1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * SPI master driver for ICP DAS LP-8841 RTC 4 * 5 * Copyright (C) 2016 Sergei Ianovich 6 * 7 * based on 8 * 9 * Dallas DS1302 RTC Support 10 * Copyright (C) 2002 David McCullough 11 * Copyright (C) 2003 - 2007 Paul Mundt 12 */ 13 #include <linux/delay.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/platform_device.h> 17 #include <linux/of.h> 18 #include <linux/spi/spi.h> 19 20 #define DRIVER_NAME "spi_lp8841_rtc" 21 22 #define SPI_LP8841_RTC_CE 0x01 23 #define SPI_LP8841_RTC_CLK 0x02 24 #define SPI_LP8841_RTC_nWE 0x04 25 #define SPI_LP8841_RTC_MOSI 0x08 26 #define SPI_LP8841_RTC_MISO 0x01 27 28 /* 29 * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI 30 * GPIO driver, this SPI driver can be replaced by a simple GPIO driver 31 * providing 3 GPIO pins. 32 */ 33 34 struct spi_lp8841_rtc { 35 void *iomem; 36 unsigned long state; 37 }; 38 39 static inline void 40 setsck(struct spi_lp8841_rtc *data, int is_on) 41 { 42 if (is_on) 43 data->state |= SPI_LP8841_RTC_CLK; 44 else 45 data->state &= ~SPI_LP8841_RTC_CLK; 46 writeb(data->state, data->iomem); 47 } 48 49 static inline void 50 setmosi(struct spi_lp8841_rtc *data, int is_on) 51 { 52 if (is_on) 53 data->state |= SPI_LP8841_RTC_MOSI; 54 else 55 data->state &= ~SPI_LP8841_RTC_MOSI; 56 writeb(data->state, data->iomem); 57 } 58 59 static inline int 60 getmiso(struct spi_lp8841_rtc *data) 61 { 62 return ioread8(data->iomem) & SPI_LP8841_RTC_MISO; 63 } 64 65 static inline u32 66 bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data, 67 unsigned usecs, unsigned cpol, unsigned flags, 68 u32 word, u8 bits) 69 { 70 /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ 71 72 u32 shift = 32 - bits; 73 /* clock starts at inactive polarity */ 74 for (; likely(bits); bits--) { 75 76 /* setup LSB (to slave) on leading edge */ 77 if ((flags & SPI_CONTROLLER_NO_TX) == 0) 78 setmosi(data, (word & 1)); 79 80 usleep_range(usecs, usecs + 1); /* T(setup) */ 81 82 /* sample LSB (from slave) on trailing edge */ 83 word >>= 1; 84 if ((flags & SPI_CONTROLLER_NO_RX) == 0) 85 word |= (getmiso(data) << 31); 86 87 setsck(data, !cpol); 88 usleep_range(usecs, usecs + 1); 89 90 setsck(data, cpol); 91 } 92 93 word >>= shift; 94 return word; 95 } 96 97 static int 98 spi_lp8841_rtc_transfer_one(struct spi_master *master, 99 struct spi_device *spi, 100 struct spi_transfer *t) 101 { 102 struct spi_lp8841_rtc *data = spi_master_get_devdata(master); 103 unsigned count = t->len; 104 const u8 *tx = t->tx_buf; 105 u8 *rx = t->rx_buf; 106 u8 word = 0; 107 int ret = 0; 108 109 if (tx) { 110 data->state &= ~SPI_LP8841_RTC_nWE; 111 writeb(data->state, data->iomem); 112 while (likely(count > 0)) { 113 word = *tx++; 114 bitbang_txrx_be_cpha0_lsb(data, 1, 0, 115 SPI_CONTROLLER_NO_RX, word, 8); 116 count--; 117 } 118 } else if (rx) { 119 data->state |= SPI_LP8841_RTC_nWE; 120 writeb(data->state, data->iomem); 121 while (likely(count > 0)) { 122 word = bitbang_txrx_be_cpha0_lsb(data, 1, 0, 123 SPI_CONTROLLER_NO_TX, word, 8); 124 *rx++ = word; 125 count--; 126 } 127 } else { 128 ret = -EINVAL; 129 } 130 131 spi_finalize_current_transfer(master); 132 133 return ret; 134 } 135 136 static void 137 spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable) 138 { 139 struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master); 140 141 data->state = 0; 142 writeb(data->state, data->iomem); 143 if (enable) { 144 usleep_range(4, 5); 145 data->state |= SPI_LP8841_RTC_CE; 146 writeb(data->state, data->iomem); 147 usleep_range(4, 5); 148 } 149 } 150 151 static int 152 spi_lp8841_rtc_setup(struct spi_device *spi) 153 { 154 if ((spi->mode & SPI_CS_HIGH) == 0) { 155 dev_err(&spi->dev, "unsupported active low chip select\n"); 156 return -EINVAL; 157 } 158 159 if ((spi->mode & SPI_LSB_FIRST) == 0) { 160 dev_err(&spi->dev, "unsupported MSB first mode\n"); 161 return -EINVAL; 162 } 163 164 if ((spi->mode & SPI_3WIRE) == 0) { 165 dev_err(&spi->dev, "unsupported wiring. 3 wires required\n"); 166 return -EINVAL; 167 } 168 169 return 0; 170 } 171 172 #ifdef CONFIG_OF 173 static const struct of_device_id spi_lp8841_rtc_dt_ids[] = { 174 { .compatible = "icpdas,lp8841-spi-rtc" }, 175 { } 176 }; 177 178 MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids); 179 #endif 180 181 static int 182 spi_lp8841_rtc_probe(struct platform_device *pdev) 183 { 184 int ret; 185 struct spi_master *master; 186 struct spi_lp8841_rtc *data; 187 188 master = spi_alloc_master(&pdev->dev, sizeof(*data)); 189 if (!master) 190 return -ENOMEM; 191 platform_set_drvdata(pdev, master); 192 193 master->flags = SPI_CONTROLLER_HALF_DUPLEX; 194 master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST; 195 196 master->bus_num = pdev->id; 197 master->num_chipselect = 1; 198 master->setup = spi_lp8841_rtc_setup; 199 master->set_cs = spi_lp8841_rtc_set_cs; 200 master->transfer_one = spi_lp8841_rtc_transfer_one; 201 master->bits_per_word_mask = SPI_BPW_MASK(8); 202 #ifdef CONFIG_OF 203 master->dev.of_node = pdev->dev.of_node; 204 #endif 205 206 data = spi_master_get_devdata(master); 207 208 data->iomem = devm_platform_ioremap_resource(pdev, 0); 209 ret = PTR_ERR_OR_ZERO(data->iomem); 210 if (ret) { 211 dev_err(&pdev->dev, "failed to get IO address\n"); 212 goto err_put_master; 213 } 214 215 /* register with the SPI framework */ 216 ret = devm_spi_register_master(&pdev->dev, master); 217 if (ret) { 218 dev_err(&pdev->dev, "cannot register spi master\n"); 219 goto err_put_master; 220 } 221 222 return ret; 223 224 225 err_put_master: 226 spi_master_put(master); 227 228 return ret; 229 } 230 231 MODULE_ALIAS("platform:" DRIVER_NAME); 232 233 static struct platform_driver spi_lp8841_rtc_driver = { 234 .driver = { 235 .name = DRIVER_NAME, 236 .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids), 237 }, 238 .probe = spi_lp8841_rtc_probe, 239 }; 240 module_platform_driver(spi_lp8841_rtc_driver); 241 242 MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC"); 243 MODULE_AUTHOR("Sergei Ianovich"); 244 MODULE_LICENSE("GPL"); 245