0992bdf4aca9d5c9829919873cd02cc7493005bf
6
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Simone
|
694ed6a712 |
i2c-imc-skylake: instantiate the SPD EEPROMs at probe
Call i2c_register_spd() per adapter, like i801 and piix4, instead of
telling the user to echo into new_device. The helper counts populated
slots from DMI and probes upwards from 0x50 via i2c_new_scanned_device(),
so it claims no address that does not answer; each channel carries half
the DIMMs and the scan is per adapter, so each finds its own. Verified:
four clients on load, two per channel, none on the empty slots, and
decode-dimms works with no manual step.
This needed Receive Byte to be worth doing — without I2C_FUNC_SMBUS_BYTE
ee1004 would not have bound to what was instantiated.
The write_disable variant is deliberate. This part is DDR4 only, where
the two are equivalent (the split gates spd5118 on DDR5), and of two
equivalent calls the one that does not read as "this driver enables SPD
writes" is the better name to leave in a driver whose bus is the memory
bus. In-tree convention is write_enable; the cover letter offers to
switch.
Kconfig gains select I2C_SMBUS.
Out-of-tree, compat.h maps the call onto the older unsplit
i2c_register_spd() where that is what the target kernel has. It is force
included from the Makefile so i2c-imc-skylake.c stays byte-identical to
the submitted file, and the Makefile detects the API by grepping the
target kernel's header rather than testing a version number, which keeps
it correct on backported trees. Builds clean against both 6.8 and 7.0
headers; DKMS 1.0.2 installs on all four kernels here.
test-smoke.sh needed two fixes to keep testing what it claims:
- A bound driver owns its address, so the raw transaction checks lost
the SPDs the moment the driver started instantiating them. The script
now unbinds ee1004 for the duration rather than deleting the clients:
sysfs delete_device only removes clients that new_device created,
and unbinding is sufficient because i2c-dev refuses an address only
while a driver is bound (i2cdev_check: `return dev->driver ? -EBUSY
: 0`). Rebound from an EXIT trap.
- Those checks were guarded on an SPD address having been found, and
when the lookup failed they vanished from the run silently: the suite
reported "12 passed, 0 failed" while seven checks had not executed.
Skipped checks are now counted and printed, which is how the above
was noticed at all.
Smoke suite: 20 passed, 0 failed, 0 skipped. checkpatch --strict 0/0/0,
in-tree W=1 and Sparse clean.
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|
Simone
|
c04e0ec5a8 |
i2c-imc-skylake: implement Receive Byte and Send Byte
The engine encodes an address-only transaction in command word bit 18, which is what SMBus Receive Byte and Send Byte need and what was missing for ee1004 to bind. The bit is not documented for the PCU function. It was located by structure rather than by sweeping: SMBCMD on the iMC channel function (datasheet ref. 614073 section 3.1.8) places PNTR_SEL immediately above WORD_ACCESS, and word access here is bit 17. Bit 17 had itself been unknown until it turned out to be word access, and an earlier sweep of this register covered bits 31:20 only, so 18 was untried rather than already ruled out. Validated against the device rather than against the register. An EEPROM auto-increments its pointer after a read, so priming the pointer and repeating the read with the bit set has a predicted answer: the next byte, not the one named. Eight consecutive reads returned SPD bytes 0x01 through 0x08 in order, matching an ordinary dump. Send Byte was confirmed on the DDR4 page-select addresses, which hold a latch and store no data, so the page state is itself the readout. Result: ee1004 binds on all four SPD addresses and decode-dimms decodes all four modules with both CRCs valid on each. The part number comes off page 1, so the page select runs end to end. The four module serial numbers are unchanged from the baseline recorded before this series. SMBus Quick stays unimplemented. Beyond having no obvious encoding, a write into the 0x30-0x37 range is how an EE1004 SPD is write-protected, permanently on many modules, so an adapter on the memory bus should not advertise a probe that writes. i2cdetect scans in read mode. Also fix test-smoke.sh resolving the module through modinfo, which silently tested the installed DKMS build instead of the one just compiled. It now prefers the local .ko and prints which it loaded. Smoke suite: 19 passed, 0 failed. checkpatch --strict 0/0/0, in-tree W=1 and Sparse clean. |
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|
Simone
|
88a8b7eb27 |
i2c-imc-skylake: retract the CF8/CFC claim, harden the state machine
v2 said firmware filters CF8/CFC config writes to this function and that
the registers are reachable only through ECAM. That was never tested; the
only evidence was the boot line "PCI: Using configuration type 1", which
names the accessor and says nothing about a write failing.
Measured on the board, driver unloaded:
# setpci -s 16:1e.5 9c.L=20085002 # read SPD 0x50 register 0x02
# setpci -s 16:1e.5 9c.L
20005002 # GO consumed by the engine
# setpci -s 16:1e.5 a8.L
0000500c # READ_DONE, no error
# setpci -s 16:1e.5 b4.L
0000000c # SPD byte 2, DDR4 type code
The command executes and returns correct data through the ordinary
accessors, and MSR_SMI_COUNT does not move across it. So the driver now
uses pci_read_config_dword() and pci_write_config_dword(), the submission
is a single patch again, and nothing in it touches the PCI core. The
cover letter retracts the claim explicitly rather than dropping it
quietly, because v2 was posted with it.
