summaryrefslogtreecommitdiff
path: root/drivers/tty/serial/8250/8250_aspeed_vuart.c
blob: 0438d9a905ce979840b342f34eac5c6873f588dd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
// SPDX-License-Identifier: GPL-2.0+
/*
 *  Serial Port driver for Aspeed VUART device
 *
 *    Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp.
 *    Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.
 */
#if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/device.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/clk.h>

#include "8250.h"

#define ASPEED_VUART_GCRA		0x20
#define ASPEED_VUART_GCRA_VUART_EN		BIT(0)
#define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5)
#define ASPEED_VUART_GCRB		0x24
#define ASPEED_VUART_GCRB_HOST_SIRQ_MASK	GENMASK(7, 4)
#define ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT	4
#define ASPEED_VUART_ADDRL		0x28
#define ASPEED_VUART_ADDRH		0x2c

struct aspeed_vuart {
	struct device		*dev;
	void __iomem		*regs;
	struct clk		*clk;
	int			line;
	struct timer_list	unthrottle_timer;
	struct uart_8250_port	*port;
};

/*
 * If we fill the tty flip buffers, we throttle the data ready interrupt
 * to prevent dropped characters. This timeout defines how long we wait
 * to (conditionally, depending on buffer state) unthrottle.
 */
static const int unthrottle_timeout = HZ/10;

/*
 * The VUART is basically two UART 'front ends' connected by their FIFO
 * (no actual serial line in between). One is on the BMC side (management
 * controller) and one is on the host CPU side.
 *
 * It allows the BMC to provide to the host a "UART" that pipes into
 * the BMC itself and can then be turned by the BMC into a network console
 * of some sort for example.
 *
 * This driver is for the BMC side. The sysfs files allow the BMC
 * userspace which owns the system configuration policy, to specify
 * at what IO port and interrupt number the host side will appear
 * to the host on the Host <-> BMC LPC bus. It could be different on a
 * different system (though most of them use 3f8/4).
 */

static ssize_t lpc_address_show(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
	u16 addr;

	addr = (readb(vuart->regs + ASPEED_VUART_ADDRH) << 8) |
		(readb(vuart->regs + ASPEED_VUART_ADDRL));

	return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
}

static ssize_t lpc_address_store(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf, size_t count)
{
	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
	unsigned long val;
	int err;

	err = kstrtoul(buf, 0, &val);
	if (err)
		return err;

	writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);
	writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);

	return count;
}

static DEVICE_ATTR_RW(lpc_address);

static ssize_t sirq_show(struct device *dev,
			 struct device_attribute *attr, char *buf)
{
	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
	u8 reg;

	reg = readb(vuart->regs + ASPEED_VUART_GCRB);
	reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
	reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;

	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
}

static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,
			  const char *buf, size_t count)
{
	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
	unsigned long val;
	int err;
	u8 reg;

	err = kstrtoul(buf, 0, &val);
	if (err)
		return err;

	val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
	val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;

	reg = readb(vuart->regs + ASPEED_VUART_GCRB);
	reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
	reg |= val;
	writeb(reg, vuart->regs + ASPEED_VUART_GCRB);

	return count;
}

static DEVICE_ATTR_RW(sirq);

static struct attribute *aspeed_vuart_attrs[] = {
	&dev_attr_sirq.attr,
	&dev_attr_lpc_address.attr,
	NULL,
};

static const struct attribute_group aspeed_vuart_attr_group = {
	.attrs = aspeed_vuart_attrs,
};

static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled)
{
	u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA);

	if (enabled)
		reg |= ASPEED_VUART_GCRA_VUART_EN;
	else
		reg &= ~ASPEED_VUART_GCRA_VUART_EN;

	writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
}

static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,
					     bool discard)
{
	u8 reg;

	reg = readb(vuart->regs + ASPEED_VUART_GCRA);

