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Index: sys/dev/jedec_dimm/jedec_dimm.c
===================================================================
--- sys/dev/jedec_dimm/jedec_dimm.c
+++ sys/dev/jedec_dimm/jedec_dimm.c
@@ -270,12 +270,16 @@
}
/* The MSBit of the TSOD-presence byte reports whether or not the TSOD
- * is in fact present. If it is, read manufacturer and device info from
- * it to confirm that it's a valid TSOD device. It's an error if any of
- * those bytes are unreadable; it's not an error if the device is simply
- * not known to us (tsod_match == NULL).
- * While DDR3 and DDR4 don't explicitly require a TSOD, essentially all
- * DDR3 and DDR4 DIMMs include one.
+ * is in fact present. (While DDR3 and DDR4 don't explicitly require a
+ * TSOD, essentially all DDR3 and DDR4 DIMMs include one.) But, as
+ * discussed in [PR 235944], it turns out that some DIMMs claim to have
+ * a TSOD when they actually don't. (Or maybe the firmware blocks it?)
+ * <sigh>
+ * If the SPD data says the TSOD is present, try to read manufacturer
+ * and device info from it to confirm that it's a valid TSOD device.
+ * If the data is unreadable, just continue as if the TSOD isn't there.
+ * If the data was read successfully, see if it is a known TSOD device;
+ * it's okay if it isn't (tsod_match == NULL).
*/
rc = smbus_readb(sc->smbus, sc->spd_addr, tsod_present_offset, &byte);
if (rc != 0) {
@@ -289,12 +293,14 @@
if (rc != 0) {
device_printf(dev,
"failed to read TSOD Manufacturer ID\n");
- goto out;
+ rc = 0;
+ goto no_tsod;
}
rc = jedec_dimm_readw_be(sc, TSOD_REG_DEV_REV, &devid);
if (rc != 0) {
device_printf(dev, "failed to read TSOD Device ID\n");
- goto out;
+ rc = 0;
+ goto no_tsod;
}
tsod_match = jedec_dimm_tsod_match(vendorid, devid);
@@ -309,6 +315,7 @@
}
}
} else {
+no_tsod:
tsod_match = NULL;
tsod_present = false;
}
@@ -621,9 +628,12 @@
rc = smbus_writeb(sc->smbus,
(JEDEC_DTI_PAGE | JEDEC_LSA_PAGE_SET1), 0, 0);
if (rc != 0) {
+ /* Some SPD devices (or SMBus controllers?) claim the
+ * page-change command failed when it actually
+ * succeeded. Log a message but soldier on.
+ */
device_printf(sc->dev, "unable to change page: %d\n",
rc);
- goto out;
}
/* Add 256 to the store location, because we're in the second
* page.

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