LXR linux/arch/powerpc/platforms/powernv/opal-xscom.c

   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 */
  28struct opal_scom_map {
  29        uint32_t chip;
  30        uint64_t addr;
  31};
  32
  33static 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 %pOF is not a SCOM controller\n",
  40                        __func__, dev);
  41                return SCOM_MAP_INVALID;
  42        }
  43        gcid = of_get_property(dev, "ibm,chip-id", NULL);
  44        if (!gcid) {
  45                pr_err("%s: device %pOF has no ibm,chip-id\n",
  46                        __func__, dev);
  47                return SCOM_MAP_INVALID;
  48        }
  49        m = kmalloc(sizeof(*m), 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
  58static void opal_scom_unmap(scom_map_t map)
  59{
  60        kfree(map);
  61}
  62
  63static 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
  74static u64 opal_scom_unmangle(u64 addr)
  75{
  76        u64 tmp;
  77
  78        /*
  79         * XSCOM addresses use the top nibble to set indirect mode and
  80         * its form.  Bits 4-11 are always 0.
  81         *
  82         * Because the debugfs interface uses signed offsets and shifts
  83         * the address left by 3, we basically cannot use the top 4 bits
  84         * of the 64-bit address, and thus cannot use the indirect bit.
  85         *
  86         * To deal with that, we support the indirect bits being in
  87         * bits 4-7 (IBM notation) instead of bit 0-3 in this API, we
  88         * do the conversion here.
  89         *
  90         * For in-kernel use, we don't need to do this mangling.  In
  91         * kernel won't have bits 4-7 set.
  92         *
  93         * So:
  94         *   debugfs will always   set 0-3 = 0 and clear 4-7
  95         *    kernel will always clear 0-3 = 0 and   set 4-7
  96         */
  97        tmp = addr;
  98        tmp  &= 0x0f00000000000000;
  99        addr &= 0xf0ffffffffffffff;
 100        addr |= tmp << 4;
 101
 102        return addr;
 103}
 104
 105static int opal_scom_read(scom_map_t map, u64 reg, u64 *value)
 106{
 107        struct opal_scom_map *m = map;
 108        int64_t rc;
 109        __be64 v;
 110
 111        reg = opal_scom_unmangle(m->addr + reg);
 112        rc = opal_xscom_read(m->chip, reg, (__be64 *)__pa(&v));
 113        *value = be64_to_cpu(v);
 114        return opal_xscom_err_xlate(rc);
 115}
 116
 117static int opal_scom_write(scom_map_t map, u64 reg, u64 value)
 118{
 119        struct opal_scom_map *m = map;
 120        int64_t rc;
 121
 122        reg = opal_scom_unmangle(m->addr + reg);
 123        rc = opal_xscom_write(m->chip, reg, value);
 124        return opal_xscom_err_xlate(rc);
 125}
 126
 127static const struct scom_controller opal_scom_controller = {
 128        .map    = opal_scom_map,
 129        .unmap  = opal_scom_unmap,
 130        .read   = opal_scom_read,
 131        .write  = opal_scom_write
 132};
 133
 134static int opal_xscom_init(void)
 135{
 136        if (firmware_has_feature(FW_FEATURE_OPAL))
 137                scom_init(&opal_scom_controller);
 138        return 0;
 139}
 140machine_arch_initcall(powernv, opal_xscom_init);
 141