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/compiler.h>
27 
28 struct bcm283x_mu_regs {
29 	u32 io;
30 	u32 iir;
31 	u32 ier;
32 	u32 lcr;
33 	u32 mcr;
34 	u32 lsr;
35 	u32 msr;
36 	u32 scratch;
37 	u32 cntl;
38 	u32 stat;
39 	u32 baud;
40 };
41 
42 #define BCM283X_MU_LCR_DATA_SIZE_8	3
43 
44 #define BCM283X_MU_LSR_TX_IDLE		BIT(6)
45 /* This actually means not full, but is named not empty in the docs */
46 #define BCM283X_MU_LSR_TX_EMPTY		BIT(5)
47 #define BCM283X_MU_LSR_RX_READY		BIT(0)
48 
49 struct bcm283x_mu_priv {
50 	struct bcm283x_mu_regs *regs;
51 };
52 
53 static int bcm283x_mu_serial_getc(struct udevice *dev);
54 
55 static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
56 {
57 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
58 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
59 	struct bcm283x_mu_regs *regs = priv->regs;
60 	u32 divider;
61 
62 	if (plat->skip_init)
63 		goto out;
64 
65 	divider = plat->clock / (baudrate * 8);
66 
67 	writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
68 	writel(divider - 1, &regs->baud);
69 
70 out:
71 	/* Flush the RX queue - all data in there is bogus */
72 	while (bcm283x_mu_serial_getc(dev) != -EAGAIN) ;
73 
74 	return 0;
75 }
76 
77 static int bcm283x_mu_serial_probe(struct udevice *dev)
78 {
79 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
80 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
81 
82 	priv->regs = (struct bcm283x_mu_regs *)plat->base;
83 
84 	return 0;
85 }
86 
87 static int bcm283x_mu_serial_getc(struct udevice *dev)
88 {
89 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
90 	struct bcm283x_mu_regs *regs = priv->regs;
91 	u32 data;
92 
93 	/* Wait until there is data in the FIFO */
94 	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
95 		return -EAGAIN;
96 
97 	data = readl(&regs->io);
98 
99 	return (int)data;
100 }
101 
102 static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
103 {
104 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
105 	struct bcm283x_mu_regs *regs = priv->regs;
106 
107 	/* Wait until there is space in the FIFO */
108 	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
109 		return -EAGAIN;
110 
111 	/* Send the character */
112 	writel(data, &regs->io);
113 
114 	return 0;
115 }
116 
117 static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
118 {
119 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
120 	struct bcm283x_mu_regs *regs = priv->regs;
121 	unsigned int lsr;
122 
123 	lsr = readl(&regs->lsr);
124 
125 	if (input) {
126 		WATCHDOG_RESET();
127 		return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
128 	} else {
129 		return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
130 	}
131 }
132 
133 static const struct dm_serial_ops bcm283x_mu_serial_ops = {
134 	.putc = bcm283x_mu_serial_putc,
135 	.pending = bcm283x_mu_serial_pending,
136 	.getc = bcm283x_mu_serial_getc,
137 	.setbrg = bcm283x_mu_serial_setbrg,
138 };
139 
140 #if CONFIG_IS_ENABLED(OF_CONTROL)
141 static const struct udevice_id bcm283x_mu_serial_id[] = {
142 	{.compatible = "brcm,bcm2835-aux-uart"},
143 	{}
144 };
145 
146 /*
147  * Check if this serial device is muxed
148  *
149  * The serial device will only work properly if it has been muxed to the serial
150  * pins by firmware. Check whether that happened here.
151  *
152  * @return true if serial device is muxed, false if not
153  */
154 static bool bcm283x_is_serial_muxed(void)
155 {
156 	int serial_gpio = 15;
157 	struct udevice *dev;
158 
159 	if (uclass_first_device(UCLASS_PINCTRL, &dev) || !dev)
160 		return false;
161 
162 	if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT5)
163 		return false;
164 
165 	return true;
166 }
167 
168 static int bcm283x_mu_serial_ofdata_to_platdata(struct udevice *dev)
169 {
170 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
171 	fdt_addr_t addr;
172 
173 	/* Don't spawn the device if it's not muxed */
174 	if (!bcm283x_is_serial_muxed())
175 		return -ENODEV;
176 
177 	addr = devfdt_get_addr(dev);
178 	if (addr == FDT_ADDR_T_NONE)
179 		return -EINVAL;
180 
181 	plat->base = addr;
182 	plat->clock = dev_read_u32_default(dev, "clock", 1);
183 
184 	/*
185 	 * TODO: Reinitialization doesn't always work for now, just skip
186 	 *       init always - we know we're already initialized
187 	 */
188 	plat->skip_init = true;
189 
190 	return 0;
191 }
192 #endif
193 
194 U_BOOT_DRIVER(serial_bcm283x_mu) = {
195 	.name = "serial_bcm283x_mu",
196 	.id = UCLASS_SERIAL,
197 	.of_match = of_match_ptr(bcm283x_mu_serial_id),
198 	.ofdata_to_platdata = of_match_ptr(bcm283x_mu_serial_ofdata_to_platdata),
199 	.platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
200 	.probe = bcm283x_mu_serial_probe,
201 	.ops = &bcm283x_mu_serial_ops,
202 	.flags = DM_FLAG_PRE_RELOC,
203 	.priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
204 };
205