IB/ipath: Log "active" time and some errors to EEPROM

We currently track various errors, now we enhance that capability by
logging some of them to EEPROM.  We also now log a cumulative "active"
time defined by traffic though the InfiniPath HCA beyond the normal SM
traffic.
Signed-off-by: Michael Albaugh <michael.albaugh@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_driver.c

@@ -2005,6 +2005,9 @@ void ipath_shutdown_device(struct ipath_devdata *dd)
 			 ~0ULL & ~INFINIPATH_HWE_MEMBISTFAILED);
 	ipath_write_kreg(dd, dd->ipath_kregs->kr_errorclear, -1LL);
 	ipath_write_kreg(dd, dd->ipath_kregs->kr_intclear, -1LL);
+
+	ipath_cdbg(VERBOSE, "Flush time and errors to EEPROM\n");
+	ipath_update_eeprom_log(dd);
 }
 
 /**

drivers/infiniband/hw/ipath/ipath_eeprom.c

@@ -367,8 +367,8 @@ static int eeprom_reset(struct ipath_devdata *dd)
  * @len: number of bytes to receive
  */
 
-int ipath_eeprom_read(struct ipath_devdata *dd, u8 eeprom_offset,
-		      void *buffer, int len)
+static int ipath_eeprom_internal_read(struct ipath_devdata *dd,
+					u8 eeprom_offset, void *buffer, int len)
 {
 	/* compiler complains unless initialized */
 	u8 single_byte = 0;
@@ -418,6 +418,7 @@ int ipath_eeprom_read(struct ipath_devdata *dd, u8 eeprom_offset,
 	return ret;
 }
 
+
 /**
  * ipath_eeprom_write - writes data to the eeprom via I2C
  * @dd: the infinipath device
@@ -425,7 +426,7 @@ int ipath_eeprom_read(struct ipath_devdata *dd, u8 eeprom_offset,
  * @buffer: data to write
  * @len: number of bytes to write
  */
-int ipath_eeprom_write(struct ipath_devdata *dd, u8 eeprom_offset,
+int ipath_eeprom_internal_write(struct ipath_devdata *dd, u8 eeprom_offset,
 				const void *buffer, int len)
 {
 	u8 single_byte;
@@ -500,6 +501,38 @@ int ipath_eeprom_write(struct ipath_devdata *dd, u8 eeprom_offset,
 	return ret;
 }
 
+/*
+ * The public entry-points ipath_eeprom_read() and ipath_eeprom_write()
+ * are now just wrappers around the internal functions.
+ */
+int ipath_eeprom_read(struct ipath_devdata *dd, u8 eeprom_offset,
+			void *buff, int len)
+{
+	int ret;
+
+	ret = down_interruptible(&dd->ipath_eep_sem);
+	if (!ret) {
+		ret = ipath_eeprom_internal_read(dd, eeprom_offset, buff, len);
+		up(&dd->ipath_eep_sem);
+	}
+
+	return ret;
+}
+
+int ipath_eeprom_write(struct ipath_devdata *dd, u8 eeprom_offset,
+			const void *buff, int len)
+{
+	int ret;
+
+	ret = down_interruptible(&dd->ipath_eep_sem);
+	if (!ret) {
+		ret = ipath_eeprom_internal_write(dd, eeprom_offset, buff, len);
+		up(&dd->ipath_eep_sem);
+	}
+
+	return ret;
+}
+
 static u8 flash_csum(struct ipath_flash *ifp, int adjust)
 {
 	u8 *ip = (u8 *) ifp;
@@ -527,7 +560,7 @@ void ipath_get_eeprom_info(struct ipath_devdata *dd)
 	void *buf;
 	struct ipath_flash *ifp;
 	__be64 guid;
-	int len;
+	int len, eep_stat;
 	u8 csum, *bguid;
 	int t = dd->ipath_unit;
 	struct ipath_devdata *dd0 = ipath_lookup(0);
@@ -571,7 +604,11 @@ void ipath_get_eeprom_info(struct ipath_devdata *dd)
 		goto bail;
 	}
 
