Prevent TLWidthWidget from generating X outputs #2815
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Widening WidthWidgets contain an uninitialized data register. The first transaction through the widget may propagate that register's contents on the bus, which is logically correct but can propagates a X, violating our constraint that we never provide X in the payload of a valid xact. Fix by propagating in.bits.data, rather than the register, until the register has been written at least once. This is cheaper than resetting the register.
aswaterman
approved these changes
Apr 18, 2021
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Widening WidthWidgets contain an uninitialized data register. The first transaction through the widget may propagate that register's contents on the bus, which is logically correct but can propagates a X, violating our constraint that we never provide X in the payload of a valid xact.
Fix by propagating in.bits.data, rather than the register, until the register has been written at least once. This is cheaper than resetting the register.