1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * (c) 2015 Paul Thacker <paul.thacker@microchip.com>
4 *
5 */
6 #include <common.h>
7 #include <clk.h>
8 #include <dm.h>
9 #include <malloc.h>
10 #include <serial.h>
11 #include <wait_bit.h>
12 #include <asm/global_data.h>
13 #include <linux/bitops.h>
14 #include <mach/pic32.h>
15 #include <dt-bindings/clock/microchip,clock.h>
16
17 DECLARE_GLOBAL_DATA_PTR;
18
19 /* UART Control Registers */
20 #define U_MOD 0x00
21 #define U_MODCLR (U_MOD + _CLR_OFFSET)
22 #define U_MODSET (U_MOD + _SET_OFFSET)
23 #define U_STA 0x10
24 #define U_STACLR (U_STA + _CLR_OFFSET)
25 #define U_STASET (U_STA + _SET_OFFSET)
26 #define U_TXR 0x20
27 #define U_RXR 0x30
28 #define U_BRG 0x40
29
30 /* U_MOD bits */
31 #define UART_ENABLE BIT(15)
32
33 /* U_STA bits */
34 #define UART_RX_ENABLE BIT(12)
35 #define UART_TX_BRK BIT(11)
36 #define UART_TX_ENABLE BIT(10)
37 #define UART_TX_FULL BIT(9)
38 #define UART_TX_EMPTY BIT(8)
39 #define UART_RX_OVER BIT(1)
40 #define UART_RX_DATA_AVAIL BIT(0)
41
42 struct pic32_uart_priv {
43 void __iomem *base;
44 ulong uartclk;
45 };
46
47 /*
48 * Initialize the serial port with the given baudrate.
49 * The settings are always 8 data bits, no parity, 1 stop bit, no start bits.
50 */
pic32_serial_init(void __iomem * base,ulong clk,u32 baudrate)51 static int pic32_serial_init(void __iomem *base, ulong clk, u32 baudrate)
52 {
53 u32 div = DIV_ROUND_CLOSEST(clk, baudrate * 16);
54
55 /* wait for TX FIFO to empty */
56 wait_for_bit_le32(base + U_STA, UART_TX_EMPTY,
57 true, CONFIG_SYS_HZ, false);
58
59 /* send break */
60 writel(UART_TX_BRK, base + U_STASET);
61
62 /* disable and clear mode */
63 writel(0, base + U_MOD);
64 writel(0, base + U_STA);
65
66 /* set baud rate generator */
67 writel(div - 1, base + U_BRG);
68
69 /* enable the UART for TX and RX */
70 writel(UART_TX_ENABLE | UART_RX_ENABLE, base + U_STASET);
71
72 /* enable the UART */
73 writel(UART_ENABLE, base + U_MODSET);
74 return 0;
75 }
76
77 /* Check whether any char pending in RX fifo */
pic32_uart_pending_input(void __iomem * base)78 static int pic32_uart_pending_input(void __iomem *base)
79 {
80 /* check if rx buffer overrun error has occurred */
81 if (readl(base + U_STA) & UART_RX_OVER) {
82 readl(base + U_RXR);
83
84 /* clear overrun error to keep receiving */
85 writel(UART_RX_OVER, base + U_STACLR);
86 }
87
88 /* In PIC32 there is no way to know number of outstanding
89 * chars in rx-fifo. Only it can be known whether there is any.
90 */
91 return readl(base + U_STA) & UART_RX_DATA_AVAIL;
92 }
93
pic32_uart_pending(struct udevice * dev,bool input)94 static int pic32_uart_pending(struct udevice *dev, bool input)
95 {
96 struct pic32_uart_priv *priv = dev_get_priv(dev);
97
98 if (input)
99 return pic32_uart_pending_input(priv->base);
100
101 return !(readl(priv->base + U_STA) & UART_TX_EMPTY);
102 }
103
pic32_uart_setbrg(struct udevice * dev,int baudrate)104 static int pic32_uart_setbrg(struct udevice *dev, int baudrate)
105 {
106 struct pic32_uart_priv *priv = dev_get_priv(dev);
107
108 return pic32_serial_init(priv->base, priv->uartclk, baudrate);
109 }
110
pic32_uart_putc(struct udevice * dev,const char ch)111 static int pic32_uart_putc(struct udevice *dev, const char ch)
112 {
113 struct pic32_uart_priv *priv = dev_get_priv(dev);
114
115 /* Check if Tx FIFO is full */
116 if (readl(priv->base + U_STA) & UART_TX_FULL)
117 return -EAGAIN;
118
119 /* pump the char to tx buffer */
120 writel(ch, priv->base + U_TXR);
121
122 return 0;
123 }
124
pic32_uart_getc(struct udevice * dev)125 static int pic32_uart_getc(struct udevice *dev)
126 {
127 struct pic32_uart_priv *priv = dev_get_priv(dev);
128
129 /* return error if RX fifo is empty */
130 if (!pic32_uart_pending_input(priv->base))
131 return -EAGAIN;
132
133 /* read the character from rx buffer */
134 return readl(priv->base + U_RXR) & 0xff;
135 }
136
pic32_uart_probe(struct udevice * dev)137 static int pic32_uart_probe(struct udevice *dev)
138 {
139 struct pic32_uart_priv *priv = dev_get_priv(dev);
140 struct clk clk;
141 fdt_addr_t addr;
142 fdt_size_t size;
143 int ret;
144
145 /* get address */
146 addr = fdtdec_get_addr_size(gd->fdt_blob, dev_of_offset(dev), "reg",
147 &size);
148 if (addr == FDT_ADDR_T_NONE)
149 return -EINVAL;
150
151 priv->base = ioremap(addr, size);
152
153 /* get clock rate */
154 ret = clk_get_by_index(dev, 0, &clk);
155 if (ret < 0)
156 return ret;
157 priv->uartclk = clk_get_rate(&clk);
158 clk_free(&clk);
159
160 /* initialize serial */
161 return pic32_serial_init(priv->base, priv->uartclk, CONFIG_BAUDRATE);
162 }
163
164 static const struct dm_serial_ops pic32_uart_ops = {
165 .putc = pic32_uart_putc,
166 .pending = pic32_uart_pending,
167 .getc = pic32_uart_getc,
168 .setbrg = pic32_uart_setbrg,
169 };
170
171 static const struct udevice_id pic32_uart_ids[] = {
172 { .compatible = "microchip,pic32mzda-uart" },
173 {}
174 };
175
176 U_BOOT_DRIVER(pic32_serial) = {
177 .name = "pic32-uart",
178 .id = UCLASS_SERIAL,
179 .of_match = pic32_uart_ids,
180 .probe = pic32_uart_probe,
181 .ops = &pic32_uart_ops,
182 .priv_auto = sizeof(struct pic32_uart_priv),
183 };
184
185 #ifdef CONFIG_DEBUG_UART_PIC32
186 #include <debug_uart.h>
187
_debug_uart_init(void)188 static inline void _debug_uart_init(void)
189 {
190 void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
191
192 pic32_serial_init(base, CONFIG_DEBUG_UART_CLOCK, CONFIG_BAUDRATE);
193 }
194
_debug_uart_putc(int ch)195 static inline void _debug_uart_putc(int ch)
196 {
197 writel(ch, CONFIG_DEBUG_UART_BASE + U_TXR);
198 }
199
200 DEBUG_UART_FUNCS
201 #endif
202