-	if (ipath_eeprom_read(dd, 0, buf, len)) {
+	down(&dd->ipath_eep_sem);
+	eep_stat = ipath_eeprom_internal_read(dd, 0, buf, len);
+	up(&dd->ipath_eep_sem);
+
+	if (eep_stat) {
 		ipath_dev_err(dd, "Failed reading GUID from eeprom\n");
 		goto done;
 	}
@@ -646,8 +683,192 @@ void ipath_get_eeprom_info(struct ipath_devdata *dd)
 	ipath_cdbg(VERBOSE, "Initted GUID to %llx from eeprom\n",
 		   (unsigned long long) be64_to_cpu(dd->ipath_guid));
 
+	memcpy(&dd->ipath_eep_st_errs, &ifp->if_errcntp, IPATH_EEP_LOG_CNT);
+	/*
+	 * Power-on (actually "active") hours are kept as little-endian value
+	 * in EEPROM, but as seconds in a (possibly as small as 24-bit)
+	 * atomic_t while running.
+	 */
+	atomic_set(&dd->ipath_active_time, 0);
+	dd->ipath_eep_hrs = ifp->if_powerhour[0] | (ifp->if_powerhour[1] << 8);
+
 done:
 	vfree(buf);
 
 bail:;
 }
+
+/**
+ * ipath_update_eeprom_log - copy active-time and error counters to eeprom
+ * @dd: the infinipath device
+ *
+ * Although the time is kept as seconds in the ipath_devdata struct, it is
+ * rounded to hours for re-write, as we have only 16 bits in EEPROM.
+ * First-cut code reads whole (expected) struct ipath_flash, modifies,
+ * re-writes. Future direction: read/write only what we need, assuming
+ * that the EEPROM had to have been "good enough" for driver init, and
+ * if not, we aren't making it worse.
+ *
+ */
+
+int ipath_update_eeprom_log(struct ipath_devdata *dd)
+{
+	void *buf;
+	struct ipath_flash *ifp;
+	int len, hi_water;
+	uint32_t new_time, new_hrs;
+	u8 csum;
+	int ret, idx;
+	unsigned long flags;
+
+	/* first, check if we actually need to do anything. */
+	ret = 0;
+	for (idx = 0; idx < IPATH_EEP_LOG_CNT; ++idx) {
+		if (dd->ipath_eep_st_new_errs[idx]) {
+			ret = 1;
+			break;
+		}
+	}
+	new_time = atomic_read(&dd->ipath_active_time);
+
+	if (ret == 0 && new_time < 3600)
+		return 0;
+
+	/*
+	 * The quick-check above determined that there is something worthy
+	 * of logging, so get current contents and do a more detailed idea.
+	 */
+	len = offsetof(struct ipath_flash, if_future);
+	buf = vmalloc(len);
+	ret = 1;
+	if (!buf) {
+		ipath_dev_err(dd, "Couldn't allocate memory to read %u "
+				"bytes from eeprom for logging\n", len);
+		goto bail;
+	}
+
+	/* Grab semaphore and read current EEPROM. If we get an
+	 * error, let go, but if not, keep it until we finish write.
+	 */
+	ret = down_interruptible(&dd->ipath_eep_sem);
+	if (ret) {
+		ipath_dev_err(dd, "Unable to acquire EEPROM for logging\n");
+		goto free_bail;
+	}
+	ret = ipath_eeprom_internal_read(dd, 0, buf, len);
+	if (ret) {
+		up(&dd->ipath_eep_sem);
+		ipath_dev_err(dd, "Unable read EEPROM for logging\n");
+		goto free_bail;
+	}
+	ifp = (struct ipath_flash *)buf;
+
+	csum = flash_csum(ifp, 0);
+	if (csum != ifp->if_csum) {
+		up(&dd->ipath_eep_sem);
+		ipath_dev_err(dd, "EEPROM cks err (0x%02X, S/B 0x%02X)\n",
+				csum, ifp->if_csum);
+		ret = 1;
+		goto free_bail;
+	}
+	hi_water = 0;
+	spin_lock_irqsave(&dd->ipath_eep_st_lock, flags);
+	for (idx = 0; idx < IPATH_EEP_LOG_CNT; ++idx) {
+		int new_val = dd->ipath_eep_st_new_errs[idx];
+		if (new_val) {
