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Diffstat (limited to 'drivers/spi/spi-lm70llp.c')
| -rw-r--r-- | drivers/spi/spi-lm70llp.c | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/drivers/spi/spi-lm70llp.c b/drivers/spi/spi-lm70llp.c new file mode 100644 index 000000000..174dba29b --- /dev/null +++ b/drivers/spi/spi-lm70llp.c @@ -0,0 +1,339 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Driver for LM70EVAL-LLP board for the LM70 sensor + * + * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com> + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#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.rst. 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, + unsigned flags) +{ + return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); +} + +static void spi_lm70llp_attach(struct parport *p) +{ + struct pardevice *pd; + struct spi_lm70llp *pp; + struct spi_master *master; + int status; + struct pardev_cb lm70llp_cb; + + if (lm70llp) { + pr_warn("spi_lm70llp instance already loaded. Aborting.\n"); + 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; + memset(&lm70llp_cb, 0, sizeof(lm70llp_cb)); + lm70llp_cb.private = pp; + lm70llp_cb.flags = PARPORT_FLAG_EXCL; + pd = parport_register_dev_model(p, DRVNAME, &lm70llp_cb, 0); + + 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) { + dev_warn(&pd->dev, "spi_bitbang_start failed with status %d\n", + 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\n", + dev_name(&pp->spidev_lm70->dev)); + else { + dev_warn(&pd->dev, "spi_new_device failed\n"); + 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: + spi_master_put(master); +out_fail: + pr_info("spi_lm70llp probe fail, status %d\n", 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); + + spi_master_put(pp->bitbang.master); + + lm70llp = NULL; +} + +static struct parport_driver spi_lm70llp_drv = { + .name = DRVNAME, + .match_port = spi_lm70llp_attach, + .detach = spi_lm70llp_detach, + .devmodel = true, +}; + +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"); |