IB/ipath: Add capability to modify PBC word

During compliance testing and when debugging some interconnect issues,
it is very useful to be able to send malformed packets, without having
the device signal them as malformed (drop, or terminate with EBP). The
hardware supports this, but the driver "diagnostic packet" interface
did not.

Extend capability to send specific malformed packets for testing.
Signed-off-by: Michael Albaugh <Michael.Albaugh@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_common.h

@@ -501,13 +501,30 @@ struct __ipath_sendpkt {
 	struct ipath_iovec sps_iov[4];
 };
 
-/* Passed into diag data special file's ->write method. */
+/*
+ * diagnostics can send a packet by "writing" one of the following
+ * two structs to diag data special file
+ * The first is the legacy version for backward compatibility
+ */
 struct ipath_diag_pkt {
 	__u32 unit;
 	__u64 data;
 	__u32 len;
 };
 
+/* The second diag_pkt struct is the expanded version that allows
+ * more control over the packet, specifically, by allowing a custom
+ * pbc (+ extra) qword, so that special modes and deliberate
+ * changes to CRCs can be used. The elements were also re-ordered
+ * for better alignment and to avoid padding issues.
+ */
+struct ipath_diag_xpkt {
+	__u64 data;
+	__u64 pbc_wd;
+	__u32 unit;
+	__u32 len;
+};
+
 /*
  * Data layout in I2C flash (for GUID, etc.)
  * All fields are little-endian binary unless otherwise stated

drivers/infiniband/hw/ipath/ipath_diag.c

@@ -323,13 +323,14 @@ static ssize_t ipath_diagpkt_write(struct file *fp,
 {
 	u32 __iomem *piobuf;
 	u32 plen, clen, pbufn;
-	struct ipath_diag_pkt dp;
+	struct ipath_diag_pkt odp;
+	struct ipath_diag_xpkt dp;
 	u32 *tmpbuf = NULL;
 	struct ipath_devdata *dd;
 	ssize_t ret = 0;
 	u64 val;
 
-	if (count < sizeof(dp)) {
+	if (count != sizeof(dp)) {
 		ret = -EINVAL;
 		goto bail;
 	}
@@ -339,6 +340,29 @@ static ssize_t ipath_diagpkt_write(struct file *fp,
 		goto bail;
 	}
 
+	/*
+	 * Due to padding/alignment issues (lessened with new struct)
+	 * the old and new structs are the same length. We need to
+	 * disambiguate them, which we can do because odp.len has never
+	 * been less than the total of LRH+BTH+DETH so far, while
+	 * dp.unit (same offset) unit is unlikely to get that high.
+	 * Similarly, dp.data, the pointer to user at the same offset
+	 * as odp.unit, is almost certainly at least one (512byte)page
+	 * "above" NULL. The if-block below can be omitted if compatibility
+	 * between a new driver and older diagnostic code is unimportant.
+	 * compatibility the other direction (new diags, old driver) is
+	 * handled in the diagnostic code, with a warning.
+	 */
+	if (dp.unit >= 20 && dp.data < 512) {
+		/* very probable version mismatch. Fix it up */
+		memcpy(&odp, &dp, sizeof(odp));
+		/* We got a legacy dp, copy elements to dp */
+		dp.unit = odp.unit;
+		dp.data = odp.data;
+		dp.len = odp.len;
+		dp.pbc_wd = 0; /* Indicate we need to compute PBC wd */
+	}
+
 	/* send count must be an exact number of dwords */
 	if (dp.len & 3) {
 		ret = -EINVAL;
@@ -371,9 +395,10 @@ static ssize_t ipath_diagpkt_write(struct file *fp,
 		ret = -ENODEV;
 		goto bail;
 	}
+	/* Check link state, but not if we have custom PBC */
 	val = dd->ipath_lastibcstat & IPATH_IBSTATE_MASK;
-	if (val != IPATH_IBSTATE_INIT && val != IPATH_IBSTATE_ARM &&
-	    val != IPATH_IBSTATE_ACTIVE) {
+	if (!dp.pbc_wd && val != IPATH_IBSTATE_INIT &&
+		val != IPATH_IBSTATE_ARM && val != IPATH_IBSTATE_ACTIVE) {
 		ipath_cdbg(VERBOSE, "unit %u not ready (state %llx)\n",
 			   dd->ipath_unit, (unsigned long long) val);
 		ret = -EINVAL;
@@ -419,9 +444,13 @@ static ssize_t ipath_diagpkt_write(struct file *fp,
 		ipath_cdbg(VERBOSE, "unit %u 0x%x+1w pio%d\n",
 			   dd->ipath_unit, plen - 1, pbufn);
 
+	if (dp.pbc_wd == 0)
+		/* Legacy operation, use computed pbc_wd */
+		dp.pbc_wd = plen;
+
 	/* we have to flush after the PBC for correctness on some cpus
 	 * or WC buffer can be written out of order */
-	writeq(plen, piobuf);
+	writeq(dp.pbc_wd, piobuf);
 	ipath_flush_wc();
 	/* copy all by the trigger word, then flush, so it's written
 	 * to chip before trigger word, then write trigger word, then