From f183f8add218b43a82ec7603cb0d7952664a0b26 Mon Sep 17 00:00:00 2001
From: David Montero <davidmonterocrespo24@gmail.com>
Date: Fri, 12 Jun 2026 20:18:50 +0200
Subject: [PATCH] =?UTF-8?q?wip(picow):=20Phase=203=20instrumentation=20?=
 =?UTF-8?q?=E2=80=94=20confirm=20credit=20frame=20is=20queued+visible?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

debugInboundCount + STATUS-read tracking show initInbound=1, statusReads=2,
statusReadsWithPkt=2, finalInbound=1: the credit frame IS visible at both STATUS
reads (not a credit tight-loop). The driver reaches clm_load's F2-ready check
(passes) but the F2 IOCTL write never appears on the bus and bus_init returns.
Next: instrument the F2-write path. See findings.md F-13.
---
 .../picow-cyw43-boot-harness.investigate.test.ts      | 11 ++++++++++-
 frontend/src/simulation/cyw43/Cyw43Emulator.ts        |  3 +++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/frontend/src/__tests__/picow-cyw43-boot-harness.investigate.test.ts b/frontend/src/__tests__/picow-cyw43-boot-harness.investigate.test.ts
index 945f1e3f..a412d387 100644
--- a/frontend/src/__tests__/picow-cyw43-boot-harness.investigate.test.ts
+++ b/frontend/src/__tests__/picow-cyw43-boot-harness.investigate.test.ts
@@ -86,6 +86,9 @@ describe.skipIf(!process.env.CYW43_HARNESS)('Pico W cyw43 boot harness (investig
 
       // ── attach production Cyw43Emulator the way RP2040Simulator does ──
       const chip = new Cyw43Emulator();
+      const initInbound = chip.debugInboundCount();
+      let statusReadsWithPkt = 0;
+      let statusReads = 0;
       const sniffer = new PioBusSniffer();
       sniffer.setModeProvider(() => chip.isBigEndian());
       let pushCount = 0;
@@ -124,6 +127,11 @@ describe.skipIf(!process.env.CYW43_HARNESS)('Pico W cyw43 boot harness (investig
           } else if (ev.kind === 'payload') {
             // Histogram of decoded functions + capture EVERY F2 transfer.
             funcHist[ev.cmd.function & 3]++;
+            // Track SPI_STATUS reads and whether a frame was queued at the time.
+            if (!ev.cmd.write && ev.cmd.function === 0 && ev.cmd.address === 0x08) {
+              statusReads++;
+              if (chip.debugInboundCount() > 0) statusReadsWithPkt++;
+            }
             if (ev.cmd.function === 2 && f2Log.length < 60) {
               f2Log.push(`${ev.cmd.write ? 'WR' : 'RD'} F2 a=0x${ev.cmd.address.toString(16)} len=${ev.payload.length || ev.readBytes}`);
             }
@@ -238,7 +246,8 @@ describe.skipIf(!process.env.CYW43_HARNESS)('Pico W cyw43 boot harness (investig
           '===== SERIAL OUTPUT (tail 2500) =====\n' + serial.slice(-2500) + '\n\n' +
           '===== TOP COMMAND COUNTS (poll loops) =====\n' +
           polls.map(([k, n]) => `  ${String(n).padStart(6)}  ${k}`).join('\n') + '\n\n' +
-          `===== FUNCTION HISTOGRAM F0..F3 = ${funcHist.join(',')} =====\n\n` +
+          `===== FUNCTION HISTOGRAM F0..F3 = ${funcHist.join(',')} =====\n` +
+          `===== initInbound=${initInbound} statusReads=${statusReads} statusReadsWithPkt=${statusReadsWithPkt} finalInbound=${chip.debugInboundCount()} =====\n\n` +
           '===== F2/IOCTL TRANSFERS (total seen, non-ring) =====\n' +
           `count=${f2Log.length}\n` + f2Log.join('\n') + '\n\n' +
           '===== TRACE TAIL (post-firmware) =====\n' + trace.slice(-120).join('\n') + '\n';
diff --git a/frontend/src/simulation/cyw43/Cyw43Emulator.ts b/frontend/src/simulation/cyw43/Cyw43Emulator.ts
index 43d5f6ed..be3f85e0 100644
--- a/frontend/src/simulation/cyw43/Cyw43Emulator.ts
+++ b/frontend/src/simulation/cyw43/Cyw43Emulator.ts
@@ -243,6 +243,9 @@ export class Cyw43Emulator {
   /** True once the driver has switched the bus to 32-bit big-endian. */
   isBigEndian(): boolean { return this.bigEndian; }
 
+  /** Debug: queued chip→host frame count (for harness instrumentation). */
+  debugInboundCount(): number { return this.inboundEvents.length; }
+
   private handleF0(cmd: Cyw43Cmd, payload: Uint8Array, rxBytes: number): Uint8Array | null {
     if (cmd.write) {
       const word = readU32LE(payload, 0);