xref: /freebsd/share/man/man4/jedec_dimm.4 (revision 6137b5f7b8c183ee8806d79b3f1d8e5e3ddb3df3)
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5.\" Copyright (c) 2018 Ravi Pokala <rpokala@freebsd.org>
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27.Dd April 25, 2023
28.Dt JEDEC_DIMM 4
29.Os
30.Sh NAME
31.Nm jedec_dimm
32.Nd report asset information and temperatures for JEDEC DDR3 / DDR4 DIMMs
33.Sh SYNOPSIS
34.Bd -ragged -offset indent
35.Cd "device jedec_dimm"
36.Cd "device smbus"
37.Ed
38.Pp
39Alternatively, to load the driver as a module at boot time, place the following
40line in
41.Xr loader.conf 5 :
42.Bd -literal -offset indent
43jedec_dimm_load="YES"
44.Ed
45.Pp
46Addressing information must be manually specified in
47.Pa /boot/device.hints :
48.Bd -literal -offset indent
49.Cd hint.jedec_dimm.0.at="smbus0"
50.Cd hint.jedec_dimm.0.addr="0xa0"
51.Cd hint.jedec_dimm.0.slotid="Silkscreen"
52.Ed
53.Sh DESCRIPTION
54The
55.Nm
56driver reports asset information (Part Number, Serial Number) encoded in the
57.Dq Serial Presence Detect
58(SPD) data on JEDEC DDR3 and DDR4 DIMMs.
59It also calculates and reports the memory capacity of the DIMM, in megabytes.
60If the DIMM includes a
61.Dq Thermal Sensor On DIMM
62(TSOD), the temperature is also reported.
63.Pp
64The
65.Nm
66driver accesses the SPD and TSOD over the
67.Xr smbus 4 .
68.Pp
69The data is reported via a
70.Xr sysctl 8
71interface; all values are read-only:
72.Bl -tag -width "dev.jedec_dimm.X.capacity"
73.It Va dev.jedec_dimm.X.%desc
74a string description of the DIMM, including TSOD and slotid info if present.
75.It Va dev.jedec_dimm.X.capacity
76the DIMM's memory capacity, in megabytes
77.It Va dev.jedec_dimm.X.mfg_week
78the week within the year in which the DIMM was manufactured
79.It Va dev.jedec_dimm.X.mfg_year
80the year in which the DIMM was manufactured
81.It Va dev.jedec_dimm.X.part
82the manufacturer's part number of the DIMM
83.It Va dev.jedec_dimm.X.serial
84the manufacturer's serial number of the DIMM
85.It Va dev.jedec_dimm.X.slotid
86a copy of the corresponding hint, if set
87.It Va dev.jedec_dimm.X.temp
88if a TSOD is present, the reported temperature
89.It Va dev.jedec_dimm.X.type
90the DIMM type (DDR3 or DDR4)
91.El
92.Pp
93These values are configurable for
94.Nm
95via
96.Xr device.hints 5 :
97.Bl -tag -width "hint.jedec_dimm.X.slotid"
98.It Va hint.jedec_dimm.X.at
99the
100.Xr smbus 4
101to which the DIMM is connected
102.It Va hint.jedec_dimm.X.addr
103the SMBus address of the SPD.
104JEDEC specifies that the four most-significant bits of the address are the
105.Dq Device Type Identifier
106(DTI), and that the DTI of the SPD is 0xa.
107Since the least-significant bit of an SMBus address is the read/write bit, and
108is always written as 0, that means the four least-significant bits of the
109address must be even.
110.It Va hint.jedec_dimm.X.slotid
111optional slot identifier.
112If populated with the DIMM slot name silkscreened on the motherboard, this
113provides a mapping between the DIMM slot name and the DIMM serial number.
114That mapping is useful for detailed asset tracking, and makes it easier to
115physically locate a specific DIMM when doing a replacement.
116This is useful when assembling multiple identical systems, as might be done by
117a system vendor.
118The mapping between bus/address and DIMM slot must first be determined, either
119through motherboard documentation or trial-and-error.
120.El
121.Pp
122If the DIMMs are on an I2C bus behind an
123.Xr iicbus 4
124controller, then the
125.Xr iicsmb 4
126bridge driver can be used to attach the
127.Xr smbus 4 .
