/*
   * Driver for LM70EVAL-LLP board for the LM70 sensor
   *
   * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/delay.h>
  #include <linux/device.h>
  #include <linux/parport.h>
  #include <linux/sysfs.h>
  #include <linux/workqueue.h>
  
  
  #include <linux/spi/spi.h>
  #include <linux/spi/spi_bitbang.h>
  
  
  /*
   * The LM70 communicates with a host processor using a 3-wire variant of
   * the SPI/Microwire bus interface. This driver specifically supports an
   * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
   * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
   * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
   * driver", layered on top of this one and usable without the lm70llp.
   *
   * Datasheet and Schematic:
   * The LM70 is a temperature sensor chip from National Semiconductor; its
   * datasheet is available at http://www.national.com/pf/LM/LM70.html
   * The schematic for this particular board (the LM70EVAL-LLP) is
   * available (on page 4) here:
   *  http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
   *
   * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
   * (heavily) based on spi-butterfly by David Brownell.
   *
   * The LM70 LLP connects to the PC parallel port in the following manner:
   *
   *   Parallel                 LM70 LLP
   *     Port      Direction   JP2 Header
   *  -----------  ---------  ------------
   *      D0    2      -         -
   *      D1    3     -->      V+   5
   *      D2    4     -->      V+   5
   *      D3    5     -->      V+   5
   *      D4    6     -->      V+   5
   *      D5    7     -->      nCS  8
   *      D6    8     -->      SCLK 3
   *      D7    9     -->      SI/O 5
   *     GND   25      -       GND  7
   *    Select 13     <--      SI/O 1
   *
   * Note that parport pin 13 actually gets inverted by the transistor
   * arrangement which lets either the parport or the LM70 drive the
   * SI/SO signal (see the schematic for details).
   */
  
  #define DRVNAME		"spi-lm70llp"
  
  #define lm70_INIT	0xBE
  #define SIO		0x10
  #define nCS		0x20
  #define SCLK		0x40
  
  /*-------------------------------------------------------------------------*/
  
  struct spi_lm70llp {
  	struct spi_bitbang	bitbang;
  	struct parport		*port;
  	struct pardevice	*pd;
  	struct spi_device	*spidev_lm70;
  	struct spi_board_info	info;
  	//struct device		*dev;
  };
  
  /* REVISIT : ugly global ; provides "exclusive open" facility */
  static struct spi_lm70llp *lm70llp;
  
  
  /*-------------------------------------------------------------------*/
  
  static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
  {
  	return spi->controller_data;
  }
  
  /*---------------------- LM70 LLP eval board-specific inlines follow */
  
  /* NOTE:  we don't actually need to reread the output values, since they'll
   * still be what we wrote before.  Plus, going through parport builds in
   * a ~1ms/operation delay; these SPI transfers could easily be faster.
   */
  
  static inline void deassertCS(struct spi_lm70llp *pp)
  {
  	u8 data = parport_read_data(pp->port);
  
  	data &= ~0x80;		/* pull D7/SI-out low while de-asserted */
  	parport_write_data(pp->port, data | nCS);
  }
  
  static inline void assertCS(struct spi_lm70llp *pp)
  {
  	u8 data = parport_read_data(pp->port);
  
  	data |= 0x80;		/* pull D7/SI-out high so lm70 drives SO-in */
  	parport_write_data(pp->port, data & ~nCS);
  }
  
  static inline void clkHigh(struct spi_lm70llp *pp)
  {
  	u8 data = parport_read_data(pp->port);
  	parport_write_data(pp->port, data | SCLK);
  }
  
  static inline void clkLow(struct spi_lm70llp *pp)
  {
  	u8 data = parport_read_data(pp->port);
  	parport_write_data(pp->port, data & ~SCLK);
  }
  
  /*------------------------- SPI-LM70-specific inlines ----------------------*/
  
  static inline void spidelay(unsigned d)
  {
  	udelay(d);
  }
  
  static inline void setsck(struct spi_device *s, int is_on)
  {
  	struct spi_lm70llp *pp = spidev_to_pp(s);
  
  	if (is_on)
  		clkHigh(pp);
  	else
  		clkLow(pp);
  }
  
  static inline void setmosi(struct spi_device *s, int is_on)
  {
  	/* FIXME update D7 ... this way we can put the chip
  	 * into shutdown mode and read the manufacturer ID,
  	 * but we can't put it back into operational mode.
  	 */
  }
  
  /*
   * getmiso:
   * Why do we return 0 when the SIO line is high and vice-versa?
   * The fact is, the lm70 eval board from NS (which this driver drives),
   * is wired in just such a way : when the lm70's SIO goes high, a transistor
   * switches it to low reflecting this on the parport (pin 13), and vice-versa.
   */
  static inline int getmiso(struct spi_device *s)
  {
  	struct spi_lm70llp *pp = spidev_to_pp(s);
  	return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
  }
  /*--------------------------------------------------------------------*/
  