Correctness work in the same pass:
- the completion bits are latched, so a command word that never reaches
the register is indistinguishable from a completed transfer and the
caller gets the previous transaction's data. Read the command word
back and require it to be the one just written; the engine only ever
clears GO, which the measurement above shows directly;
- compare the command registers after every transfer against what the
driver left in them and fail with -EAGAIN on a mismatch. The original
iMC driver had this check and it is what makes an unarbitrated system
detectable instead of silently wrong;
- use the i2c core's suspended-adapter mechanism rather than a private
flag and -EHOSTDOWN;
- use devm_mutex_init(), drop the unnecessary pci_enable_device(), and
return -ENODEV rather than -EPERM from the default-off gate, which was
printing a driver-core error on every boot;
- mask GO when restoring a saved command word.
An earlier version of the latched-DONE check required the GO bit to be
seen set or the status word to change. That was wrong: repeated transfers
with the same outcome leave STATUS bit for bit identical, and GO is
consumed faster than a config read-back can observe it. It produced false
positives on 3 of 15 smoke-test items before being replaced.
Add Documentation/i2c/busses/i2c-imc-skylake.rst, which every other PC
SMBus driver has and which was asked for on the 2020 iMC thread, and the
tools/ scripts for the hardware measurements: probe-cf8-write.sh and
probe-cf8-transaction.sh produced the result above, dump-pcu-config.sh is
the search for a TSOD polling control, watch-engine.sh is the firmware
activity measurement.
Smoke test on the X299 system with the current module: 15 checks, 0
failures, dmesg clean.
|
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Simone
|
3cd1d6e0a6 |
i2c-imc-skylake: split the submission into a PCI patch and the driver
The driver reached the PCU function's config space by walking the ACPI MCFG
table and mapping the ECAM page itself. That is one leaf driver deciding
config-space policy, and no other driver in mainline does it, so it was the
single most likely reason for a NAK.
Move that decision where it belongs: the upstream series is now two patches,
a PCI/x86 accessor that forces the memory-mapped path with the core's
locking, and this driver on top of it. Reviewers on each side now get
something they can act on, and get_maintainer.pl selects the PCI and x86
people by itself.
Correctness work in the same pass:
- the completion bits are latched, so a command the engine never accepted
was indistinguishable from a completed one and returned the previous
transaction's data as valid. Require a positive sign that the engine
acted on the command;
- compare the command registers after every transfer against what the
driver left in them and fail with -EAGAIN on a mismatch. The original
iMC driver had this check and it is what makes an unarbitrated system
detectable instead of silently wrong;
- use the i2c core's suspended-adapter mechanism rather than a private
flag and -EHOSTDOWN;
- use devm_mutex_init(), drop the unnecessary pci_enable_device(), and
return -ENODEV rather than -EPERM from the default-off gate, which was
printing a driver-core error on every boot;
- mask GO when restoring a saved command word.
Stop attributing the dropped CF8/CFC write to System Management Mode. The
only evidence was a boot log line naming the access method, which says
nothing about who filters the write. tools/probe-cf8-write.sh is there to
settle it with an MSR_SMI_COUNT measurement.
Add Documentation/i2c/busses/i2c-imc-skylake.rst, which every other PC SMBus
driver has and which was explicitly asked for on the 2020 iMC thread, the
tools/ scripts for the hardware measurements the submission still owes, and
compat/pci-mmcfg-compat.h so the driver still builds out-of-tree against a
kernel without the new accessor while the source stays byte-identical to the
submitted patch.
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Simone
|
3c86f6c866 |
docs: correct i2cdetect usage and ignore archived notes
The engine exposes only SMBus BYTE_DATA/WORD_DATA, so i2cdetect (which needs SMBus QUICK or READ_BYTE) cannot scan the bus. Replace the misleading "i2cdetect -r/-y" scan instructions with a direct i2cget byte-data read in the README, the cover letter and the smoke test. Also gitignore the archived internal working documents (docs/archive-*.md). Signed-off-by: Simone Chifari <[email protected]> |
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Simone
|
4697ce3e3b |
i2c: imc-skylake: add driver for Intel Skylake-X iMC SMBus engine
Add a driver for the integrated memory controller (iMC) SMBus engine on Intel Skylake-X / Cascade Lake-X processors (socket LGA 2066, platform X299, PCU function 8086:2085). The engine provides two SMBus channels — one per pair of DIMM slots — over which SPD EEPROMs, DDR4 thermal sensors and third-party LED controllers are accessible. Exposing it as a pair of standard Linux I2C adapters lets existing tools (i2c-tools, lm-sensors) use it without bespoke sysfs hacks. Key design decisions: - ECAM MMIO access instead of CF8/CFC port I/O (SMM traps port writes) - Dynamic MCFG table parsing for mmcfg_base (no hardcoding) - Support for SMBus BYTE_DATA and WORD_DATA transfers - devm-managed resources with automatic cleanup - Global mutex to serialize transactions across both channels sharing the same ECAM mapping Signed-off-by: Simone Chifari <[email protected]> |