+			/*
+			 * If we have seen any errors, add to EEPROM values
+			 * We need to saturate at 0xFF (255) and we also
+			 * would need to adjust the checksum if we were
+			 * trying to minimize EEPROM traffic
+			 * Note that we add to actual current count in EEPROM,
+			 * in case it was altered while we were running.
+			 */
+			new_val += ifp->if_errcntp[idx];
+			if (new_val > 0xFF)
+				new_val = 0xFF;
+			if (ifp->if_errcntp[idx] != new_val) {
+				ifp->if_errcntp[idx] = new_val;
+				hi_water = offsetof(struct ipath_flash,
+						if_errcntp) + idx;
+			}
+			/*
+			 * update our shadow (used to minimize EEPROM
+			 * traffic), to match what we are about to write.
+			 */
+			dd->ipath_eep_st_errs[idx] = new_val;
+			dd->ipath_eep_st_new_errs[idx] = 0;
+		}
+	}
+	/*
+	 * now update active-time. We would like to round to the nearest hour
+	 * but unless atomic_t are sure to be proper signed ints we cannot,
+	 * because we need to account for what we "transfer" to EEPROM and
+	 * if we log an hour at 31 minutes, then we would need to set
+	 * active_time to -29 to accurately count the _next_ hour.
+	 */
+	if (new_time > 3600) {
+		new_hrs = new_time / 3600;
+		atomic_sub((new_hrs * 3600), &dd->ipath_active_time);
+		new_hrs += dd->ipath_eep_hrs;
+		if (new_hrs > 0xFFFF)
+			new_hrs = 0xFFFF;
+		dd->ipath_eep_hrs = new_hrs;
+		if ((new_hrs & 0xFF) != ifp->if_powerhour[0]) {
+			ifp->if_powerhour[0] = new_hrs & 0xFF;
+			hi_water = offsetof(struct ipath_flash, if_powerhour);
+		}
+		if ((new_hrs >> 8) != ifp->if_powerhour[1]) {
+			ifp->if_powerhour[1] = new_hrs >> 8;
+			hi_water = offsetof(struct ipath_flash, if_powerhour)
+					+ 1;
+		}
+	}
+	/*
+	 * There is a tiny possibility that we could somehow fail to write
+	 * the EEPROM after updating our shadows, but problems from holding
+	 * the spinlock too long are a much bigger issue.
+	 */
+	spin_unlock_irqrestore(&dd->ipath_eep_st_lock, flags);
+	if (hi_water) {
+		/* we made some change to the data, uopdate cksum and write */
+		csum = flash_csum(ifp, 1);
+		ret = ipath_eeprom_internal_write(dd, 0, buf, hi_water + 1);
+	}
+	up(&dd->ipath_eep_sem);
+	if (ret)
+		ipath_dev_err(dd, "Failed updating EEPROM\n");
+
+free_bail:
+	vfree(buf);
+bail:
+	return ret;
+
+}
+
+/**
+ * ipath_inc_eeprom_err - increment one of the four error counters
+ * that are logged to EEPROM.
+ * @dd: the infinipath device
+ * @eidx: 0..3, the counter to increment
+ * @incr: how much to add
+ *
+ * Each counter is 8-bits, and saturates at 255 (0xFF). They
+ * are copied to the EEPROM (aka flash) whenever ipath_update_eeprom_log()
+ * is called, but it can only be called in a context that allows sleep.
+ * This function can be called even at interrupt level.
+ */
+
+void ipath_inc_eeprom_err(struct ipath_devdata *dd, u32 eidx, u32 incr)
+{
+	uint new_val;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dd->ipath_eep_st_lock, flags);
+	new_val = dd->ipath_eep_st_new_errs[eidx] + incr;
+	if (new_val > 255)
+		new_val = 255;
+	dd->ipath_eep_st_new_errs[eidx] = new_val;
+	spin_unlock_irqrestore(&dd->ipath_eep_st_lock, flags);
+	return;
+}