	/* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */
	if (!discard)
		reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
	else
		reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;

	writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
}

static int aspeed_vuart_startup(struct uart_port *uart_port)
{
	struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
	struct aspeed_vuart *vuart = uart_8250_port->port.private_data;
	int rc;

	rc = serial8250_do_startup(uart_port);
	if (rc)
		return rc;

	aspeed_vuart_set_host_tx_discard(vuart, false);

	return 0;
}

static void aspeed_vuart_shutdown(struct uart_port *uart_port)
{
	struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
	struct aspeed_vuart *vuart = uart_8250_port->port.private_data;

	aspeed_vuart_set_host_tx_discard(vuart, true);

	serial8250_do_shutdown(uart_port);
}

static void __aspeed_vuart_set_throttle(struct uart_8250_port *up,
		bool throttle)
{
	unsigned char irqs = UART_IER_RLSI | UART_IER_RDI;

	up->ier &= ~irqs;
	if (!throttle)
		up->ier |= irqs;
	serial_out(up, UART_IER, up->ier);
}
static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle)
{
	struct uart_8250_port *up = up_to_u8250p(port);
	unsigned long flags;

	spin_lock_irqsave(&port->lock, flags);
	__aspeed_vuart_set_throttle(up, throttle);
	spin_unlock_irqrestore(&port->lock, flags);
}

static void aspeed_vuart_throttle(struct uart_port *port)
{
	aspeed_vuart_set_throttle(port, true);
}

static void aspeed_vuart_unthrottle(struct uart_port *port)
{
	aspeed_vuart_set_throttle(port, false);
}

static void aspeed_vuart_unthrottle_exp(struct timer_list *timer)
{
	struct aspeed_vuart *vuart = from_timer(vuart, timer, unthrottle_timer);
	struct uart_8250_port *up = vuart->port;

	if (!tty_buffer_space_avail(&up->port.state->port)) {
		mod_timer(&vuart->unthrottle_timer,
			  jiffies + unthrottle_timeout);
		return;
	}

	aspeed_vuart_unthrottle(&up->port);
}

/*
 * Custom interrupt handler to manage finer-grained flow control. Although we
 * have throttle/unthrottle callbacks, we've seen that the VUART device can
 * deliver characters faster than the ldisc has a chance to check buffer space
 * against the throttle threshold. This results in dropped characters before
 * the throttle.
 *
 * We do this by checking for flip buffer space before RX. If we have no space,
 * throttle now and schedule an unthrottle for later, once the ldisc has had
 * a chance to drain the buffers.
 */
static int aspeed_vuart_handle_irq(struct uart_port *port)
{
	struct uart_8250_port *up = up_to_u8250p(port);
	unsigned int iir, lsr;
	unsigned long flags;
	int space, count;

	iir = serial_port_in(port, UART_IIR);

	if (iir & UART_IIR_NO_INT)
		return 0;

	spin_lock_irqsave(&port->lock, flags);

	lsr = serial_port_in(port, UART_LSR);

	if (lsr & (UART_LSR_DR | UART_LSR_BI)) {
		space = tty_buffer_space_avail(&port->state->port);

		if (!space) {
			/* throttle and schedule an unthrottle later */
			struct aspeed_vuart *vuart = port->private_data;
			__aspeed_vuart_set_throttle(up, true);

			if (!timer_pending(&vuart->unthrottle_timer)) {
				vuart->port = up;
				mod_timer(&vuart->unthrottle_timer,
					  jiffies + unthrottle_timeout);
			}

		} else {
			count = min(space, 256);

			do {
				serial8250_read_char(up, lsr);
				lsr = serial_in(up, UART_LSR);
				if (--count == 0)
					break;
			} while (lsr & (UART_LSR_DR | UART_LSR_BI));

			tty_flip_buffer_push(&port->state->port);
		}
	}

	serial8250_modem_status(up);
	if (lsr & UART_LSR_THRE)
		serial8250_tx_chars(up);

	uart_unlock_and_check_sysrq(port, flags);

	return 1;
}

static int aspeed_vuart_probe(struct platform_device *pdev)
{
	struct uart_8250_port port;
	struct aspeed_vuart *vuart;
	struct device_node *np;
	struct resource *res;
	u32 clk, prop;
	int rc;

	np = pdev->dev.of_node;

	vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);
	if (!vuart)
		return -ENOMEM;

