Simone
3cd1d6e0a6
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.
129 lines
3.8 KiB
Bash
Executable File
129 lines
3.8 KiB
Bash
Executable File
#!/usr/bin/env bash
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#
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# WRITES TO HARDWARE. Answers two questions the submission still owes:
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#
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# 1. does a CF8/CFC dword write to the iMC SMBus command register take
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# effect on this board?
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# 2. does that write raise an SMI?
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#
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# It modifies only the register/offset field, DATA[7:0], while the GO bit is
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# clear, so no SMBus transaction is issued, and it restores the original value
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# on every exit path. It refuses to run if the engine is busy, if a transaction
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# is armed, if TSOD is active, or if the driver is loaded.
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#
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set -euo pipefail
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# shellcheck source=tools/common.sh
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source "$(dirname "$(readlink -f "$0")")/common.sh"
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GO_BIT=$((1 << 19))
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TSOD_ACTIVE_BIT=$((1 << 20))
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STAT_BUSY=1
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CHANNEL=0
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CONFIRMED=false
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while (($#)); do
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case $1 in
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--i-understand) CONFIRMED=true; shift ;;
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--channel) CHANNEL=$2; shift 2 ;;
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-h|--help)
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sed -n '3,14p' "$0"
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echo "usage: $0 --i-understand [--channel 0|1]"
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exit 0
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;;
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*) die "unknown argument: $1" ;;
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esac
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done
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if ! $CONFIRMED; then
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cat >&2 <<-'EOF'
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This script writes to a register of the memory controller's SMBus engine.
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It is written to be a no-op for the bus: the GO bit stays clear, so no
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SMBus transaction is issued, and the original register value is restored
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before the script exits. It is still a write to firmware-owned hardware.
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Re-run with --i-understand to proceed.
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EOF
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exit 2
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fi
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require_root
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require_cmd lspci setpci awk
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case $CHANNEL in
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0) REG_DATA=$REG_CH0_DATA; REG_STAT=$REG_CH0_STAT ;;
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1) REG_DATA=$REG_CH1_DATA; REG_STAT=$REG_CH1_STAT ;;
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*) die "channel must be 0 or 1" ;;
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esac
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if ! command -v rdmsr >/dev/null; then
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echo "warning: rdmsr not found, the SMI question will stay unanswered." >&2
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echo " install msr-tools and 'modprobe msr' for the full result." >&2
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fi
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driver_is_loaded && die "unload i2c-imc-skylake first"
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BDF=$(find_pcu)
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echo "device: $BDF"
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echo "channel: $CHANNEL (DATA at $REG_DATA, STATUS at $REG_STAT)"
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echo
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original=$(read_reg "$BDF" "$REG_DATA")
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status=$(read_reg "$BDF" "$REG_STAT")
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echo "DATA before: $original"
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echo "STATUS before: $status"
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((original & GO_BIT)) && die "GO is set: a transaction is armed, refusing"
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((original & TSOD_ACTIVE_BIT)) &&
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die "TSOD_ACTIVE is set: firmware is using the engine, refusing"
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((status & STAT_BUSY)) && die "engine is BUSY, refusing"
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restore()
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{
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setpci -s "$BDF" "$REG_DATA.L=$(printf '%08x' "$original")" || true
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echo "DATA restored to $(read_reg "$BDF" "$REG_DATA")"
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}
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trap restore EXIT
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# Flip the low byte to something that is certainly different, GO still clear.
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probe=$(( (original & ~0xff) | ( ((original & 0xff) ^ 0x5a) & 0xff ) ))
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probe_hex=$(printf '0x%08x' "$probe")
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smi_before=$(read_smi_count)
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echo
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echo "writing $probe_hex through CF8/CFC (setpci)..."
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setpci -s "$BDF" "$REG_DATA.L=$(printf '%08x' "$probe")"
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readback=$(read_reg "$BDF" "$REG_DATA")
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smi_after=$(read_smi_count)
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echo "DATA after write: $readback"
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echo
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echo "=== result 1: did the write take effect? ==="
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if [[ "$readback" == "$probe_hex" ]]; then
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echo "STUCK - the CF8/CFC write reached the register."
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echo " The premise of the ECAM patch does not hold on this board;"
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echo " do not claim CF8/CFC writes are dropped."
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else
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echo "DROPPED - wrote $probe_hex, read back $readback."
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echo " Confirms that CF8/CFC writes to this function do not"
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echo " take effect on this board."
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fi
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echo
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echo "=== result 2: was an SMI raised? ==="
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if ((smi_before < 0 || smi_after < 0)); then
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echo "UNKNOWN - MSR_SMI_COUNT not readable (need msr-tools + modprobe msr)."
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else
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delta=$((smi_after - smi_before))
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echo "MSR_SMI_COUNT: $smi_before -> $smi_after (delta $delta)"
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if ((delta == 0)); then
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echo "NO SMI - the behaviour must not be attributed to SMM."
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else
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echo "SMI RAISED - System Management Mode is involved; say so, with"
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echo " this number, in the changelog."
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fi
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fi
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