Indirect XSCOM addresses normally have the top bit set (of the 64-bit
address). This doesn't work via the normal sysfs interface, so we use
a different encoding, which we need to convert before calling OPAL.
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
---
arch/powerpc/platforms/powernv/opal-xscom.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/arch/powerpc/platforms/powernv/opal-xscom.c
b/arch/powerpc/platforms/powernv/opal-xscom.c
index 09a90d8..23e52f3 100644
--- a/arch/powerpc/platforms/powernv/opal-xscom.c
+++ b/arch/powerpc/platforms/powernv/opal-xscom.c
@@ -71,11 +71,33 @@ static int opal_xscom_err_xlate(int64_t rc)
}
}
+static u64 opal_scom_unmangle(u64 reg)
+{
+ /*
+ * XSCOM indirect addresses have the top bit set. Additionally
+ * the reset of the top 3 nibbles is always 0.
+ *
+ * Because the sysfs interface uses signed offsets and shifts
+ * the address left by 3, we basically cannot use the top 4 bits
+ * of the 64-bit address, and thus cannot use the indirect bit.
+ *
+ * To deal with that, we support the indirect bit being in bit
+ * 4 (IBM notation) instead of bit 0 in this API, we do the
+ * conversion here. To leave room for further xscom address
+ * expansion, we only clear out the top byte
+ *
+ */
+ if (reg & (1ull << 59))
+ reg = (reg & ~(0xffull << 56)) | (1ull << 63);
+ return reg;
+}
+
static int opal_scom_read(scom_map_t map, u64 reg, u64 *value)
{
struct opal_scom_map *m = map;
int64_t rc;
+ reg = opal_scom_unmangle(reg);
rc = opal_xscom_read(m->chip, m->addr + reg, (uint64_t *)__pa(value));
return opal_xscom_err_xlate(rc);
}
@@ -85,6 +107,7 @@ static int opal_scom_write(scom_map_t map, u64 reg, u64
value)
struct opal_scom_map *m = map;
int64_t rc;
+ reg = opal_scom_unmangle(reg);
rc = opal_xscom_write(m->chip, m->addr + reg, value);
return opal_xscom_err_xlate(rc);
}
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