1 /*
2  * PowerNV LPC bus handling.
3  *
4  * Copyright 2013 IBM Corp.
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/of.h>
14 #include <linux/bug.h>
15 #include <linux/gfp.h>
16 #include <linux/slab.h>
17 
18 #include <asm/machdep.h>
19 #include <asm/firmware.h>
20 #include <asm/opal.h>
21 #include <asm/scom.h>
22 
23 /*
24  * We could probably fit that inside the scom_map_t
25  * which is a void* after all but it's really too ugly
26  * so let's kmalloc it for now
27  */
28 struct opal_scom_map {
29 	uint32_t chip;
30 	uint64_t addr;
31 };
32 
33 static scom_map_t opal_scom_map(struct device_node *dev, u64 reg, u64 count)
34 {
35 	struct opal_scom_map *m;
36 	const __be32 *gcid;
37 
38 	if (!of_get_property(dev, "scom-controller", NULL)) {
39 		pr_err("%s: device %s is not a SCOM controller\n",
40 			__func__, dev->full_name);
41 		return SCOM_MAP_INVALID;
42 	}
43 	gcid = of_get_property(dev, "ibm,chip-id", NULL);
44 	if (!gcid) {
45 		pr_err("%s: device %s has no ibm,chip-id\n",
46 			__func__, dev->full_name);
47 		return SCOM_MAP_INVALID;
48 	}
49 	m = kmalloc(sizeof(struct opal_scom_map), GFP_KERNEL);
50 	if (!m)
51 		return NULL;
52 	m->chip = be32_to_cpup(gcid);
53 	m->addr = reg;
54 
55 	return (scom_map_t)m;
56 }
57 
58 static void opal_scom_unmap(scom_map_t map)
59 {
60 	kfree(map);
61 }
62 
63 static int opal_xscom_err_xlate(int64_t rc)
64 {
65 	switch(rc) {
66 	case 0:
67 		return 0;
68 	/* Add more translations if necessary */
69 	default:
70 		return -EIO;
71 	}
72 }
73 
74 static u64 opal_scom_unmangle(u64 addr)
75 {
76 	/*
77 	 * XSCOM indirect addresses have the top bit set. Additionally
78 	 * the rest of the top 3 nibbles is always 0.
79 	 *
80 	 * Because the debugfs interface uses signed offsets and shifts
81 	 * the address left by 3, we basically cannot use the top 4 bits
82 	 * of the 64-bit address, and thus cannot use the indirect bit.
83 	 *
84 	 * To deal with that, we support the indirect bit being in bit
85 	 * 4 (IBM notation) instead of bit 0 in this API, we do the
86 	 * conversion here. To leave room for further xscom address
87 	 * expansion, we only clear out the top byte
88 	 *
89 	 * For in-kernel use, we also support the real indirect bit, so
90 	 * we test for any of the top 5 bits
91 	 *
92 	 */
93 	if (addr & (0x1full << 59))
94 		addr = (addr & ~(0xffull << 56)) | (1ull << 63);
95 	return addr;
96 }
97 
98 static int opal_scom_read(scom_map_t map, u64 reg, u64 *value)
99 {
100 	struct opal_scom_map *m = map;
101 	int64_t rc;
102 	__be64 v;
103 
104 	reg = opal_scom_unmangle(m->addr + reg);
105 	rc = opal_xscom_read(m->chip, reg, (__be64 *)__pa(&v));
106 	*value = be64_to_cpu(v);
107 	return opal_xscom_err_xlate(rc);
108 }
109 
110 static int opal_scom_write(scom_map_t map, u64 reg, u64 value)
111 {
112 	struct opal_scom_map *m = map;
113 	int64_t rc;
114 
115 	reg = opal_scom_unmangle(m->addr + reg);
116 	rc = opal_xscom_write(m->chip, reg, value);
117 	return opal_xscom_err_xlate(rc);
118 }
119 
120 static const struct scom_controller opal_scom_controller = {
121 	.map	= opal_scom_map,
122 	.unmap	= opal_scom_unmap,
123 	.read	= opal_scom_read,
124 	.write	= opal_scom_write
125 };
126 
127 static int opal_xscom_init(void)
128 {
129 	if (firmware_has_feature(FW_FEATURE_OPALv3))
130 		scom_init(&opal_scom_controller);
131 	return 0;
132 }
133 arch_initcall(opal_xscom_init);
134