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
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
bcm283x_mu_serial_setbrg(struct udevice * dev,int baudrate)56 static 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, ®s->lcr);
69 writel(divider - 1, ®s->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
bcm283x_mu_serial_getc(struct udevice * dev)78 static 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(®s->lsr) & BCM283X_MU_LSR_RX_READY))
86 return -EAGAIN;
87
88 data = readl(®s->io);
89
90 return (int)data;
91 }
92
bcm283x_mu_serial_putc(struct udevice * dev,const char data)93 static 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(®s->lsr) & BCM283X_MU_LSR_TX_EMPTY))
100 return -EAGAIN;
101
102 /* Send the character */
103 writel(data, ®s->io);
104
105 return 0;
106 }
107
bcm283x_mu_serial_pending(struct udevice * dev,bool input)108 static 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(®s->lsr);
115
116 if (input) {
117 WATCHDOG_RESET();
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
124 static 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)
132 static 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 */
bcm283x_is_serial_muxed(void)145 static bool bcm283x_is_serial_muxed(void)
146 {
147 int serial_gpio = 15;
148 struct udevice *dev;
149
150 if (uclass_first_device(UCLASS_PINCTRL, &dev) || !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
bcm283x_mu_serial_probe(struct udevice * dev)159 static 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
193 U_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) || CONFIG_IS_ENABLED(OF_BOARD)
201 .flags = DM_FLAG_PRE_RELOC,
202 #endif
203 .priv_auto = sizeof(struct bcm283x_mu_priv),
204 };
205