1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2016 Stefan Roese <sr@denx.de>
4 * Copyright (C) 2021 Pali Rohár <pali@kernel.org>
12 #include <asm/arch/cpu.h>
24 #define UART_RX_REG 0x00
25 #define UART_TX_REG 0x04
26 #define UART_CTRL_REG 0x08
27 #define UART_STATUS_REG 0x0c
28 #define UART_BAUD_REG 0x10
29 #define UART_POSSR_REG 0x14
31 #define UART_STATUS_RX_RDY 0x10
32 #define UART_STATUS_TX_EMPTY 0x40
33 #define UART_STATUS_TXFIFO_FULL 0x800
35 #define UART_CTRL_RXFIFO_RESET 0x4000
36 #define UART_CTRL_TXFIFO_RESET 0x8000
38 static int mvebu_serial_putc(struct udevice *dev, const char ch)
40 struct mvebu_plat *plat = dev_get_plat(dev);
41 void __iomem *base = plat->base;
43 if (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
46 writel(ch, base + UART_TX_REG);
51 static int mvebu_serial_getc(struct udevice *dev)
53 struct mvebu_plat *plat = dev_get_plat(dev);
54 void __iomem *base = plat->base;
56 if (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
59 return readl(base + UART_RX_REG) & 0xff;
62 static int mvebu_serial_pending(struct udevice *dev, bool input)
64 struct mvebu_plat *plat = dev_get_plat(dev);
65 void __iomem *base = plat->base;
68 if (readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY)
71 if (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
78 static int mvebu_serial_setbrg(struct udevice *dev, int baudrate)
80 struct mvebu_plat *plat = dev_get_plat(dev);
81 void __iomem *base = plat->base;
87 * baudrate = clock / 16 / divider
90 divider = DIV_ROUND_CLOSEST(plat->tbg_rate, baudrate * 16 * d1 * d2);
93 * Set Programmable Oversampling Stack to 0,
94 * UART defaults to 16x scheme
100 else if (divider > 1023) {
102 * If divider is too high for selected baudrate then set
103 * divider d1 to the maximal value 6.
106 divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
107 baudrate * 16 * d1 * d2);
110 else if (divider > 1023) {
112 * If divider is still too high then set also divider
113 * d2 to the maximal value 6.
116 divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
117 baudrate * 16 * d1 * d2);
120 else if (divider > 1023) {
122 * And if divider is still to high then
123 * use oversampling with maximal factor 63.
125 oversampling = (63 << 0) | (63 << 8) |
126 (63 << 16) | (63 << 24);
127 divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
128 baudrate * 63 * d1 * d2);
131 else if (divider > 1023)
137 divider |= BIT(19); /* Do not use XTAL as a base clock */
138 divider |= d1 << 15; /* Set d1 divider */
139 divider |= d2 << 12; /* Set d2 divider */
140 divider |= plat->tbg_idx << 10; /* Use selected TBG as a base clock */
142 while (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
144 writel(divider, base + UART_BAUD_REG);
145 writel(oversampling, base + UART_POSSR_REG);
150 static int mvebu_serial_probe(struct udevice *dev)
152 struct mvebu_plat *plat = dev_get_plat(dev);
153 void __iomem *base = plat->base;
154 struct udevice *nb_clk;
158 nb_clk_node = ofnode_by_compatible(ofnode_null(),
159 "marvell,armada-3700-periph-clock-nb");
160 if (!ofnode_valid(nb_clk_node)) {
161 printf("%s: NB periph clock node not available\n", __func__);
165 res = device_get_global_by_ofnode(nb_clk_node, &nb_clk);
167 printf("%s: Cannot get NB periph clock\n", __func__);
172 * Choose the TBG clock with lowest frequency which allows to configure
173 * UART also at lower baudrates.
175 for (i = 0; i < 4; i++) {
179 res = clk_get_by_index_nodev(nb_clk_node, i, &clk);
181 printf("%s: Cannot get TBG clock %i: %i\n", __func__,
186 rate = clk_get_rate(&clk);
187 if (!rate || IS_ERR_VALUE(rate)) {
188 printf("%s: Cannot get rate for TBG clock %i\n",
193 if (!i || plat->tbg_rate > rate) {
194 plat->tbg_rate = rate;
200 writel(UART_CTRL_RXFIFO_RESET | UART_CTRL_TXFIFO_RESET,
201 base + UART_CTRL_REG);
203 /* No Parity, 1 Stop */
204 writel(0, base + UART_CTRL_REG);
209 static int mvebu_serial_remove(struct udevice *dev)
211 struct mvebu_plat *plat = dev_get_plat(dev);
212 void __iomem *base = plat->base;
213 ulong new_parent_rate, parent_rate;
214 u32 new_divider, divider;
215 u32 new_oversampling;
221 * Switch UART base clock back to XTAL because older Linux kernel
222 * expects it. Otherwise it does not calculate UART divisor correctly
223 * and therefore UART does not work in kernel.