drivers/infiniband/hw/ipath/ipath_iba6110.c

@@ -440,6 +440,7 @@ static void ipath_ht_handle_hwerrors(struct ipath_devdata *dd, char *msg,
 	u32 bits, ctrl;
 	int isfatal = 0;
 	char bitsmsg[64];
+	int log_idx;
 
 	hwerrs = ipath_read_kreg64(dd, dd->ipath_kregs->kr_hwerrstatus);
 
@@ -468,6 +469,11 @@ static void ipath_ht_handle_hwerrors(struct ipath_devdata *dd, char *msg,
 
 	hwerrs &= dd->ipath_hwerrmask;
 
+	/* We log some errors to EEPROM, check if we have any of those. */
+	for (log_idx = 0; log_idx < IPATH_EEP_LOG_CNT; ++log_idx)
+		if (hwerrs & dd->ipath_eep_st_masks[log_idx].hwerrs_to_log)
+			ipath_inc_eeprom_err(dd, log_idx, 1);
+
 	/*
 	 * make sure we get this much out, unless told to be quiet,
 	 * it's a parity error we may recover from,
@@ -1171,6 +1177,22 @@ static void ipath_init_ht_variables(struct ipath_devdata *dd)
 
 	dd->ipath_i_rcvavail_mask = INFINIPATH_I_RCVAVAIL_MASK;
 	dd->ipath_i_rcvurg_mask = INFINIPATH_I_RCVURG_MASK;
+
+	/*
+	 * EEPROM error log 0 is TXE Parity errors. 1 is RXE Parity.
+	 * 2 is Some Misc, 3 is reserved for future.
+	 */
+	dd->ipath_eep_st_masks[0].hwerrs_to_log =
+		INFINIPATH_HWE_TXEMEMPARITYERR_MASK <<
+		INFINIPATH_HWE_TXEMEMPARITYERR_SHIFT;
+
+	dd->ipath_eep_st_masks[1].hwerrs_to_log =
+		INFINIPATH_HWE_RXEMEMPARITYERR_MASK <<
+		INFINIPATH_HWE_RXEMEMPARITYERR_SHIFT;
+
+	dd->ipath_eep_st_masks[2].errs_to_log =
+		INFINIPATH_E_INVALIDADDR | INFINIPATH_E_RESET;
+
 }
 
 /**

drivers/infiniband/hw/ipath/ipath_iba6120.c

@@ -340,6 +340,7 @@ static void ipath_pe_handle_hwerrors(struct ipath_devdata *dd, char *msg,
 	u32 bits, ctrl;
 	int isfatal = 0;
 	char bitsmsg[64];
+	int log_idx;
 
 	hwerrs = ipath_read_kreg64(dd, dd->ipath_kregs->kr_hwerrstatus);
 	if (!hwerrs) {
@@ -367,6 +368,11 @@ static void ipath_pe_handle_hwerrors(struct ipath_devdata *dd, char *msg,
 
 	hwerrs &= dd->ipath_hwerrmask;
 
