1 /*
2  * (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
3  *
4  * Derived from pl01x code:
5  *
6  * (C) Copyright 2000
7  * Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
8  *
9  * (C) Copyright 2004
10  * ARM Ltd.
11  * Philippe Robin, <philippe.robin@arm.com>
12  *
13  * SPDX-License-Identifier:	GPL-2.0+
14  */
15 
16 /* Simple U-Boot driver for the BCM283x mini UART */
17 
18 #include <common.h>
19 #include <dm.h>
20 #include <errno.h>
21 #include <watchdog.h>
22 #include <asm/gpio.h>
23 #include <asm/io.h>
24 #include <serial.h>
25 #include <dm/platform_data/serial_bcm283x_mu.h>
26 #include <dm/pinctrl.h>
27 #include <linux/compiler.h>
28 
29 struct 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 
50 struct bcm283x_mu_priv {
51 	struct bcm283x_mu_regs *regs;
52 };
53 
54 static int bcm283x_mu_serial_getc(struct udevice *dev);
55 
56 static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
57 {
58 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(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 
71 out:
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 
78 static int bcm283x_mu_serial_probe(struct udevice *dev)
79 {
80 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
81 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
82 
83 	priv->regs = (struct bcm283x_mu_regs *)plat->base;
84 
85 	return 0;
86 }
87 
88 static int bcm283x_mu_serial_getc(struct udevice *dev)
89 {
90 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
91 	struct bcm283x_mu_regs *regs = priv->regs;
92 	u32 data;
93 
94 	/* Wait until there is data in the FIFO */
95 	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
96 		return -EAGAIN;
97 
98 	data = readl(&regs->io);
99 
100 	return (int)data;
101 }
102 
103 static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
104 {
105 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
106 	struct bcm283x_mu_regs *regs = priv->regs;
107 
108 	/* Wait until there is space in the FIFO */
109 	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
110 		return -EAGAIN;
111 
112 	/* Send the character */
113 	writel(data, &regs->io);
114 
115 	return 0;
116 }
117 
118 static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
119 {
120 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
121 	struct bcm283x_mu_regs *regs = priv->regs;
122 	unsigned int lsr;
123 
124 	lsr = readl(&regs->lsr);
125 
126 	if (input) {
127 		WATCHDOG_RESET();
128 		return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
129 	} else {
130 		return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
131 	}
132 }
133 
134 static const struct dm_serial_ops bcm283x_mu_serial_ops = {
135 	.putc = bcm283x_mu_serial_putc,
136 	.pending = bcm283x_mu_serial_pending,
137 	.getc = bcm283x_mu_serial_getc,
138 	.setbrg = bcm283x_mu_serial_setbrg,
139 };
140 
141 #if CONFIG_IS_ENABLED(OF_CONTROL)
142 static const struct udevice_id bcm283x_mu_serial_id[] = {
143 	{.compatible = "brcm,bcm2835-aux-uart"},
144 	{}
145 };
146 
147 /*
148  * Check if this serial device is muxed
149  *
150  * The serial device will only work properly if it has been muxed to the serial
151  * pins by firmware. Check whether that happened here.
152  *
153  * @return true if serial device is muxed, false if not
154  */
155 static bool bcm283x_is_serial_muxed(void)
156 {
157 	int serial_gpio = 15;
158 	struct udevice *dev;
159 
160 	if (uclass_first_device(UCLASS_PINCTRL, &dev) || !dev)
161 		return false;
162 
163 	if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT5)
164 		return false;
165 
166 	return true;
167 }
168 
169 static int bcm283x_mu_serial_ofdata_to_platdata(struct udevice *dev)
170 {
171 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
172 	fdt_addr_t addr;
173 
174 	/* Don't spawn the device if it's not muxed */
175 	if (!bcm283x_is_serial_muxed())
176 		return -ENODEV;
177 
178 	addr = devfdt_get_addr(dev);
179 	if (addr == FDT_ADDR_T_NONE)
180 		return -EINVAL;
181 
182 	plat->base = addr;
183 	plat->clock = dev_read_u32_default(dev, "clock", 1);
184 
185 	/*
186 	 * TODO: Reinitialization doesn't always work for now, just skip
187 	 *       init always - we know we're already initialized
188 	 */
189 	plat->skip_init = true;
190 
191 	return 0;
192 }
193 #endif
194 
195 U_BOOT_DRIVER(serial_bcm283x_mu) = {
196 	.name = "serial_bcm283x_mu",
197 	.id = UCLASS_SERIAL,
198 	.of_match = of_match_ptr(bcm283x_mu_serial_id),
199 	.ofdata_to_platdata = of_match_ptr(bcm283x_mu_serial_ofdata_to_platdata),
200 	.platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
201 	.probe = bcm283x_mu_serial_probe,
202 	.ops = &bcm283x_mu_serial_ops,
203 	.flags = DM_FLAG_PRE_RELOC,
204 	.priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
205 };
206