        = lm_lock,
  .unlock      = lm_unlock,
};

/* Enables continuous conversion mode. */
static void lm95071_enable_cc(void)
{
  lm_dev.lock();
  lm_spi_delay_16();
  lm_spi_delay_8();
  lm_spi_bit_banger(LM_MODE_CC);
  lm_dev.unlock();
}

static int lm95071_detect(void)
{
  /* TODO(awdavies) Implement this function to read the ID register. */
  return 0;
}

static ssize_t lm95071_get_temperature(struct device *dev,
                                       struct device_attribute *attr, char *buf)
{
  s64 temp;
  u16 raw_temp, sign;
  lm_dev.lock();
  lm_spi_delay_16();
  raw_temp = lm_spi_rd_16();
  lm_dev.unlock();
  sign = 0x8000 & raw_temp;
  if (sign) {
    raw_temp = ~raw_temp + 1;
  }
  /*
   * LM90571 Temp register has two unused bits at the end.  After these are
   * removed, every number remaining corresponds to 0.03125 C of temperature.
   *
   * Official docs here: http://www.ti.com/lit/ds/symlink/lm95071.pdf
   */
  temp = raw_temp >> 2;
  temp *= 3125;
  do_div(temp, 100);
  return sprintf(buf, "%lld\n", sign ? -temp : temp);
}

static DEVICE_ATTR(temp1_input, S_IRUGO, lm95071_get_temperature, NULL);

static ssize_t lm95071_get_name(struct device *dev,
                                struct device_attribute *devattr, char *buf)
{
  return sprintf(buf, "%s\n", DRVNAME);
}

static DEVICE_ATTR(name, S_IRUGO, lm95071_get_name, NULL);

static int lm95071_probe(void)
{
  int res;
  if (lm95071_detect()) {
    printk(KERN_NOTICE "hwmon_dev_detect failed (lm95071)\n");
    res = -ENOENT;
    goto dev_detect_failed;
  }
  lm95071_enable_cc();
  lm_dev.dev = hwmon_device_register(NULL);
  if (IS_ERR(lm_dev.dev)) {
    printk(KERN_NOTICE "%x hwmon_dev_reg failed (lm95071)\n", lm_dev.dev);
    res = PTR_ERR(lm_dev.dev);
    goto dev_reg_failed;
  }
  dev_set_drvdata(lm_dev.dev, &lm_dev);
  /* Here is where sysfs gets hooked. */
  if ((res = device_create_file(lm_dev.dev, &dev_attr_temp1_input))
      || (res = device_create_file(lm_dev.dev, &dev_attr_name))) {
    printk(KERN_NOTICE "hwmon_dev_create failed (lm95071)\n");
    goto dev_create_failed;
  }
  /* Sanity check. */
  printk(KERN_NOTICE "lm95071 temp sensor driver initialized.\n");
  return 0;

dev_create_failed:
  device_remove_file(lm_dev.dev, &dev_attr_temp1_input);
  hwmon_device_unregister(lm_dev.dev);
dev_reg_failed:
  dev_set_drvdata(lm_dev.dev, NULL);
dev_detect_failed:
  return res;
}

static void lm95071_remove(void)
{
  device_remove_file(lm_dev.dev, &dev_attr_temp1_input);
  device_remove_file(lm_dev.dev, &dev_attr_name);
  hwmon_device_unregister(lm_dev.dev);
  dev_set_drvdata(lm_dev.dev, NULL);
}

static int __init init_lm95071(void)
{
  return lm95071_probe();
}

static void __exit cleanup_lm95071(void)
{
  lm95071_remove();
}

module_init(init_lm95071);
module_exit(cleanup_lm95071);