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powerpc/powernv: Add support for indirect XSCOM via debugfs 

Indirect XSCOM addresses normally have the top bit set (of the 64-bit
address). This doesn't work via the normal debugfs interface, so we use
a different encoding, which we need to convert before calling OPAL.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2013-10-10 19:19:15 +11:00
parent cda13552d5
commit 80546ac513
1 changed files with 23 additions and 0 deletions
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23
arch/powerpc/platforms/powernv/opal-xscom.c
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@ -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 debugfs 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);
}