[rtl] FPGA bkdr fix#30680
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The first commit of this PR was already merged as part of #30543 |
thommythomaso
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vogelpi
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a-will
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tgt_idx_err was not set when the index exceeded NumBkdrTgts because it was casted to a logic with fewer bits. The enum is now changed to an 8b enum such that the cast is not dropping any bits. Signed-off-by: Michael Gautschi <mgautschi@lowrisc.org>
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The e2e_bootstrap_disabled_fpga_cw340_rom_with_fake_keys FPGA test failed, but I've seen this failing for other PRs as well. The failure is not related to this change. |
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The enum was previously defined as
typedef enum logic [$clog2(NumBkdrTgts)-1:0]andNumBkdrTgtswas 12. Hence, the enum was 4bit wide.The index check (https://github.com/lowRISC/opentitan/blob/master/hw/ip/bkdr_loader/rtl/bkdr_loader.sv#L284)
assign tgt_idx_err = !(bkdr_idx_e'(reg2hw.control.target_idx.q) inside {BkdrValidTgts});It first casts the 8b target_idx signal to the enum size (dropping 4 bits). And then checks if the value is inside the valid targets. Hence, a
target_idxof 13 was seen as a legal value. Actually vivado was interpreting it as always false and was thus always reporting an invalid target.