128.Sh EXAMPLES
129Consider two DDR4 DIMMs with the following hints:
130.Bd -literal -offset indent
131hint.jedec_dimm.0.at="smbus0"
132hint.jedec_dimm.0.addr="0xa0"
133hint.jedec_dimm.0.slotid="A1"
134
135hint.jedec_dimm.6.at="smbus1"
136hint.jedec_dimm.6.addr="0xa8"
137.Ed
138.Pp
139Their
140.Xr sysctl 8
141output (sorted):
142.Bd -literal -offset indent
143dev.jedec_dimm.0.%desc: DDR4 DIMM w/ Atmel TSOD (A1)
144dev.jedec_dimm.0.%driver: jedec_dimm
145dev.jedec_dimm.0.%location: addr=0xa0
146dev.jedec_dimm.0.%parent: smbus0
147dev.jedec_dimm.0.%pnpinfo:
148dev.jedec_dimm.0.capacity: 16384
149dev.jedec_dimm.0.mfg_week: 30
150dev.jedec_dimm.0.mfg_year: 17
151dev.jedec_dimm.0.part: 36ASF2G72PZ-2G1A2
152dev.jedec_dimm.0.serial: 0ea815de
153dev.jedec_dimm.0.slotid: A1
154dev.jedec_dimm.0.temp: 32.7C
155dev.jedec_dimm.0.type: DDR4
156
157dev.jedec_dimm.6.%desc: DDR4 DIMM w/ TSE2004av compliant TSOD
158dev.jedec_dimm.6.%driver: jedec_dimm
159dev.jedec_dimm.6.%location: addr=0xa8
160dev.jedec_dimm.6.%parent: smbus1
161dev.jedec_dimm.6.%pnpinfo:
162dev.jedec_dimm.6.capacity: 8192
163dev.jedec_dimm.6.mfg_week: 13
164dev.jedec_dimm.6.mfg_year: 19
165dev.jedec_dimm.6.part: VRA9MR8B2H1603
166dev.jedec_dimm.6.serial: 0c4c46ad
167dev.jedec_dimm.6.temp: 43.1C
168dev.jedec_dimm.6.type: DDR4
169.Ed
170.Sh COMPATIBILITY
171.Nm
172implements a superset of the functionality of the now-deleted
173.Xr jedec_ts 4 .
174Hints for
175.Xr jedec_ts 4
176can be mechanically converted for use with
177.Nm .
178Two changes are required:
179.Bl -enum
180.It
181In all
182.Xr jedec_ts 4
183hints, replace
184.Dq jedec_ts
185with
186.Dq jedec_dimm
187.It
188In
189.Xr jedec_ts 4
190.Dq addr
191hints, replace the TSOD DTI
192.Dq 0x3
193with the SPD DTI
194.Dq 0xa
195.El
196.Pp
197The following
198.Xr sed 1
199script will perform the necessary changes:
200.Bd -literal -offset indent
201sed -i ".old" -e 's/jedec_ts/jedec_dimm/' \\
202    -e '/jedec_dimm/s/addr="0x3/addr="0xa/' /boot/device.hints
203.Ed
204.Sh SEE ALSO
205.Xr iicbus 4 ,
206.Xr iicsmb 4 ,
207.Xr smbus 4 ,
208.Xr sysctl 8
209.Sh STANDARDS
210.Rs
211(DDR3 SPD)
212.%A JEDEC
213.%T Standard 21-C, Annex K
214.Re
215.Pp
216.Rs
217(DDR3 TSOD)
218.%A JEDEC
219.%T Standard 21-C, TSE2002av
220.Re
221.Pp
222.Rs
223(DDR4 SPD)
224.%A JEDEC
225.%T Standard 21-C, Annex L
226.Re
227.Pp
228.Rs
229(DDR4 TSOD)
230.%A JEDEC
231.%T Standard 21-C, TSE2004av
232.Re
233.Sh HISTORY
234The
235.Nm
236driver first appeared in
237.Fx 12.0 .
238.Sh AUTHORS
239.An -nosplit
240The
241.Nm
242driver and this manual page were written by
243.An Ravi Pokala Aq Mt rpokala@freebsd.org .
244They are both based in part on the now-deleted
245.Xr jedec_ts 4
246driver and manual page, written by
247.An Andriy Gapon Aq Mt avg@FreeBSD.org .
248