diff options
Diffstat (limited to 'drivers/spi/spi-lp8841-rtc.c')
| -rw-r--r-- | drivers/spi/spi-lp8841-rtc.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c new file mode 100644 index 000000000..faa577d28 --- /dev/null +++ b/drivers/spi/spi-lp8841-rtc.c @@ -0,0 +1,256 @@ +/* + * SPI master driver for ICP DAS LP-8841 RTC + * + * Copyright (C) 2016 Sergei Ianovich + * + * based on + * + * Dallas DS1302 RTC Support + * Copyright (C) 2002 David McCullough + * Copyright (C) 2003 - 2007 Paul Mundt + * + * 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. + */ +#include <linux/delay.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/spi/spi.h> + +#define DRIVER_NAME "spi_lp8841_rtc" + +#define SPI_LP8841_RTC_CE 0x01 +#define SPI_LP8841_RTC_CLK 0x02 +#define SPI_LP8841_RTC_nWE 0x04 +#define SPI_LP8841_RTC_MOSI 0x08 +#define SPI_LP8841_RTC_MISO 0x01 + +/* + * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI + * GPIO driver, this SPI driver can be replaced by a simple GPIO driver + * providing 3 GPIO pins. + */ + +struct spi_lp8841_rtc { + void *iomem; + unsigned long state; +}; + +static inline void +setsck(struct spi_lp8841_rtc *data, int is_on) +{ + if (is_on) + data->state |= SPI_LP8841_RTC_CLK; + else + data->state &= ~SPI_LP8841_RTC_CLK; + writeb(data->state, data->iomem); +} + +static inline void +setmosi(struct spi_lp8841_rtc *data, int is_on) +{ + if (is_on) + data->state |= SPI_LP8841_RTC_MOSI; + else + data->state &= ~SPI_LP8841_RTC_MOSI; + writeb(data->state, data->iomem); +} + +static inline int +getmiso(struct spi_lp8841_rtc *data) +{ + return ioread8(data->iomem) & SPI_LP8841_RTC_MISO; +} + +static inline u32 +bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data, + unsigned usecs, unsigned cpol, unsigned flags, + u32 word, u8 bits) +{ + /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ + + u32 shift = 32 - bits; + /* clock starts at inactive polarity */ + for (; likely(bits); bits--) { + + /* setup LSB (to slave) on leading edge */ + if ((flags & SPI_MASTER_NO_TX) == 0) + setmosi(data, (word & 1)); + + usleep_range(usecs, usecs + 1); /* T(setup) */ + + /* sample LSB (from slave) on trailing edge */ + word >>= 1; + if ((flags & SPI_MASTER_NO_RX) == 0) + word |= (getmiso(data) << 31); + + setsck(data, !cpol); + usleep_range(usecs, usecs + 1); + + setsck(data, cpol); + } + + word >>= shift; + return word; +} + +static int +spi_lp8841_rtc_transfer_one(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *t) +{ + struct spi_lp8841_rtc *data = spi_master_get_devdata(master); + unsigned count = t->len; + const u8 *tx = t->tx_buf; + u8 *rx = t->rx_buf; + u8 word = 0; + int ret = 0; + + if (tx) { + data->state &= ~SPI_LP8841_RTC_nWE; + writeb(data->state, data->iomem); + while (likely(count > 0)) { + word = *tx++; + bitbang_txrx_be_cpha0_lsb(data, 1, 0, + SPI_MASTER_NO_RX, word, 8); + count--; + } + } else if (rx) { + data->state |= SPI_LP8841_RTC_nWE; + writeb(data->state, data->iomem); + while (likely(count > 0)) { + word = bitbang_txrx_be_cpha0_lsb(data, 1, 0, + SPI_MASTER_NO_TX, word, 8); + *rx++ = word; + count--; + } + } else { + ret = -EINVAL; + } + + spi_finalize_current_transfer(master); + + return ret; +} + +static void +spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable) +{ + struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master); + + data->state = 0; + writeb(data->state, data->iomem); + if (enable) { + usleep_range(4, 5); + data->state |= SPI_LP8841_RTC_CE; + writeb(data->state, data->iomem); + usleep_range(4, 5); + } +} + +static int +spi_lp8841_rtc_setup(struct spi_device *spi) +{ + if ((spi->mode & SPI_CS_HIGH) == 0) { + dev_err(&spi->dev, "unsupported active low chip select\n"); + return -EINVAL; + } + + if ((spi->mode & SPI_LSB_FIRST) == 0) { + dev_err(&spi->dev, "unsupported MSB first mode\n"); + return -EINVAL; + } + + if ((spi->mode & SPI_3WIRE) == 0) { + dev_err(&spi->dev, "unsupported wiring. 3 wires required\n"); + return -EINVAL; + } + + return 0; +} + +#ifdef CONFIG_OF +static const struct of_device_id spi_lp8841_rtc_dt_ids[] = { + { .compatible = "icpdas,lp8841-spi-rtc" }, + { } +}; + +MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids); +#endif + +static int +spi_lp8841_rtc_probe(struct platform_device *pdev) +{ + int ret; + struct spi_master *master; + struct spi_lp8841_rtc *data; + void *iomem; + + master = spi_alloc_master(&pdev->dev, sizeof(*data)); + if (!master) + return -ENOMEM; + platform_set_drvdata(pdev, master); + + master->flags = SPI_MASTER_HALF_DUPLEX; + master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST; + + master->bus_num = pdev->id; + master->num_chipselect = 1; + master->setup = spi_lp8841_rtc_setup; + master->set_cs = spi_lp8841_rtc_set_cs; + master->transfer_one = spi_lp8841_rtc_transfer_one; + master->bits_per_word_mask = SPI_BPW_MASK(8); +#ifdef CONFIG_OF + master->dev.of_node = pdev->dev.of_node; +#endif + + data = spi_master_get_devdata(master); + + iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0); + data->iomem = devm_ioremap_resource(&pdev->dev, iomem); + ret = PTR_ERR_OR_ZERO(data->iomem); + if (ret) { + dev_err(&pdev->dev, "failed to get IO address\n"); + goto err_put_master; + } + + /* register with the SPI framework */ + ret = devm_spi_register_master(&pdev->dev, master); + if (ret) { + dev_err(&pdev->dev, "cannot register spi master\n"); + goto err_put_master; + } + + return ret; + + +err_put_master: + spi_master_put(master); + + return ret; +} + +MODULE_ALIAS("platform:" DRIVER_NAME); + +static struct platform_driver spi_lp8841_rtc_driver = { + .driver = { + .name = DRIVER_NAME, + .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids), + }, + .probe = spi_lp8841_rtc_probe, +}; +module_platform_driver(spi_lp8841_rtc_driver); + +MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC"); +MODULE_AUTHOR("Sergei Ianovich"); +MODULE_LICENSE("GPL"); |