+	/* We log some errors to EEPROM, check if we have any of those. */
+	for (log_idx = 0; log_idx < IPATH_EEP_LOG_CNT; ++log_idx)
+		if (hwerrs & dd->ipath_eep_st_masks[log_idx].hwerrs_to_log)
+			ipath_inc_eeprom_err(dd, log_idx, 1);
+
 	/*
 	 * make sure we get this much out, unless told to be quiet,
 	 * or it's occurred within the last 5 seconds
@@ -950,6 +956,27 @@ static void ipath_init_pe_variables(struct ipath_devdata *dd)
 
 	dd->ipath_i_rcvavail_mask = INFINIPATH_I_RCVAVAIL_MASK;
 	dd->ipath_i_rcvurg_mask = INFINIPATH_I_RCVURG_MASK;
+
+	/*
+	 * EEPROM error log 0 is TXE Parity errors. 1 is RXE Parity.
+	 * 2 is Some Misc, 3 is reserved for future.
+	 */
+	dd->ipath_eep_st_masks[0].hwerrs_to_log =
+		INFINIPATH_HWE_TXEMEMPARITYERR_MASK <<
+		INFINIPATH_HWE_TXEMEMPARITYERR_SHIFT;
+
+	/* Ignore errors in PIO/PBC on systems with unordered write-combining */
+	if (ipath_unordered_wc())
+		dd->ipath_eep_st_masks[0].hwerrs_to_log &= ~TXE_PIO_PARITY;
+
+	dd->ipath_eep_st_masks[1].hwerrs_to_log =
+		INFINIPATH_HWE_RXEMEMPARITYERR_MASK <<
+		INFINIPATH_HWE_RXEMEMPARITYERR_SHIFT;
+
+	dd->ipath_eep_st_masks[2].errs_to_log =
+		INFINIPATH_E_INVALIDADDR | INFINIPATH_E_RESET;
+
+
 }
 
 /* setup the MSI stuff again after a reset.  I'd like to just call

drivers/infiniband/hw/ipath/ipath_init_chip.c

@@ -341,6 +341,8 @@ static int init_chip_first(struct ipath_devdata *dd,
 	spin_lock_init(&dd->ipath_tid_lock);
 
 	spin_lock_init(&dd->ipath_gpio_lock);
+	spin_lock_init(&dd->ipath_eep_st_lock);
+	sema_init(&dd->ipath_eep_sem, 1);
 
 done:
 	*pdp = pd;

drivers/infiniband/hw/ipath/ipath_intr.c

@@ -505,6 +505,7 @@ static int handle_errors(struct ipath_devdata *dd, ipath_err_t errs)
 	int i, iserr = 0;
 	int chkerrpkts = 0, noprint = 0;
 	unsigned supp_msgs;
+	int log_idx;
 
 	supp_msgs = handle_frequent_errors(dd, errs, msg, &noprint);
 
@@ -518,6 +519,13 @@ static int handle_errors(struct ipath_devdata *dd, ipath_err_t errs)
 	if (errs & INFINIPATH_E_HARDWARE) {
 		/* reuse same msg buf */
 		dd->ipath_f_handle_hwerrors(dd, msg, sizeof msg);
+	} else {
+		u64 mask;
+		for (log_idx = 0; log_idx < IPATH_EEP_LOG_CNT; ++log_idx) {
+			mask = dd->ipath_eep_st_masks[log_idx].errs_to_log;
+			if (errs & mask)
+				ipath_inc_eeprom_err(dd, log_idx, 1);
+		}
 	}
 
 	if (!noprint && (errs & ~dd->ipath_e_bitsextant))

drivers/infiniband/hw/ipath/ipath_kernel.h

@@ -57,6 +57,24 @@
 extern struct infinipath_stats ipath_stats;
 
