When ``WEDGED=cold-reset`` is sent, it indicates that the device has encountered an error condition that cannot be resolved through other recovery methods such as driver rebind or bus reset, and requires a complete device power cycle to restore functionality.
Signed-off-by: Mallesh Koujalagi <[email protected]> --- v2: - Add several instead of number to avoid update. (Jani) v3: - Update document with generic scenario. (Riana) - Consistent with terminology. (Raag) - Remove already covered information. v4: - Update doc. (Raag/Riana) - Change commit message. v5: - Update commit message. (Raag) - Remove unbind. - Simplify cold-reset script. --- Documentation/gpu/drm-uapi.rst | 64 +++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 32206ce62931..809386f16521 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -422,7 +422,7 @@ needed. Recovery -------- -Current implementation defines four recovery methods, out of which, drivers +Current implementation defines several recovery methods, out of which, drivers can use any one, multiple or none. Method(s) of choice will be sent in the uevent environment as ``WEDGED=<method1>[,..,<methodN>]`` in order of less to more side-effects. See the section `Vendor Specific Recovery`_ @@ -439,6 +439,7 @@ following expectations. rebind unbind + bind driver bus-reset unbind + bus reset/re-enumeration + bind vendor-specific vendor specific recovery method + cold-reset remove device + slot power cycle + rescan unknown consumer policy =============== ======================================== @@ -451,6 +452,17 @@ debug purpose in order to root cause the hang. This is useful because the first hang is usually the most critical one which can result in consequential hangs or complete wedging. +Cold Reset Recovery +------------------- + +When ``WEDGED=cold-reset`` is sent, it indicates that the device has +encountered an error condition that cannot be resolved through other +recovery methods such as driver rebind or bus reset, and requires a complete +device power cycle to restore functionality. + +This method is used by devices that are plugged directly into the PCIe slot +which supports removing the power. + Vendor Specific Recovery ------------------------ @@ -528,6 +540,56 @@ Recovery script:: echo -n $DEVICE > $DRIVER/unbind echo -n $DEVICE > $DRIVER/bind +Example - cold-reset +-------------------- + +Udev rule:: + + SUBSYSTEM=="drm", ENV{WEDGED}=="cold-reset", DEVPATH=="*/drm/card[0-9]", + RUN+="/path/to/cold-reset.sh $env{DEVPATH}" + +Recovery script:: + + #!/bin/sh + + [ -z "$1" ] && echo "Usage: $0 <device-path>" && exit 1 + + # Get device + DEVPATH=$(readlink -f /sys/$1/device 2>/dev/null || readlink -f /sys/$1) + DEVICE=$(basename $DEVPATH) + + echo "Cold reset: $DEVICE" + + # Try slot power reset first + SLOT="" + for addr_file in /sys/bus/pci/slots/*/address; do + [ -f "$addr_file" ] || break + addr=$(cat "$addr_file" 2>/dev/null) + [ -n "$addr" ] || continue + case "$DEVICE" in + "$addr"*) SLOT=$(basename "$(dirname "$addr_file")"); break ;; + esac + done + + if [ -n "$SLOT" ]; then + echo "Using slot $SLOT" + + # Remove device + echo 1 > /sys/bus/pci/devices/$DEVICE/remove + + # Power cycle slot + echo 0 > /sys/bus/pci/slots/$SLOT/power + sleep 2 + echo 1 > /sys/bus/pci/slots/$SLOT/power + sleep 1 + + # Rescan + echo 1 > /sys/bus/pci/rescan + echo "Done!" + else + echo "No slot found" + fi + Customization ------------- -- 2.34.1