	vuart->dev = &pdev->dev;
	timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	vuart->regs = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(vuart->regs))
		return PTR_ERR(vuart->regs);

	memset(&port, 0, sizeof(port));
	port.port.private_data = vuart;
	port.port.membase = vuart->regs;
	port.port.mapbase = res->start;
	port.port.mapsize = resource_size(res);
	port.port.startup = aspeed_vuart_startup;
	port.port.shutdown = aspeed_vuart_shutdown;
	port.port.throttle = aspeed_vuart_throttle;
	port.port.unthrottle = aspeed_vuart_unthrottle;
	port.port.status = UPSTAT_SYNC_FIFO;
	port.port.dev = &pdev->dev;

	rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
	if (rc < 0)
		return rc;

	if (of_property_read_u32(np, "clock-frequency", &clk)) {
		vuart->clk = devm_clk_get(&pdev->dev, NULL);
		if (IS_ERR(vuart->clk)) {
			dev_warn(&pdev->dev,
				"clk or clock-frequency not defined\n");
			rc = PTR_ERR(vuart->clk);
			goto err_sysfs_remove;
		}

		rc = clk_prepare_enable(vuart->clk);
		if (rc < 0)
			goto err_sysfs_remove;

		clk = clk_get_rate(vuart->clk);
	}

	/* If current-speed was set, then try not to change it. */
	if (of_property_read_u32(np, "current-speed", &prop) == 0)
		port.port.custom_divisor = clk / (16 * prop);

	/* Check for shifted address mapping */
	if (of_property_read_u32(np, "reg-offset", &prop) == 0)
		port.port.mapbase += prop;

	/* Check for registers offset within the devices address range */
	if (of_property_read_u32(np, "reg-shift", &prop) == 0)
		port.port.regshift = prop;

	/* Check for fifo size */
	if (of_property_read_u32(np, "fifo-size", &prop) == 0)
		port.port.fifosize = prop;

	/* Check for a fixed line number */
	rc = of_alias_get_id(np, "serial");
	if (rc >= 0)
		port.port.line = rc;

	port.port.irq = irq_of_parse_and_map(np, 0);
	port.port.irqflags = IRQF_SHARED;
	port.port.handle_irq = aspeed_vuart_handle_irq;
	port.port.iotype = UPIO_MEM;
	port.port.type = PORT_16550A;
	port.port.uartclk = clk;
	port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
		| UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST;

	if (of_property_read_bool(np, "no-loopback-test"))
		port.port.flags |= UPF_SKIP_TEST;

	if (port.port.fifosize)
		port.capabilities = UART_CAP_FIFO;

	if (of_property_read_bool(np, "auto-flow-control"))
		port.capabilities |= UART_CAP_AFE;

	rc = serial8250_register_8250_port(&port);
	if (rc < 0)
		goto err_clk_disable;

	vuart->line = rc;

	aspeed_vuart_set_enabled(vuart, true);
	aspeed_vuart_set_host_tx_discard(vuart, true);
	platform_set_drvdata(pdev, vuart);

	return 0;

err_clk_disable:
	clk_disable_unprepare(vuart->clk);
	irq_dispose_mapping(port.port.irq);
err_sysfs_remove:
	sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
	return rc;
}

static int aspeed_vuart_remove(struct platform_device *pdev)
{
	struct aspeed_vuart *vuart = platform_get_drvdata(pdev);

	del_timer_sync(&vuart->unthrottle_timer);
	aspeed_vuart_set_enabled(vuart, false);
	serial8250_unregister_port(vuart->line);
	sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
	clk_disable_unprepare(vuart->clk);

	return 0;
}

static const struct of_device_id aspeed_vuart_table[] = {
	{ .compatible = "aspeed,ast2400-vuart" },
	{ .compatible = "aspeed,ast2500-vuart" },
	{ },
};

static struct platform_driver aspeed_vuart_driver = {
	.driver = {
		.name = "aspeed-vuart",
		.of_match_table = aspeed_vuart_table,
	},
	.probe = aspeed_vuart_probe,
	.remove = aspeed_vuart_remove,
};

module_platform_driver(aspeed_vuart_driver);

MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Driver for Aspeed VUART device");