Add documentation for the DRM_WEDGE_RECOVERY_COLD_RESET recovery method. This method is designated for severe error conditions that compromise core device functionality and are unrecoverable via other recovery methods such as driver rebind or bus reset. The documentation clarifies when this recovery method should be used and its implications for userspace.
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. Signed-off-by: Mallesh Koujalagi <[email protected]> --- Documentation/gpu/drm-uapi.rst | 60 +++++++++++++++++++++++++++++++++- 1 file changed, 59 insertions(+), 1 deletion(-) diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 579e87cb9ff7..d8b3608c5cbb 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -418,7 +418,7 @@ 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`_ @@ -435,6 +435,7 @@ following expectations. rebind unbind + bind driver bus-reset unbind + bus reset/re-enumeration + bind vendor-specific vendor specific recovery method + cold-reset full device cold reset required unknown consumer policy =============== ======================================== @@ -447,6 +448,14 @@ 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 cold reset to restore +functionality. + Vendor Specific Recovery ------------------------ @@ -524,6 +533,55 @@ 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: $DEVICE" + + # Try slot power reset first + SLOT=$(find /sys/bus/pci/slots/ -type l 2>/dev/null | while read slot; do + ADDR=$(cat "$slot" 2>/dev/null) + [ -n "$ADDR" ] && echo "$DEVICE" | grep -q "^$ADDR" && basename $(dirname "$slot") && break + done) + + if [ -n "$SLOT" ]; then + echo "Using slot $SLOT" + + # Unbind driver + [ -e "/sys/bus/pci/devices/$DEVICE/driver" ] && \ + echo "$DEVICE" > /sys/bus/pci/devices/$DEVICE/driver/unbind 2>/dev/null + + # 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
