1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
4 *
5 * Derived from pl01x code:
6 *
7 * (C) Copyright 2000
8 * Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
9 *
10 * (C) Copyright 2004
11 * ARM Ltd.
12 * Philippe Robin, <philippe.robin@arm.com>
13 */
14
15/* Simple U-Boot driver for the BCM283x mini UART */
16
17#include <common.h>
18#include <dm.h>
19#include <errno.h>
20#include <watchdog.h>
21#include <asm/gpio.h>
22#include <asm/io.h>
23#include <serial.h>
24#include <dm/platform_data/serial_bcm283x_mu.h>
25#include <dm/pinctrl.h>
26#include <linux/bitops.h>
27#include <linux/compiler.h>
28
29struct bcm283x_mu_regs {
30	u32 io;
31	u32 iir;
32	u32 ier;
33	u32 lcr;
34	u32 mcr;
35	u32 lsr;
36	u32 msr;
37	u32 scratch;
38	u32 cntl;
39	u32 stat;
40	u32 baud;
41};
42
43#define BCM283X_MU_LCR_DATA_SIZE_8	3
44
45#define BCM283X_MU_LSR_TX_IDLE		BIT(6)
46/* This actually means not full, but is named not empty in the docs */
47#define BCM283X_MU_LSR_TX_EMPTY		BIT(5)
48#define BCM283X_MU_LSR_RX_READY		BIT(0)
49
50struct bcm283x_mu_priv {
51	struct bcm283x_mu_regs *regs;
52};
53
54static int bcm283x_mu_serial_getc(struct udevice *dev);
55
56static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
57{
58	struct bcm283x_mu_serial_plat *plat = dev_get_plat(dev);
59	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
60	struct bcm283x_mu_regs *regs = priv->regs;
61	u32 divider;
62
63	if (plat->skip_init)
64		goto out;
65
66	divider = plat->clock / (baudrate * 8);
67
68	writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
69	writel(divider - 1, &regs->baud);
70
71out:
72	/* Flush the RX queue - all data in there is bogus */
73	while (bcm283x_mu_serial_getc(dev) != -EAGAIN) ;
74
75	return 0;
76}
77
78static int bcm283x_mu_serial_getc(struct udevice *dev)
79{
80	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
81	struct bcm283x_mu_regs *regs = priv->regs;
82	u32 data;
83
84	/* Wait until there is data in the FIFO */
85	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
86		return -EAGAIN;
87
88	data = readl(&regs->io);
89
90	return (int)data;
91}
92
93static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
94{
95	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
96	struct bcm283x_mu_regs *regs = priv->regs;
97
98	/* Wait until there is space in the FIFO */
99	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
100		return -EAGAIN;
101
102	/* Send the character */
103	writel(data, &regs->io);
104
105	return 0;
106}
107
108static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
109{
110	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
111	struct bcm283x_mu_regs *regs = priv->regs;
112	unsigned int lsr;
113
114	lsr = readl(&regs->lsr);
115
116	if (input) {
117		schedule();
118		return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
119	} else {
120		return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
121	}
122}
123
124static const struct dm_serial_ops bcm283x_mu_serial_ops = {
125	.putc = bcm283x_mu_serial_putc,
126	.pending = bcm283x_mu_serial_pending,
127	.getc = bcm283x_mu_serial_getc,
128	.setbrg = bcm283x_mu_serial_setbrg,
129};
130
131#if CONFIG_IS_ENABLED(OF_CONTROL)
132static const struct udevice_id bcm283x_mu_serial_id[] = {
133	{.compatible = "brcm,bcm2835-aux-uart"},
134	{}
135};
136
137/*
138 * Check if this serial device is muxed
139 *
140 * The serial device will only work properly if it has been muxed to the serial
141 * pins by firmware. Check whether that happened here.
142 *
143 * Return: true if serial device is muxed, false if not
144 */
145static bool bcm283x_is_serial_muxed(void)
146{
147	int serial_gpio = 15;
148	struct udevice *dev;
149
150	if (uclass_first_device_err(UCLASS_PINCTRL, &dev))
151		return false;
152
153	if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT5)
154		return false;
155
156	return true;
157}
158
159static int bcm283x_mu_serial_probe(struct udevice *dev)
160{
161	struct bcm283x_mu_serial_plat *plat = dev_get_plat(dev);
162	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
163	fdt_addr_t addr;
164
165	/* Don't spawn the device if it's not muxed */
166	if (!bcm283x_is_serial_muxed())
167		return -ENODEV;
168
169	/*
170	 * Read the ofdata here rather than in an of_to_plat() method
171	 * since we need the soc simple-bus to be probed so that the 'ranges'
172	 * property is used.
173	 */
174	addr = dev_read_addr(dev);
175	if (addr == FDT_ADDR_T_NONE)
176		return -EINVAL;
177
178	plat->base = addr;
179	plat->clock = dev_read_u32_default(dev, "clock", 1);
180
181	/*
182	 * TODO: Reinitialization doesn't always work for now, just skip
183	 *       init always - we know we're already initialized
184	 */
185	plat->skip_init = true;
186
187	priv->regs = (struct bcm283x_mu_regs *)plat->base;
188
189	return 0;
190}
191#endif
192
193U_BOOT_DRIVER(serial_bcm283x_mu) = {
194	.name = "serial_bcm283x_mu",
195	.id = UCLASS_SERIAL,
196	.of_match = of_match_ptr(bcm283x_mu_serial_id),
197	.plat_auto	= sizeof(struct bcm283x_mu_serial_plat),
198	.probe = bcm283x_mu_serial_probe,
199	.ops = &bcm283x_mu_serial_ops,
200#if !CONFIG_IS_ENABLED(OF_CONTROL) || IS_ENABLED(CONFIG_OF_BOARD)
201	.flags = DM_FLAG_PRE_RELOC,
202#endif
203	.priv_auto	= sizeof(struct bcm283x_mu_priv),
204};
205