1 /* 2 * Support for Serial I/O using STMicroelectronics' on-chip ASC. 3 * 4 * Copyright (c) 2017 5 * Patrice Chotard <patrice.chotard@st.com> 6 * 7 * SPDX-License-Identifier: GPL-2.0 8 */ 9 10 #include <common.h> 11 #include <dm.h> 12 #include <serial.h> 13 #include <asm/io.h> 14 15 DECLARE_GLOBAL_DATA_PTR; 16 17 #define BAUDMODE 0x00001000 18 #define RXENABLE 0x00000100 19 #define RUN 0x00000080 20 #define MODE 0x00000001 21 #define MODE_8BIT 0x0001 22 #define STOP_1BIT 0x0008 23 #define PARITYODD 0x0020 24 25 #define STA_TF BIT(9) 26 #define STA_RBF BIT(0) 27 28 struct sti_asc_uart { 29 u32 baudrate; 30 u32 txbuf; 31 u32 rxbuf; 32 u32 control; 33 u32 inten; 34 u32 status; 35 u32 guardtime; 36 u32 timeout; 37 u32 txreset; 38 u32 rxreset; 39 }; 40 41 struct sti_asc_serial { 42 /* address of registers in physical memory */ 43 struct sti_asc_uart *regs; 44 }; 45 46 /* Values for the BAUDRATE Register */ 47 #define PCLK (200ul * 1000000ul) 48 #define BAUDRATE_VAL_M0(bps) (PCLK / (16 * (bps))) 49 #define BAUDRATE_VAL_M1(bps) ((bps * (1 << 14)) + (1<<13)) / (PCLK/(1 << 6)) 50 51 /* 52 * MODE 0 53 * ICCLK 54 * ASCBaudRate = ---------------- 55 * baudrate * 16 56 * 57 * MODE 1 58 * baudrate * 16 * 2^16 59 * ASCBaudRate = ------------------------ 60 * ICCLK 61 * 62 * NOTE: 63 * Mode 1 should be used for baudrates of 19200, and above, as it 64 * has a lower deviation error than Mode 0 for higher frequencies. 65 * Mode 0 should be used for all baudrates below 19200. 66 */ 67 68 static int sti_asc_pending(struct udevice *dev, bool input) 69 { 70 struct sti_asc_serial *priv = dev_get_priv(dev); 71 struct sti_asc_uart *const uart = priv->regs; 72 unsigned long status; 73 74 status = readl(&uart->status); 75 if (input) 76 return status & STA_RBF; 77 else 78 return status & STA_TF; 79 } 80 81 static int _sti_asc_serial_setbrg(struct sti_asc_uart *uart, int baudrate) 82 { 83 unsigned long val; 84 int t, mode = 1; 85 86 switch (baudrate) { 87 case 9600: 88 t = BAUDRATE_VAL_M0(9600); 89 mode = 0; 90 break; 91 case 19200: 92 t = BAUDRATE_VAL_M1(19200); 93 break; 94 case 38400: 95 t = BAUDRATE_VAL_M1(38400); 96 break; 97 case 57600: 98 t = BAUDRATE_VAL_M1(57600); 99 break; 100 default: 101 debug("ASC: unsupported baud rate: %d, using 115200 instead.\n", 102 baudrate); 103 case 115200: 104 t = BAUDRATE_VAL_M1(115200); 105 break; 106 } 107 108 /* disable the baudrate generator */ 109 val = readl(&uart->control); 110 writel(val & ~RUN, &uart->control); 111 112 /* set baud generator reload value */ 113 writel(t, &uart->baudrate); 114 /* reset the RX & TX buffers */ 115 writel(1, &uart->txreset); 116 writel(1, &uart->rxreset); 117 118 /* set baud generator mode */ 119 if (mode) 120 val |= BAUDMODE; 121 122 /* finally, write value and enable ASC */ 123 writel(val, &uart->control); 124 125 return 0; 126 } 127 128 /* called to adjust baud-rate */ 129 static int sti_asc_serial_setbrg(struct udevice *dev, int baudrate) 130 { 131 struct sti_asc_serial *priv = dev_get_priv(dev); 132 struct sti_asc_uart *const uart = priv->regs; 133 134 return _sti_asc_serial_setbrg(uart, baudrate); 135 } 136 137 /* blocking function, that returns next char */ 138 static int sti_asc_serial_getc(struct udevice *dev) 139 { 140 struct sti_asc_serial *priv = dev_get_priv(dev); 141 struct sti_asc_uart *const uart = priv->regs; 142 143 /* polling wait: for a char to be read */ 144 if (!sti_asc_pending(dev, true)) 145 return -EAGAIN; 146 147 return readl(&uart->rxbuf); 148 } 149 150 /* write write out a single char */ 151 static int sti_asc_serial_putc(struct udevice *dev, const char c) 152 { 153 struct sti_asc_serial *priv = dev_get_priv(dev); 154 struct sti_asc_uart *const uart = priv->regs; 155 156 /* wait till safe to write next char */ 157 if (sti_asc_pending(dev, false)) 158 return -EAGAIN; 159 160 /* finally, write next char */ 161 writel(c, &uart->txbuf); 162 163 return 0; 164 } 165 166 /* initialize the ASC */ 167 static int sti_asc_serial_probe(struct udevice *dev) 168 { 169 struct sti_asc_serial *priv = dev_get_priv(dev); 170 unsigned long val; 171 fdt_addr_t base; 172 173 base = dev_get_addr(dev); 174 if (base == FDT_ADDR_T_NONE) 175 return -EINVAL; 176 177 priv->regs = (struct sti_asc_uart *)base; 178 sti_asc_serial_setbrg(dev, gd->baudrate); 179 180 /* 181 * build up the value to be written to CONTROL 182 * set character length, bit stop number, odd parity 183 */ 184 val = RXENABLE | RUN | MODE_8BIT | STOP_1BIT | PARITYODD; 185 writel(val, &priv->regs->control); 186 187 return 0; 188 } 189 190 static const struct dm_serial_ops sti_asc_serial_ops = { 191 .putc = sti_asc_serial_putc, 192 .pending = sti_asc_pending, 193 .getc = sti_asc_serial_getc, 194 .setbrg = sti_asc_serial_setbrg, 195 }; 196 197 static const struct udevice_id sti_serial_of_match[] = { 198 { .compatible = "st,asc" }, 199 { } 200 }; 201 202 U_BOOT_DRIVER(serial_sti_asc) = { 203 .name = "serial_sti_asc", 204 .id = UCLASS_SERIAL, 205 .of_match = sti_serial_of_match, 206 .ops = &sti_asc_serial_ops, 207 .probe = sti_asc_serial_probe, 208 .priv_auto_alloc_size = sizeof(struct sti_asc_serial), 209 .flags = DM_FLAG_PRE_RELOC, 210 }; 211 212