 #define IPATH_CHIP_SWVERSION IPATH_CHIP_VERS_MAJ
+/*
+ * First-cut critierion for "device is active" is
+ * two thousand dwords combined Tx, Rx traffic per
+ * 5-second interval. SMA packets are 64 dwords,
+ * and occur "a few per second", presumably each way.
+ */
+#define IPATH_TRAFFIC_ACTIVE_THRESHOLD (2000)
+/*
+ * Struct used to indicate which errors are logged in each of the
+ * error-counters that are logged to EEPROM. A counter is incremented
+ * _once_ (saturating at 255) for each event with any bits set in
+ * the error or hwerror register masks below.
+ */
+#define IPATH_EEP_LOG_CNT (4)
+struct ipath_eep_log_mask {
+	u64 errs_to_log;
+	u64 hwerrs_to_log;
+};
 
 struct ipath_portdata {
 	void **port_rcvegrbuf;
@@ -588,6 +606,24 @@ struct ipath_devdata {
 	/* Used to flash LEDs in override mode */
 	struct timer_list ipath_led_override_timer;
 
+	/* Support (including locks) for EEPROM logging of errors and time */
+	/* control access to actual counters, timer */
+	spinlock_t ipath_eep_st_lock;
+	/* control high-level access to EEPROM */
+	struct semaphore ipath_eep_sem;
+	/* Below inc'd by ipath_snap_cntrs(), locked by ipath_eep_st_lock */
+	uint64_t ipath_traffic_wds;
+	/* active time is kept in seconds, but logged in hours */
+	atomic_t ipath_active_time;
+	/* Below are nominal shadow of EEPROM, new since last EEPROM update */
+	uint8_t ipath_eep_st_errs[IPATH_EEP_LOG_CNT];
+	uint8_t ipath_eep_st_new_errs[IPATH_EEP_LOG_CNT];
+	uint16_t ipath_eep_hrs;
+	/*
+	 * masks for which bits of errs, hwerrs that cause
+	 * each of the counters to increment.
+	 */
+	struct ipath_eep_log_mask ipath_eep_st_masks[IPATH_EEP_LOG_CNT];
 };
 
 /* Private data for file operations */
@@ -726,6 +762,8 @@ u32 __iomem *ipath_getpiobuf(struct ipath_devdata *, u32 *);
 void ipath_init_iba6120_funcs(struct ipath_devdata *);
 void ipath_init_iba6110_funcs(struct ipath_devdata *);
 void ipath_get_eeprom_info(struct ipath_devdata *);
+int ipath_update_eeprom_log(struct ipath_devdata *dd);
+void ipath_inc_eeprom_err(struct ipath_devdata *dd, u32 eidx, u32 incr);
 u64 ipath_snap_cntr(struct ipath_devdata *, ipath_creg);
 void ipath_disarm_senderrbufs(struct ipath_devdata *, int);
 

drivers/infiniband/hw/ipath/ipath_stats.c

@@ -55,6 +55,7 @@ u64 ipath_snap_cntr(struct ipath_devdata *dd, ipath_creg creg)
 	u64 val64;
 	unsigned long t0, t1;
 	u64 ret;
+	unsigned long flags;
 
 	t0 = jiffies;
 	/* If fast increment counters are only 32 bits, snapshot them,
@@ -91,12 +92,18 @@ u64 ipath_snap_cntr(struct ipath_devdata *dd, ipath_creg creg)
 	if (creg == dd->ipath_cregs->cr_wordsendcnt) {
 		if (val != dd->ipath_lastsword) {
 			dd->ipath_sword += val - dd->ipath_lastsword;
+			spin_lock_irqsave(&dd->ipath_eep_st_lock, flags);
+			dd->ipath_traffic_wds += val - dd->ipath_lastsword;
+			spin_unlock_irqrestore(&dd->ipath_eep_st_lock, flags);
 			dd->ipath_lastsword = val;
 		}
 		val64 = dd->ipath_sword;
 	} else if (creg == dd->ipath_cregs->cr_wordrcvcnt) {
 		if (val != dd->ipath_lastrword) {
 			dd->ipath_rword += val - dd->ipath_lastrword;
+			spin_lock_irqsave(&dd->ipath_eep_st_lock, flags);
+			dd->ipath_traffic_wds += val - dd->ipath_lastrword;
+			spin_unlock_irqrestore(&dd->ipath_eep_st_lock, flags);
 			dd->ipath_lastrword = val;
 		}
 		val64 = dd->ipath_rword;
@@ -200,6 +207,7 @@ void ipath_get_faststats(unsigned long opaque)
 	struct ipath_devdata *dd = (struct ipath_devdata *) opaque;
 	u32 val;
 	static unsigned cnt;
+	unsigned long flags;
 
