[Skiboot] [PATCH 25/32] xive: Add helpers to encode and decode VP numbers

[Benjamin Herrenschmidt]

The VP numbers passed to the OS are encoded in a specific
way as to permit the use of HW PIR as valid VPs and as to
encode the order of the VP allocation as part of the VP
number. The encoding allows for the block group mode split
blocks of VPs to still appear contiguous to the OS.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
 hw/xive.c | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 145 insertions(+), 5 deletions(-)

diff --git a/hw/xive.c b/hw/xive.c
index a7a37a7..266e259 100644
--- a/hw/xive.c
+++ b/hw/xive.c
@@ -426,6 +426,148 @@ static uint32_t xive_block_count;
 #define VP2PIR(__blk, __idx)	(P9_PIRFROMLOCALCPU(((__idx) >> 7) & 0xf, (__idx) & 0x7f))
 #endif
 
+/* Decoding of OPAL API VP IDs. The VP IDs are encoded as follow
+ *
+ * Block group mode:
+ *
+ * -----------------------------------
+ * |GVEOOOOO|                   INDEX|
+ * -----------------------------------
+ *  ||   |
+ *  ||  Order
+ *  |Virtual
+ *  Group
+ *
+ * G (Group)   : Set to 1 for a group VP (not currently supported)
+ * V (Virtual) : Set to 1 for an allocated VP (vs. a physical processor ID)
+ * E (Error)   : Should never be 1, used internally for errors
+ * O (Order)   : Allocation order of the VP block
+ *
+ * The conversion is thus done as follow (groups aren't implemented yet)
+ *
+ *  If V=0, O must be 0 and 24-bit INDEX value is the PIR
+ *  If V=1, the order O group is allocated such that if N is the number of
+ *          chip bits considered for allocation (*)
+ *          then the INDEX is constructed as follow (bit numbers such as 0=LSB)
+ *           - bottom O-N bits is the index within the "VP block"
+ *           - next N bits is the XIVE blockID of the VP
+ *           - the remaining bits is the per-chip "base"
+ *          so the conversion consists of "extracting" the block ID and moving
+ *          down the upper bits by N bits.
+ *
+ * In non-block-group mode, the difference is that the blockID is
+ * on the left of the index (the entire VP block is in a single
+ * block ID)
+ */
+#ifdef USE_BLOCK_GROUP_MODE
+
+/* VP allocation */
+static uint32_t xive_chips_alloc_bits = 0;
+
+/* VP# decoding/encoding */
+static bool xive_decode_vp(uint32_t vp, uint32_t *blk, uint32_t *idx,
+			   uint8_t *order, bool *group)
+{
+	uint32_t o = (vp >> 24) & 0x1f;
+	uint32_t n = xive_chips_alloc_bits;
+	uint32_t index = vp & 0x00ffffff;
+	uint32_t imask = (1 << (o - n)) - 1;
+
+	/* Groups not supported yet */
+	if ((vp >> 31) & 1)
+		return false;
+	if (group)
+		*group = false;
+
+	/* PIR case */
+	if (((vp >> 30) & 1) == 0) {
+		if (blk)
+			*blk = PIR2VP_BLK(index);
+		if (idx)
+			*idx = PIR2VP_IDX(index);
+		return true;
+	}
+
+	/* Ensure o > n, we have *at least* 2 VPs per block */
+	if (o <= n)
+		return false;
+
+	/* Combine the index base and index */
+	if (idx)
+		*idx = ((index >> n) & ~imask) | (index & imask);
+	/* Extract block ID */
+	if (blk)
+		*blk = (index >> (o - n)) & ((1 << n) - 1);
+
+	/* Return order as well if asked for */
+	if (order)
+		*order = o;
+
+	return true;
+}
+
+static uint32_t xive_encode_vp(uint32_t blk, uint32_t idx, uint32_t order)
+{
+	uint32_t vp = 0x40000000 | (order << 24);
+	uint32_t n = xive_chips_alloc_bits;
+	uint32_t imask = (1 << (order - n)) - 1;
+
+	vp |= (idx & ~imask) << n;
+	vp |= blk << (order - n);
+	vp |= idx & imask;
+	return  vp;
+}
+
+#else /* USE_BLOCK_GROUP_MODE */
+
+/* VP# decoding/encoding */
+static bool xive_decode_vp(uint32_t vp, uint32_t *blk, uint32_t *idx,
+			   uint8_t *order, bool *group)
+{
+	uint32_t o = (vp >> 24) & 0x1f;
+	uint32_t index = vp & 0x00ffffff;
+	uint32_t imask = (1 << o) - 1;
+
+	/* Groups not supported yet */
+	if ((vp >> 31) & 1)
+		return false;
+	if (group)
+		*group = false;
+
+	/* PIR case */
+	if (((vp >> 30) & 1) == 0) {
+		if (blk)
+			*blk = PIR2VP_BLK(index);
+		if (idx)
+			*idx = PIR2VP_IDX(index);
+		return true;
+	}
+
+	/* Ensure o > 0, we have *at least* 2 VPs per block */
+	if (o == 0)
+		return false;
+
+	/* Extract index */
+	if (idx)
+		*idx = index & imask;
+	/* Extract block ID */
+	if (blk)
+		*blk = index >> o;
+
+	/* Return order as well if asked for */
+	if (order)
+		*order = o;
+
+	return true;
+}
+
+static uint32_t xive_encode_vp(uint32_t blk, uint32_t idx, uint32_t order)
+{
+	return 0x40000000 | (order << 24) | (blk << order) | idx;
+}
+
+#endif /* !USE_BLOCK_GROUP_MODE */
+
 #define xive_regw(__x, __r, __v) \
 	__xive_regw(__x, __r, X_##__r, __v, #__r)
 #define xive_regr(__x, __r) \
@@ -1686,11 +1828,9 @@ static inline bool xive_eq_for_target(uint32_t target, uint8_t prio,
 	if (prio > 7)
 		return false;
 
-	/* XXX This will have to change when having VPs that aren't
-	 * the physical processors
-	 */
-	vp_blk = PIR2VP_BLK(target);
-	vp_idx = PIR2VP_IDX(target);
+	/* Get the VP block/index from the target word */
+	if (!xive_decode_vp(target, &vp_blk, &vp_idx, NULL, NULL))
+		return false;
 
 	/* Grab the target VP's XIVE */
 	x = xive_from_pc_blk(vp_blk);
-- 
2.7.4