005-tilegrid: XRAY_GTX_SITES to fuzz only the BONDED GTX quads

005-tilegrid skips GTX entirely on virtex7, and the reason is the
package rather than the fuzzer: xc7vx485t-ffg1761 bonds only about half
its GTX quads, an UNBONDED quad cannot be placed, and one unplaceable
site fails the whole run.  So the GT tiles a real design actually uses
went unmeasured, and their tilegrid entries stayed empty -- which is the
"key not found" / empty bits{} hole that fasm2frames then reports far
downstream.

XRAY_GTX_SITES takes a comma-separated site list and restricts the fuzz
to it, so a bonded quad can be measured and the unbonded ones are left
legitimately unmeasured instead of taking the run down with them.  On
this board the SGMII sits on GTXE2_CHANNEL_X1Y* / GTXE2_COMMON_X1Y0.

Unset, behaviour is exactly as before.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

fuzzers/005-tilegrid/gtx_channel/top.py

@@ -24,6 +24,18 @@ def gen_sites():
 
         for site_name, site_type in gridinfo.sites.items():
             if site_type in ['GTXE2_CHANNEL']:
+                # XRAY_GTX_SITES restricts the fuzz to a comma-separated list of
+                # site names.  Needed on virtex7: the xc7vx485t-ffg1761 package
+                # bonds only about half its GTX quads, and an UNBONDED quad
+                # cannot be placed, so fuzzing every site fails the whole run --
+                # which is why 005-tilegrid skips GTX for virtex7 entirely.
+                # Restricting to a bonded quad measures the tiles that a real
+                # design actually uses (this board's SGMII sits on
+                # GTXE2_CHANNEL_X1Y* / GTXE2_COMMON_X1Y0) and leaves the
+                # unbonded ones legitimately unmeasured.
+                want = os.getenv("XRAY_GTX_SITES")
+                if want and site_name not in want.split(','):
+                    continue
                 yield tile_name, site_name
 
 

fuzzers/005-tilegrid/gtx_common/top.py

@@ -24,6 +24,18 @@ def gen_sites():
 
         for site_name, site_type in gridinfo.sites.items():
             if site_type in ['GTXE2_COMMON']:
+                # XRAY_GTX_SITES restricts the fuzz to a comma-separated list of
+                # site names.  Needed on virtex7: the xc7vx485t-ffg1761 package
+                # bonds only about half its GTX quads, and an UNBONDED quad
+                # cannot be placed, so fuzzing every site fails the whole run --
+                # which is why 005-tilegrid skips GTX for virtex7 entirely.
+                # Restricting to a bonded quad measures the tiles that a real
+                # design actually uses (this board's SGMII sits on
+                # GTXE2_CHANNEL_X1Y* / GTXE2_COMMON_X1Y0) and leaves the
+                # unbonded ones legitimately unmeasured.
+                want = os.getenv("XRAY_GTX_SITES")
+                if want and site_name not in want.split(','):
+                    continue
                 yield tile_name, site_name