1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Serial Port driver for Aspeed VUART device
4 *
5 * Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp.
6 * Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.
7 */
8 #if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
9 #define SUPPORT_SYSRQ
10 #endif
11
12 #include <linux/device.h>
13 #include <linux/module.h>
14 #include <linux/of_address.h>
15 #include <linux/of_irq.h>
16 #include <linux/of_platform.h>
17 #include <linux/tty.h>
18 #include <linux/tty_flip.h>
19 #include <linux/clk.h>
20
21 #include "8250.h"
22
23 #define ASPEED_VUART_GCRA 0x20
24 #define ASPEED_VUART_GCRA_VUART_EN BIT(0)
25 #define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5)
26 #define ASPEED_VUART_GCRB 0x24
27 #define ASPEED_VUART_GCRB_HOST_SIRQ_MASK GENMASK(7, 4)
28 #define ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT 4
29 #define ASPEED_VUART_ADDRL 0x28
30 #define ASPEED_VUART_ADDRH 0x2c
31
32 struct aspeed_vuart {
33 struct device *dev;
34 void __iomem *regs;
35 struct clk *clk;
36 int line;
37 struct timer_list unthrottle_timer;
38 struct uart_8250_port *port;
39 };
40
41 /*
42 * If we fill the tty flip buffers, we throttle the data ready interrupt
43 * to prevent dropped characters. This timeout defines how long we wait
44 * to (conditionally, depending on buffer state) unthrottle.
45 */
46 static const int unthrottle_timeout = HZ/10;
47
48 /*
49 * The VUART is basically two UART 'front ends' connected by their FIFO
50 * (no actual serial line in between). One is on the BMC side (management
51 * controller) and one is on the host CPU side.
52 *
53 * It allows the BMC to provide to the host a "UART" that pipes into
54 * the BMC itself and can then be turned by the BMC into a network console
55 * of some sort for example.
56 *
57 * This driver is for the BMC side. The sysfs files allow the BMC
58 * userspace which owns the system configuration policy, to specify
59 * at what IO port and interrupt number the host side will appear
60 * to the host on the Host <-> BMC LPC bus. It could be different on a
61 * different system (though most of them use 3f8/4).
62 */
63
lpc_address_show(struct device * dev,struct device_attribute * attr,char * buf)64 static ssize_t lpc_address_show(struct device *dev,
65 struct device_attribute *attr, char *buf)
66 {
67 struct aspeed_vuart *vuart = dev_get_drvdata(dev);
68 u16 addr;
69
70 addr = (readb(vuart->regs + ASPEED_VUART_ADDRH) << 8) |
71 (readb(vuart->regs + ASPEED_VUART_ADDRL));
72
73 return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
74 }
75
lpc_address_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)76 static ssize_t lpc_address_store(struct device *dev,
77 struct device_attribute *attr,
78 const char *buf, size_t count)
79 {
80 struct aspeed_vuart *vuart = dev_get_drvdata(dev);
81 unsigned long val;
82 int err;
83
84 err = kstrtoul(buf, 0, &val);
85 if (err)
86 return err;
87
88 writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);
89 writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);
90
91 return count;
92 }
93
94 static DEVICE_ATTR_RW(lpc_address);
95
sirq_show(struct device * dev,struct device_attribute * attr,char * buf)96 static ssize_t sirq_show(struct device *dev,
97 struct device_attribute *attr, char *buf)
98 {
99 struct aspeed_vuart *vuart = dev_get_drvdata(dev);
100 u8 reg;
101
102 reg = readb(vuart->regs + ASPEED_VUART_GCRB);
103 reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
104 reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
105
106 return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
107 }
108
sirq_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)109 static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,
110 const char *buf, size_t count)
111 {
112 struct aspeed_vuart *vuart = dev_get_drvdata(dev);
113 unsigned long val;
114 int err;
115 u8 reg;
116
117 err = kstrtoul(buf, 0, &val);
118 if (err)
119 return err;
120
121 val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