 	/*
 	 * don't access the chip while running diags, or memory diags can
@@ -210,9 +218,20 @@ void ipath_get_faststats(unsigned long opaque)
 		/* but re-arm the timer, for diags case; won't hurt other */
 		goto done;
 
-	if (dd->ipath_flags & IPATH_32BITCOUNTERS) {
+	/*
+	 * We now try to maintain a "active timer", based on traffic
+	 * exceeding a threshold, so we need to check the word-counts
+	 * even if they are 64-bit.
+	 */
 	ipath_snap_cntr(dd, dd->ipath_cregs->cr_wordsendcnt);
 	ipath_snap_cntr(dd, dd->ipath_cregs->cr_wordrcvcnt);
+	spin_lock_irqsave(&dd->ipath_eep_st_lock, flags);
+	if (dd->ipath_traffic_wds  >= IPATH_TRAFFIC_ACTIVE_THRESHOLD)
+		atomic_add(5, &dd->ipath_active_time); /* S/B #define */
+	dd->ipath_traffic_wds = 0;
+	spin_unlock_irqrestore(&dd->ipath_eep_st_lock, flags);
+
+	if (dd->ipath_flags & IPATH_32BITCOUNTERS) {
 		ipath_snap_cntr(dd, dd->ipath_cregs->cr_pktsendcnt);
 		ipath_snap_cntr(dd, dd->ipath_cregs->cr_pktrcvcnt);
 	}

drivers/infiniband/hw/ipath/ipath_sysfs.c

@@ -613,6 +613,26 @@ static ssize_t store_led_override(struct device *dev,
 	return ret;
 }
 
+static ssize_t show_logged_errs(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct ipath_devdata *dd = dev_get_drvdata(dev);
+	int idx, count;
+
+	/* force consistency with actual EEPROM */
+	if (ipath_update_eeprom_log(dd) != 0)
+		return -ENXIO;
+
+	count = 0;
+	for (idx = 0; idx < IPATH_EEP_LOG_CNT; ++idx) {
+		count += scnprintf(buf + count, PAGE_SIZE - count, "%d%c",
+			dd->ipath_eep_st_errs[idx],
+			idx == (IPATH_EEP_LOG_CNT - 1) ? '\n' : ' ');
+	}
+
+	return count;
+}
 
 static DRIVER_ATTR(num_units, S_IRUGO, show_num_units, NULL);
 static DRIVER_ATTR(version, S_IRUGO, show_version, NULL);
@@ -643,6 +663,7 @@ static DEVICE_ATTR(boardversion, S_IRUGO, show_boardversion, NULL);
 static DEVICE_ATTR(unit, S_IRUGO, show_unit, NULL);
 static DEVICE_ATTR(rx_pol_inv, S_IWUSR, NULL, store_rx_pol_inv);
 static DEVICE_ATTR(led_override, S_IWUSR, NULL, store_led_override);
+static DEVICE_ATTR(logged_errors, S_IRUGO, show_logged_errs, NULL);
 
 static struct attribute *dev_attributes[] = {
 	&dev_attr_guid.attr,
@@ -660,6 +681,7 @@ static struct attribute *dev_attributes[] = {
 	&dev_attr_enabled.attr,
 	&dev_attr_rx_pol_inv.attr,
 	&dev_attr_led_override.attr,
+	&dev_attr_logged_errors.attr,
 	NULL
 };