1 // SPDX-License-Identifier: GPL-2.0+
2 /* Synopsys DesignWare 8250 library. */
3 
4 #include <linux/bitops.h>
5 #include <linux/bitfield.h>
6 #include <linux/delay.h>
7 #include <linux/device.h>
8 #include <linux/kernel.h>
9 #include <linux/math.h>
10 #include <linux/property.h>
11 #include <linux/serial_8250.h>
12 #include <linux/serial_core.h>
13 
14 #include "8250_dwlib.h"
15 
16 /* Offsets for the DesignWare specific registers */
17 #define DW_UART_TCR	0xac /* Transceiver Control Register (RS485) */
18 #define DW_UART_DE_EN	0xb0 /* Driver Output Enable Register */
19 #define DW_UART_RE_EN	0xb4 /* Receiver Output Enable Register */
20 #define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
21 #define DW_UART_RAR	0xc4 /* Receive Address Register */
22 #define DW_UART_TAR	0xc8 /* Transmit Address Register */
23 #define DW_UART_LCR_EXT	0xcc /* Line Extended Control Register */
24 #define DW_UART_CPR	0xf4 /* Component Parameter Register */
25 #define DW_UART_UCV	0xf8 /* UART Component Version */
26 
27 /* Receive / Transmit Address Register bits */
28 #define DW_UART_ADDR_MASK		GENMASK(7, 0)
29 
30 /* Line Status Register bits */
31 #define DW_UART_LSR_ADDR_RCVD		BIT(8)
32 
33 /* Transceiver Control Register bits */
34 #define DW_UART_TCR_RS485_EN		BIT(0)
35 #define DW_UART_TCR_RE_POL		BIT(1)
36 #define DW_UART_TCR_DE_POL		BIT(2)
37 #define DW_UART_TCR_XFER_MODE		GENMASK(4, 3)
38 #define DW_UART_TCR_XFER_MODE_DE_DURING_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 0)
39 #define DW_UART_TCR_XFER_MODE_SW_DE_OR_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 1)
40 #define DW_UART_TCR_XFER_MODE_DE_OR_RE		FIELD_PREP(DW_UART_TCR_XFER_MODE, 2)
41 
42 /* Line Extended Control Register bits */
43 #define DW_UART_LCR_EXT_DLS_E		BIT(0)
44 #define DW_UART_LCR_EXT_ADDR_MATCH	BIT(1)
45 #define DW_UART_LCR_EXT_SEND_ADDR	BIT(2)
46 #define DW_UART_LCR_EXT_TRANSMIT_MODE	BIT(3)
47 
48 /* Component Parameter Register bits */
49 #define DW_UART_CPR_ABP_DATA_WIDTH	GENMASK(1, 0)
50 #define DW_UART_CPR_AFCE_MODE		BIT(4)
51 #define DW_UART_CPR_THRE_MODE		BIT(5)
52 #define DW_UART_CPR_SIR_MODE		BIT(6)
53 #define DW_UART_CPR_SIR_LP_MODE		BIT(7)
54 #define DW_UART_CPR_ADDITIONAL_FEATURES	BIT(8)
55 #define DW_UART_CPR_FIFO_ACCESS		BIT(9)
56 #define DW_UART_CPR_FIFO_STAT		BIT(10)
57 #define DW_UART_CPR_SHADOW		BIT(11)
58 #define DW_UART_CPR_ENCODED_PARMS	BIT(12)
59 #define DW_UART_CPR_DMA_EXTRA		BIT(13)
60 #define DW_UART_CPR_FIFO_MODE		GENMASK(23, 16)
61 
62 /* Helper for FIFO size calculation */
63 #define DW_UART_CPR_FIFO_SIZE(a)	(FIELD_GET(DW_UART_CPR_FIFO_MODE, (a)) * 16)
64 
65 /*
66  * divisor = div(I) + div(F)
67  * "I" means integer, "F" means fractional
68  * quot = div(I) = clk / (16 * baud)
69  * frac = div(F) * 2^dlf_size
70  *
71  * let rem = clk % (16 * baud)
72  * we have: div(F) * (16 * baud) = rem
73  * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) / (16 * baud)
74  */
75 static unsigned int dw8250_get_divisor(struct uart_port *p, unsigned int baud,
76 				       unsigned int *frac)
77 {
78 	unsigned int quot, rem, base_baud = baud * 16;
79 	struct dw8250_port_data *d = p->private_data;
80 
81 	quot = p->uartclk / base_baud;
82 	rem = p->uartclk % base_baud;
83 	*frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, base_baud);
84 
85 	return quot;
86 }
87 
88 static void dw8250_set_divisor(struct uart_port *p, unsigned int baud,
89 			       unsigned int quot, unsigned int quot_frac)
90 {
91 	dw8250_writel_ext(p, DW_UART_DLF, quot_frac);
92 	serial8250_do_set_divisor(p, baud, quot, quot_frac);
93 }
94 
95 void dw8250_do_set_termios(struct uart_port *p, struct ktermios *termios,
96 			   const struct ktermios *old)
97 {
98 	p->status &= ~UPSTAT_AUTOCTS;
99 	if (termios->c_cflag & CRTSCTS)
100 		p->status |= UPSTAT_AUTOCTS;
101 
102 	serial8250_do_set_termios(p, termios, old);
103 
104 	/* Filter addresses which have 9th bit set */
105 	p->ignore_status_mask |= DW_UART_LSR_ADDR_RCVD;
106 	p->read_status_mask |= DW_UART_LSR_ADDR_RCVD;
107 }
108 EXPORT_SYMBOL_GPL(dw8250_do_set_termios);
109 
110 /*
111  * Wait until re is de-asserted for sure. An ongoing receive will keep
112  * re asserted until end of frame. Without BUSY indication available,
113  * only available course of action is to wait for the time it takes to
114  * receive one frame (there might nothing to receive but w/o BUSY the
115  * driver cannot know).