122 val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
123
124 reg = readb(vuart->regs + ASPEED_VUART_GCRB);
125 reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
126 reg |= val;
127 writeb(reg, vuart->regs + ASPEED_VUART_GCRB);
128
129 return count;
130 }
131
132 static DEVICE_ATTR_RW(sirq);
133
134 static struct attribute *aspeed_vuart_attrs[] = {
135 &dev_attr_sirq.attr,
136 &dev_attr_lpc_address.attr,
137 NULL,
138 };
139
140 static const struct attribute_group aspeed_vuart_attr_group = {
141 .attrs = aspeed_vuart_attrs,
142 };
143
aspeed_vuart_set_enabled(struct aspeed_vuart * vuart,bool enabled)144 static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled)
145 {
146 u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA);
147
148 if (enabled)
149 reg |= ASPEED_VUART_GCRA_VUART_EN;
150 else
151 reg &= ~ASPEED_VUART_GCRA_VUART_EN;
152
153 writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
154 }
155
aspeed_vuart_set_host_tx_discard(struct aspeed_vuart * vuart,bool discard)156 static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,
157 bool discard)
158 {
159 u8 reg;
160
161 reg = readb(vuart->regs + ASPEED_VUART_GCRA);
162
163 /* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */
164 if (!discard)
165 reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
166 else
167 reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
168
169 writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
170 }
171
aspeed_vuart_startup(struct uart_port * uart_port)172 static int aspeed_vuart_startup(struct uart_port *uart_port)
173 {
174 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
175 struct aspeed_vuart *vuart = uart_8250_port->port.private_data;
176 int rc;
177
178 rc = serial8250_do_startup(uart_port);
179 if (rc)
180 return rc;
181
182 aspeed_vuart_set_host_tx_discard(vuart, false);
183
184 return 0;
185 }
186
aspeed_vuart_shutdown(struct uart_port * uart_port)187 static void aspeed_vuart_shutdown(struct uart_port *uart_port)
188 {
189 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
190 struct aspeed_vuart *vuart = uart_8250_port->port.private_data;
191
192 aspeed_vuart_set_host_tx_discard(vuart, true);
193
194 serial8250_do_shutdown(uart_port);
195 }
196
__aspeed_vuart_set_throttle(struct uart_8250_port * up,bool throttle)197 static void __aspeed_vuart_set_throttle(struct uart_8250_port *up,
198 bool throttle)
199 {
200 unsigned char irqs = UART_IER_RLSI | UART_IER_RDI;
201
202 up->ier &= ~irqs;
203 if (!throttle)
204 up->ier |= irqs;
205 serial_out(up, UART_IER, up->ier);
206 }
aspeed_vuart_set_throttle(struct uart_port * port,bool throttle)207 static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle)
208 {
209 struct uart_8250_port *up = up_to_u8250p(port);
210 unsigned long flags;
211
212 spin_lock_irqsave(&port->lock, flags);
213 __aspeed_vuart_set_throttle(up, throttle);
214 spin_unlock_irqrestore(&port->lock, flags);
215 }
216
aspeed_vuart_throttle(struct uart_port * port)217 static void aspeed_vuart_throttle(struct uart_port *port)
218 {
219 aspeed_vuart_set_throttle(port, true);
220 }
221
aspeed_vuart_unthrottle(struct uart_port * port)222 static void aspeed_vuart_unthrottle(struct uart_port *port)
223 {
224 aspeed_vuart_set_throttle(port, false);
225 }
226
aspeed_vuart_unthrottle_exp(struct timer_list * timer)227 static void aspeed_vuart_unthrottle_exp(struct timer_list *timer)
228 {
229 struct aspeed_vuart *vuart = from_timer(vuart, timer, unthrottle_timer);
230 struct uart_8250_port *up = vuart->port;
231
232 if (!tty_buffer_space_avail(&up->port.state->port)) {
233 mod_timer(&vuart->unthrottle_timer,
234 jiffies + unthrottle_timeout);
235 return;
236 }
237
238 aspeed_vuart_unthrottle(&up->port);
239 }
240
241 /*
242 * Custom interrupt handler to manage finer-grained flow control. Although we
243 * have throttle/unthrottle callbacks, we've seen that the VUART device can
244 * deliver characters faster than the ldisc has a chance to check buffer space
245 * against the throttle threshold. This results in dropped characters before
246 * the throttle.
