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>
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@ -71,11 +71,33 @@ static int opal_xscom_err_xlate(int64_t rc)
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}
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}
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static u64 opal_scom_unmangle(u64 reg)
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{
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/*
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* XSCOM indirect addresses have the top bit set. Additionally
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* the reset of the top 3 nibbles is always 0.
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*
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* Because the debugfs interface uses signed offsets and shifts
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* the address left by 3, we basically cannot use the top 4 bits
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* of the 64-bit address, and thus cannot use the indirect bit.
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*
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* To deal with that, we support the indirect bit being in bit
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* 4 (IBM notation) instead of bit 0 in this API, we do the
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* conversion here. To leave room for further xscom address
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* expansion, we only clear out the top byte
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*
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*/
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if (reg & (1ull << 59))
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reg = (reg & ~(0xffull << 56)) | (1ull << 63);
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return reg;
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}
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static int opal_scom_read(scom_map_t map, u64 reg, u64 *value)
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{
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struct opal_scom_map *m = map;
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int64_t rc;
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reg = opal_scom_unmangle(reg);
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rc = opal_xscom_read(m->chip, m->addr + reg, (uint64_t *)__pa(value));
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return opal_xscom_err_xlate(rc);
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}
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@ -85,6 +107,7 @@ static int opal_scom_write(scom_map_t map, u64 reg, u64 value)
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struct opal_scom_map *m = map;
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int64_t rc;
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reg = opal_scom_unmangle(reg);
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rc = opal_xscom_write(m->chip, m->addr + reg, value);
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return opal_xscom_err_xlate(rc);
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}
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