  #include "spi-bitbang-txrx.h"
  
  static void lm70_chipselect(struct spi_device *spi, int value)
  {
  	struct spi_lm70llp *pp = spidev_to_pp(spi);
  
  	if (value)
  		assertCS(pp);
  	else
  		deassertCS(pp);
  }
  
  /*
   * Our actual bitbanger routine.
   */
  static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
  {
  	return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
  }
  
  static void spi_lm70llp_attach(struct parport *p)
  {
  	struct pardevice	*pd;
  	struct spi_lm70llp	*pp;
  	struct spi_master	*master;
  	int			status;
  
  	if (lm70llp) {
  		printk(KERN_WARNING
  			"%s: spi_lm70llp instance already loaded. Aborting.
  ",
  			DRVNAME);
  		return;
  	}
  
  	/* TODO:  this just _assumes_ a lm70 is there ... no probe;
  	 * the lm70 driver could verify it, reading the manf ID.
  	 */
  
  	master = spi_alloc_master(p->physport->dev, sizeof *pp);
  	if (!master) {
  		status = -ENOMEM;
  		goto out_fail;
  	}
  	pp = spi_master_get_devdata(master);
  
  	/*
  	 * SPI and bitbang hookup.
  	 */
  	pp->bitbang.master = master;
  	pp->bitbang.chipselect = lm70_chipselect;
  	pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
  	pp->bitbang.flags = SPI_3WIRE;
  
  	/*
  	 * Parport hookup
  	 */
  	pp->port = p;
  	pd = parport_register_device(p, DRVNAME,
  			NULL, NULL, NULL,
  			PARPORT_FLAG_EXCL, pp);
  	if (!pd) {
  		status = -ENOMEM;
  		goto out_free_master;
  	}
  	pp->pd = pd;
  
  	status = parport_claim(pd);
  	if (status < 0)
  		goto out_parport_unreg;
  
  	/*
  	 * Start SPI ...
  	 */
  	status = spi_bitbang_start(&pp->bitbang);
  	if (status < 0) {
  		printk(KERN_WARNING
  			"%s: spi_bitbang_start failed with status %d
  ",
  			DRVNAME, status);
  		goto out_off_and_release;
  	}
  
  	/*
  	 * The modalias name MUST match the device_driver name
  	 * for the bus glue code to match and subsequently bind them.
  	 * We are binding to the generic drivers/hwmon/lm70.c device
  	 * driver.
  	 */
  	strcpy(pp->info.modalias, "lm70");
  	pp->info.max_speed_hz = 6 * 1000 * 1000;
  	pp->info.chip_select = 0;
  	pp->info.mode = SPI_3WIRE | SPI_MODE_0;
  
  	/* power up the chip, and let the LM70 control SI/SO */
  	parport_write_data(pp->port, lm70_INIT);
  
  	/* Enable access to our primary data structure via
  	 * the board info's (void *)controller_data.
  	 */
  	pp->info.controller_data = pp;
  	pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
  	if (pp->spidev_lm70)
  		dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s
  ",
  				dev_name(&pp->spidev_lm70->dev));
  	else {
  		printk(KERN_WARNING "%s: spi_new_device failed
  ", DRVNAME);
  		status = -ENODEV;
  		goto out_bitbang_stop;
  	}
  	pp->spidev_lm70->bits_per_word = 8;
  
  	lm70llp = pp;
  	return;
  
  out_bitbang_stop:
  	spi_bitbang_stop(&pp->bitbang);
  out_off_and_release:
  	/* power down */
  	parport_write_data(pp->port, 0);
  	mdelay(10);
  	parport_release(pp->pd);
  out_parport_unreg:
  	parport_unregister_device(pd);
  out_free_master:
  	(void) spi_master_put(master);
  out_fail:
  	pr_info("%s: spi_lm70llp probe fail, status %d
  ", DRVNAME, status);
  }
  
  static void spi_lm70llp_detach(struct parport *p)
  {
  	struct spi_lm70llp		*pp;
  
  	if (!lm70llp || lm70llp->port != p)
  		return;
  
  	pp = lm70llp;
  	spi_bitbang_stop(&pp->bitbang);
  
  	/* power down */
  	parport_write_data(pp->port, 0);
  
  	parport_release(pp->pd);
  	parport_unregister_device(pp->pd);
  
  	(void) spi_master_put(pp->bitbang.master);
  
  	lm70llp = NULL;
  }
  
  
  static struct parport_driver spi_lm70llp_drv = {
  	.name =		DRVNAME,
  	.attach =	spi_lm70llp_attach,
  	.detach =	spi_lm70llp_detach,
  };
  
  static int __init init_spi_lm70llp(void)
  {
  	return parport_register_driver(&spi_lm70llp_drv);
  }
  module_init(init_spi_lm70llp);
  
  static void __exit cleanup_spi_lm70llp(void)
  {
  	parport_unregister_driver(&spi_lm70llp_drv);
  }
  module_exit(cleanup_spi_lm70llp);
  
  MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
  MODULE_DESCRIPTION(
  	"Parport adapter for the National Semiconductor LM70 LLP eval board");
  MODULE_LICENSE("GPL");