116  */
117 static void dw8250_wait_re_deassert(struct uart_port *p)
118 {
119 	ndelay(p->frame_time);
120 }
121 
122 static void dw8250_update_rar(struct uart_port *p, u32 addr)
123 {
124 	u32 re_en = dw8250_readl_ext(p, DW_UART_RE_EN);
125 
126 	/*
127 	 * RAR shouldn't be changed while receiving. Thus, de-assert RE_EN
128 	 * if asserted and wait.
129 	 */
130 	if (re_en)
131 		dw8250_writel_ext(p, DW_UART_RE_EN, 0);
132 	dw8250_wait_re_deassert(p);
133 	dw8250_writel_ext(p, DW_UART_RAR, addr);
134 	if (re_en)
135 		dw8250_writel_ext(p, DW_UART_RE_EN, re_en);
136 }
137 
138 static void dw8250_rs485_set_addr(struct uart_port *p, struct serial_rs485 *rs485,
139 				  struct ktermios *termios)
140 {
141 	u32 lcr = dw8250_readl_ext(p, DW_UART_LCR_EXT);
142 
143 	if (rs485->flags & SER_RS485_ADDRB) {
144 		lcr |= DW_UART_LCR_EXT_DLS_E;
145 		if (termios)
146 			termios->c_cflag |= ADDRB;
147 
148 		if (rs485->flags & SER_RS485_ADDR_RECV) {
149 			u32 delta = p->rs485.flags ^ rs485->flags;
150 
151 			/*
152 			 * rs485 (param) is equal to uart_port's rs485 only during init
153 			 * (during init, delta is not yet applicable).
154 			 */
155 			if (unlikely(&p->rs485 == rs485))
156 				delta = rs485->flags;
157 
158 			if ((delta & SER_RS485_ADDR_RECV) ||
159 			    (p->rs485.addr_recv != rs485->addr_recv))
160 				dw8250_update_rar(p, rs485->addr_recv);
161 			lcr |= DW_UART_LCR_EXT_ADDR_MATCH;
162 		} else {
163 			lcr &= ~DW_UART_LCR_EXT_ADDR_MATCH;
164 		}
165 		if (rs485->flags & SER_RS485_ADDR_DEST) {
166 			/*
167 			 * Don't skip writes here as another endpoint could
168 			 * have changed communication line's destination
169 			 * address in between.
170 			 */
171 			dw8250_writel_ext(p, DW_UART_TAR, rs485->addr_dest);
172 			lcr |= DW_UART_LCR_EXT_SEND_ADDR;
173 		}
174 	} else {
175 		lcr = 0;
176 	}
177 	dw8250_writel_ext(p, DW_UART_LCR_EXT, lcr);
178 }
179 
180 static int dw8250_rs485_config(struct uart_port *p, struct ktermios *termios,
181 			       struct serial_rs485 *rs485)
182 {
183 	u32 tcr;
184 
185 	tcr = dw8250_readl_ext(p, DW_UART_TCR);
186 	tcr &= ~DW_UART_TCR_XFER_MODE;
187 
188 	if (rs485->flags & SER_RS485_ENABLED) {
189 		tcr |= DW_UART_TCR_RS485_EN;
190 
191 		if (rs485->flags & SER_RS485_RX_DURING_TX)
192 			tcr |= DW_UART_TCR_XFER_MODE_DE_DURING_RE;
193 		else
194 			tcr |= DW_UART_TCR_XFER_MODE_DE_OR_RE;
195 		dw8250_writel_ext(p, DW_UART_DE_EN, 1);
196 		dw8250_writel_ext(p, DW_UART_RE_EN, 1);
197 	} else {
198 		if (termios)
199 			termios->c_cflag &= ~ADDRB;
200 
201 		tcr &= ~DW_UART_TCR_RS485_EN;
202 	}
203 
204 	/* Reset to default polarity */
205 	tcr |= DW_UART_TCR_DE_POL;
206 	tcr &= ~DW_UART_TCR_RE_POL;
207 
208 	if (!(rs485->flags & SER_RS485_RTS_ON_SEND))
209 		tcr &= ~DW_UART_TCR_DE_POL;
210 	if (device_property_read_bool(p->dev, "rs485-rx-active-high"))
211 		tcr |= DW_UART_TCR_RE_POL;
212 
213 	dw8250_writel_ext(p, DW_UART_TCR, tcr);
214 
215 	/* Addressing mode can only be set up after TCR */
216 	if (rs485->flags & SER_RS485_ENABLED)
217 		dw8250_rs485_set_addr(p, rs485, termios);
218 
219 	return 0;
220 }
221 
222 /*
223  * Tests if RE_EN register can have non-zero value to see if RS-485 HW support
224  * is present.