247 *
248 * We do this by checking for flip buffer space before RX. If we have no space,
249 * throttle now and schedule an unthrottle for later, once the ldisc has had
250 * a chance to drain the buffers.
251 */
aspeed_vuart_handle_irq(struct uart_port * port)252 static int aspeed_vuart_handle_irq(struct uart_port *port)
253 {
254 struct uart_8250_port *up = up_to_u8250p(port);
255 unsigned int iir, lsr;
256 unsigned long flags;
257 int space, count;
258
259 iir = serial_port_in(port, UART_IIR);
260
261 if (iir & UART_IIR_NO_INT)
262 return 0;
263
264 spin_lock_irqsave(&port->lock, flags);
265
266 lsr = serial_port_in(port, UART_LSR);
267
268 if (lsr & (UART_LSR_DR | UART_LSR_BI)) {
269 space = tty_buffer_space_avail(&port->state->port);
270
271 if (!space) {
272 /* throttle and schedule an unthrottle later */
273 struct aspeed_vuart *vuart = port->private_data;
274 __aspeed_vuart_set_throttle(up, true);
275
276 if (!timer_pending(&vuart->unthrottle_timer)) {
277 vuart->port = up;
278 mod_timer(&vuart->unthrottle_timer,
279 jiffies + unthrottle_timeout);
280 }
281
282 } else {
283 count = min(space, 256);
284
285 do {
286 serial8250_read_char(up, lsr);
287 lsr = serial_in(up, UART_LSR);
288 if (--count == 0)
289 break;
290 } while (lsr & (UART_LSR_DR | UART_LSR_BI));
291
292 tty_flip_buffer_push(&port->state->port);
293 }
294 }
295
296 serial8250_modem_status(up);
297 if (lsr & UART_LSR_THRE)
298 serial8250_tx_chars(up);
299
300 uart_unlock_and_check_sysrq(port, flags);
301
302 return 1;
303 }
304
aspeed_vuart_probe(struct platform_device * pdev)305 static int aspeed_vuart_probe(struct platform_device *pdev)
306 {
307 struct uart_8250_port port;
308 struct aspeed_vuart *vuart;
309 struct device_node *np;
310 struct resource *res;
311 u32 clk, prop;
312 int rc;
313
314 np = pdev->dev.of_node;
315
316 vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);
317 if (!vuart)
318 return -ENOMEM;
319
320 vuart->dev = &pdev->dev;
321 timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0);
322
323 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
324 vuart->regs = devm_ioremap_resource(&pdev->dev, res);
325 if (IS_ERR(vuart->regs))
326 return PTR_ERR(vuart->regs);
327
328 memset(&port, 0, sizeof(port));
329 port.port.private_data = vuart;
330 port.port.membase = vuart->regs;
331 port.port.mapbase = res->start;
332 port.port.mapsize = resource_size(res);
333 port.port.startup = aspeed_vuart_startup;
334 port.port.shutdown = aspeed_vuart_shutdown;
335 port.port.throttle = aspeed_vuart_throttle;
336 port.port.unthrottle = aspeed_vuart_unthrottle;
337 port.port.status = UPSTAT_SYNC_FIFO;
338 port.port.dev = &pdev->dev;
339
340 rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
341 if (rc < 0)
342 return rc;
343
344 if (of_property_read_u32(np, "clock-frequency", &clk)) {
345 vuart->clk = devm_clk_get(&pdev->dev, NULL);
346 if (IS_ERR(vuart->clk)) {
347 dev_warn(&pdev->dev,
348 "clk or clock-frequency not defined\n");
349 rc = PTR_ERR(vuart->clk);
350 goto err_sysfs_remove;
351 }