225 divider = readl(base + UART_BAUD_REG);
226 if (!(divider & BIT(19))) /* UART already uses XTAL */
229 /* Read current divisors settings */
230 d1 = (divider >> 15) & 7;
231 d2 = (divider >> 12) & 7;
232 parent_rate = plat->tbg_rate;
234 oversampling = readl(base + UART_POSSR_REG) & 63;
238 /* Calculate new divisor against XTAL clock without changing baudrate */
239 new_oversampling = 0;
240 new_parent_rate = get_ref_clk() * 1000000;
241 new_divider = DIV_ROUND_CLOSEST(new_parent_rate * divider * d1 * d2 *
242 oversampling, parent_rate * 16);
245 * UART does not work reliably when XTAL divisor is smaller than 4.
246 * In this case we do not switch UART parent to XTAL. User either
247 * configured unsupported settings or has newer kernel with patches
248 * which allow usage of non-XTAL clock as a parent clock.
254 * If new divisor is larger than maximal supported, try to switch
255 * from default x16 scheme to oversampling with maximal factor 63.
257 if (new_divider > 1023) {
258 new_oversampling = 63;
259 new_divider = DIV_ROUND_CLOSEST(new_parent_rate * divider * d1 *
261 parent_rate * new_oversampling);
262 if (new_divider < 4 || new_divider > 1023)
266 /* wait until TX empty */
267 while (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
270 /* external reset of UART via North Bridge Peripheral */
271 nb_rst = readl(MVEBU_REGISTER(0x12400));
272 writel(nb_rst & ~BIT(3), MVEBU_REGISTER(0x12400));
273 writel(nb_rst | BIT(3), MVEBU_REGISTER(0x12400));
275 /* set baudrate and oversampling */
276 writel(new_divider, base + UART_BAUD_REG);
277 writel(new_oversampling, base + UART_POSSR_REG);
279 /* No Parity, 1 Stop */
280 writel(0, base + UART_CTRL_REG);
285 static int mvebu_serial_of_to_plat(struct udevice *dev)
287 struct mvebu_plat *plat = dev_get_plat(dev);
289 plat->base = dev_read_addr_ptr(dev);
294 static const struct dm_serial_ops mvebu_serial_ops = {
295 .putc = mvebu_serial_putc,
296 .pending = mvebu_serial_pending,
297 .getc = mvebu_serial_getc,
298 .setbrg = mvebu_serial_setbrg,
301 static const struct udevice_id mvebu_serial_ids[] = {
302 { .compatible = "marvell,armada-3700-uart" },
306 U_BOOT_DRIVER(serial_mvebu) = {
307 .name = "serial_mvebu",
309 .of_match = mvebu_serial_ids,
310 .of_to_plat = mvebu_serial_of_to_plat,
311 .plat_auto = sizeof(struct mvebu_plat),
312 .probe = mvebu_serial_probe,
313 .remove = mvebu_serial_remove,
314 .flags = DM_FLAG_OS_PREPARE,
315 .ops = &mvebu_serial_ops,
318 #ifdef CONFIG_DEBUG_MVEBU_A3700_UART
320 #include <debug_uart.h>
322 static inline void _debug_uart_init(void)
324 void __iomem *base = (void __iomem *)CONFIG_VAL(DEBUG_UART_BASE);
325 u32 parent_rate, divider;
328 writel(UART_CTRL_RXFIFO_RESET | UART_CTRL_TXFIFO_RESET,
329 base + UART_CTRL_REG);
331 /* No Parity, 1 Stop */
332 writel(0, base + UART_CTRL_REG);
336 * baudrate = clock / 16 / divider
338 parent_rate = (readl(MVEBU_REGISTER(0x13808)) & BIT(9)) ?
340 divider = DIV_ROUND_CLOSEST(parent_rate, CONFIG_BAUDRATE * 16);
341 writel(divider, base + UART_BAUD_REG);
344 * Set Programmable Oversampling Stack to 0,
345 * UART defaults to 16x scheme
347 writel(0, base + UART_POSSR_REG);
350 static inline void _debug_uart_putc(int ch)
352 void __iomem *base = (void __iomem *)CONFIG_VAL(DEBUG_UART_BASE);
354 while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
357 writel(ch, base + UART_TX_REG);