udbg_scc.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * udbg for zilog scc ports as found on Apple PowerMacs
  4 *
  5 * Copyright (C) 2001-2005 PPC 64 Team, IBM Corp
  6 */
  7#include <linux/types.h>
  8#include <linux/of.h>
  9#include <asm/udbg.h>
 10#include <asm/processor.h>
 11#include <asm/io.h>
 12#include <asm/pmac_feature.h>
 13
 14extern u8 real_readb(volatile u8 __iomem  *addr);
 15extern void real_writeb(u8 data, volatile u8 __iomem *addr);
 16
 17#define	SCC_TXRDY	4
 18#define SCC_RXRDY	1
 19
 20static volatile u8 __iomem *sccc;
 21static volatile u8 __iomem *sccd;
 22
 23static void udbg_scc_putc(char c)
 24{
 25	if (sccc) {
 26		while ((in_8(sccc) & SCC_TXRDY) == 0)
 27			;
 28		out_8(sccd,  c);
 29		if (c == '\n')
 30			udbg_scc_putc('\r');
 31	}
 32}
 33
 34static int udbg_scc_getc_poll(void)
 35{
 36	if (sccc) {
 37		if ((in_8(sccc) & SCC_RXRDY) != 0)
 38			return in_8(sccd);
 39		else
 40			return -1;
 41	}
 42	return -1;
 43}
 44
 45static int udbg_scc_getc(void)
 46{
 47	if (sccc) {
 48		while ((in_8(sccc) & SCC_RXRDY) == 0)
 49			;
 50		return in_8(sccd);
 51	}
 52	return -1;
 53}
 54
 55static unsigned char scc_inittab[] = {
 56    13, 0,		/* set baud rate divisor */
 57    12, 0,
 58    14, 1,		/* baud rate gen enable, src=rtxc */
 59    11, 0x50,		/* clocks = br gen */
 60    5,  0xea,		/* tx 8 bits, assert DTR & RTS */
 61    4,  0x46,		/* x16 clock, 1 stop */
 62    3,  0xc1,		/* rx enable, 8 bits */
 63};
 64
 65void __init udbg_scc_init(int force_scc)
 66{
 67	const u32 *reg;
 68	unsigned long addr;
 69	struct device_node *stdout = NULL, *escc = NULL, *macio = NULL;
 70	struct device_node *ch, *ch_def = NULL, *ch_a = NULL;
 71	const char *path;
 72	int i;
 73
 74	escc = of_find_node_by_name(NULL, "escc");
 75	if (escc == NULL)
 76		goto bail;
 77	macio = of_get_parent(escc);
 78	if (macio == NULL)
 79		goto bail;
 80	path = of_get_property(of_chosen, "linux,stdout-path", NULL);
 81	if (path != NULL)
 82		stdout = of_find_node_by_path(path);
 83	for_each_child_of_node(escc, ch) {
 84		if (ch == stdout) {
 85			of_node_put(ch_def);
 86			ch_def = of_node_get(ch);
 87		}
 88		if (of_node_name_eq(ch, "ch-a")) {
 89			of_node_put(ch_a);
 90			ch_a = of_node_get(ch);
 91		}
 92	}
 93	if (ch_def == NULL && !force_scc)
 94		goto bail;
 95
 96	ch = ch_def ? ch_def : ch_a;
 97
 98	/* Get address within mac-io ASIC */
 99	reg = of_get_property(escc, "reg", NULL);
100	if (reg == NULL)
101		goto bail;
102	addr = reg[0];
103
104	/* Get address of mac-io PCI itself */
105	reg = of_get_property(macio, "assigned-addresses", NULL);
106	if (reg == NULL)
107		goto bail;
108	addr += reg[2];
109
110	/* Lock the serial port */
111	pmac_call_feature(PMAC_FTR_SCC_ENABLE, ch,
112			  PMAC_SCC_ASYNC | PMAC_SCC_FLAG_XMON, 1);
113
114	if (ch == ch_a)
115		addr += 0x20;
116	sccc = ioremap(addr & PAGE_MASK, PAGE_SIZE) ;
117	sccc += addr & ~PAGE_MASK;
118	sccd = sccc + 0x10;
119
120	mb();
121
122	for (i = 20000; i != 0; --i)
123		in_8(sccc);
124	out_8(sccc, 0x09);		/* reset A or B side */
125	out_8(sccc, 0xc0);
126
127	/* If SCC was the OF output port, read the BRG value, else
128	 * Setup for 38400 or 57600 8N1 depending on the machine
129	 */
130	if (ch_def != NULL) {
131		out_8(sccc, 13);
132		scc_inittab[1] = in_8(sccc);
133		out_8(sccc, 12);
134		scc_inittab[3] = in_8(sccc);
135	} else if (of_machine_is_compatible("RackMac1,1")
136		   || of_machine_is_compatible("RackMac1,2")
137		   || of_machine_is_compatible("MacRISC4")) {
138		/* Xserves and G5s default to 57600 */
139		scc_inittab[1] = 0;
140		scc_inittab[3] = 0;
141	} else {
142		/* Others default to 38400 */
143		scc_inittab[1] = 0;
144		scc_inittab[3] = 1;
145	}
146
147	for (i = 0; i < sizeof(scc_inittab); ++i)
148		out_8(sccc, scc_inittab[i]);
149
150
151	udbg_putc = udbg_scc_putc;
152	udbg_getc = udbg_scc_getc;
153	udbg_getc_poll = udbg_scc_getc_poll;
154
155	udbg_puts("Hello World !\n");
156
157 bail:
158	of_node_put(macio);
159	of_node_put(escc);
160	of_node_put(stdout);
161	of_node_put(ch_def);
162	of_node_put(ch_a);
163}
164
165#ifdef CONFIG_PPC64
166static void udbg_real_scc_putc(char c)
167{
168	while ((real_readb(sccc) & SCC_TXRDY) == 0)
169		;
170	real_writeb(c, sccd);
171	if (c == '\n')
172		udbg_real_scc_putc('\r');
173}
174
175void __init udbg_init_pmac_realmode(void)
176{
177	sccc = (volatile u8 __iomem *)0x80013020ul;
178	sccd = (volatile u8 __iomem *)0x80013030ul;
179
180	udbg_putc = udbg_real_scc_putc;
181	udbg_getc = NULL;
182	udbg_getc_poll = NULL;
183}
184#endif /* CONFIG_PPC64 */