352
353 rc = clk_prepare_enable(vuart->clk);
354 if (rc < 0)
355 goto err_sysfs_remove;
356
357 clk = clk_get_rate(vuart->clk);
358 }
359
360 /* If current-speed was set, then try not to change it. */
361 if (of_property_read_u32(np, "current-speed", &prop) == 0)
362 port.port.custom_divisor = clk / (16 * prop);
363
364 /* Check for shifted address mapping */
365 if (of_property_read_u32(np, "reg-offset", &prop) == 0)
366 port.port.mapbase += prop;
367
368 /* Check for registers offset within the devices address range */
369 if (of_property_read_u32(np, "reg-shift", &prop) == 0)
370 port.port.regshift = prop;
371
372 /* Check for fifo size */
373 if (of_property_read_u32(np, "fifo-size", &prop) == 0)
374 port.port.fifosize = prop;
375
376 /* Check for a fixed line number */
377 rc = of_alias_get_id(np, "serial");
378 if (rc >= 0)
379 port.port.line = rc;
380
381 port.port.irq = irq_of_parse_and_map(np, 0);
382 port.port.irqflags = IRQF_SHARED;
383 port.port.handle_irq = aspeed_vuart_handle_irq;
384 port.port.iotype = UPIO_MEM;
385 port.port.type = PORT_16550A;
386 port.port.uartclk = clk;
387 port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
388 | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST;
389
390 if (of_property_read_bool(np, "no-loopback-test"))
391 port.port.flags |= UPF_SKIP_TEST;
392
393 if (port.port.fifosize)
394 port.capabilities = UART_CAP_FIFO;
395
396 if (of_property_read_bool(np, "auto-flow-control"))
397 port.capabilities |= UART_CAP_AFE;
398
399 rc = serial8250_register_8250_port(&port);
400 if (rc < 0)
401 goto err_clk_disable;
402
403 vuart->line = rc;
404
405 aspeed_vuart_set_enabled(vuart, true);
406 aspeed_vuart_set_host_tx_discard(vuart, true);
407 platform_set_drvdata(pdev, vuart);
408
409 return 0;
410
411 err_clk_disable:
412 clk_disable_unprepare(vuart->clk);
413 irq_dispose_mapping(port.port.irq);
414 err_sysfs_remove:
415 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
416 return rc;
417 }
418
aspeed_vuart_remove(struct platform_device * pdev)419 static int aspeed_vuart_remove(struct platform_device *pdev)
420 {
421 struct aspeed_vuart *vuart = platform_get_drvdata(pdev);
422
423 del_timer_sync(&vuart->unthrottle_timer);
424 aspeed_vuart_set_enabled(vuart, false);
425 serial8250_unregister_port(vuart->line);
426 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
427 clk_disable_unprepare(vuart->clk);
428
429 return 0;
430 }
431
432 static const struct of_device_id aspeed_vuart_table[] = {
433 { .compatible = "aspeed,ast2400-vuart" },
434 { .compatible = "aspeed,ast2500-vuart" },
435 { },
436 };
437
438 static struct platform_driver aspeed_vuart_driver = {
439 .driver = {
440 .name = "aspeed-vuart",
441 .of_match_table = aspeed_vuart_table,
442 },
443 .probe = aspeed_vuart_probe,
444 .remove = aspeed_vuart_remove,
445 };
446
447 module_platform_driver(aspeed_vuart_driver);
448
449 MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>");
450 MODULE_LICENSE("GPL");
451 MODULE_DESCRIPTION("Driver for Aspeed VUART device");
452