225  */
226 static bool dw8250_detect_rs485_hw(struct uart_port *p)
227 {
228 	u32 reg;
229 
230 	dw8250_writel_ext(p, DW_UART_RE_EN, 1);
231 	reg = dw8250_readl_ext(p, DW_UART_RE_EN);
232 	dw8250_writel_ext(p, DW_UART_RE_EN, 0);
233 	return reg;
234 }
235 
236 static const struct serial_rs485 dw8250_rs485_supported = {
237 	.flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_RTS_ON_SEND |
238 		 SER_RS485_RTS_AFTER_SEND | SER_RS485_ADDRB | SER_RS485_ADDR_RECV |
239 		 SER_RS485_ADDR_DEST,
240 };
241 
242 void dw8250_setup_port(struct uart_port *p)
243 {
244 	struct dw8250_port_data *pd = p->private_data;
245 	struct uart_8250_port *up = up_to_u8250p(p);
246 	u32 reg, old_dlf;
247 
248 	pd->hw_rs485_support = dw8250_detect_rs485_hw(p);
249 	if (pd->hw_rs485_support) {
250 		p->rs485_config = dw8250_rs485_config;
251 		up->lsr_save_mask = LSR_SAVE_FLAGS | DW_UART_LSR_ADDR_RCVD;
252 		p->rs485_supported = dw8250_rs485_supported;
253 	} else {
254 		p->rs485_config = serial8250_em485_config;
255 		p->rs485_supported = serial8250_em485_supported;
256 		up->rs485_start_tx = serial8250_em485_start_tx;
257 		up->rs485_stop_tx = serial8250_em485_stop_tx;
258 	}
259 	up->capabilities |= UART_CAP_NOTEMT;
260 
261 	/*
262 	 * If the Component Version Register returns zero, we know that
263 	 * ADDITIONAL_FEATURES are not enabled. No need to go any further.
264 	 */
265 	reg = dw8250_readl_ext(p, DW_UART_UCV);
266 	if (!reg)
267 		return;
268 
269 	dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
270 		(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
271 
272 	/* Preserve value written by firmware or bootloader  */
273 	old_dlf = dw8250_readl_ext(p, DW_UART_DLF);
274 	dw8250_writel_ext(p, DW_UART_DLF, ~0U);
275 	reg = dw8250_readl_ext(p, DW_UART_DLF);
276 	dw8250_writel_ext(p, DW_UART_DLF, old_dlf);
277 
278 	if (reg) {
279 		pd->dlf_size = fls(reg);
280 		p->get_divisor = dw8250_get_divisor;
281 		p->set_divisor = dw8250_set_divisor;
282 	}
283 
284 	reg = dw8250_readl_ext(p, DW_UART_CPR);
285 	if (!reg) {
286 		reg = pd->cpr_value;
287 		dev_dbg(p->dev, "CPR is not available, using 0x%08x instead\n", reg);
288 	}
289 	if (!reg)
290 		return;
291 
292 	/* Select the type based on FIFO */
293 	if (reg & DW_UART_CPR_FIFO_MODE) {
294 		p->type = PORT_16550A;
295 		p->flags |= UPF_FIXED_TYPE;
296 		p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
297 		up->capabilities = UART_CAP_FIFO | UART_CAP_NOTEMT;
298 	}
299 
300 	if (reg & DW_UART_CPR_AFCE_MODE)
301 		up->capabilities |= UART_CAP_AFE;
302 
303 	if (reg & DW_UART_CPR_SIR_MODE)
304 		up->capabilities |= UART_CAP_IRDA;
305 }
306 EXPORT_SYMBOL_GPL(dw8250_setup_port);
307