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--- en:pcie:hot-reset-linux [2019/04/16 21:01] – alex
+++ en:pcie:hot-reset-linux [2020/04/29 05:59] (current) – alex
@@ Line 3: / Line 3: @@
 Resets in PCI express are a bit complex. There are two main types of resets - conventional reset, and function-level reset. There are also two types of conventional resets, fundamental resets and non-fundamental resets. See the PCI express specification for all of the details.
-A 'cold reset' is a fundamental reset that takes place after power is applied to a PCIe device. There appears to be no standard way of triggering a cold reset, save for turning the system off and back on again. On my machines, the /sys/bus/pci/slots directory is empty.
+A 'cold reset' is a fundamental reset that takes place after power is applied to a PCIe device. There appears to be no standard way of triggering a cold reset, save for turning the system off and back on again. On my machines, the ''/sys/bus/pci/slots'' directory is empty.
 A 'warm reset' is a fundamental reset that is triggered without disconnecting power from the device. There appears to be no standard way of triggering a warm reset.
@@ Line 11: / Line 11: @@
 A 'function-level reset' (FLR) is a reset that affects only a single function of a PCI express device. It must not reset the entire PCIe device. Implementing function-level resets is not required by the PCIe specification. A function-level reset is initiated by setting the initiate function-level reset bit in the function's device control register in the PCI express capability structure in the PCI configuration space.
-Linux exposes the function-level reset functionality in the form of /sys/bus/pci/devices/$dev/reset. Writing a 1 to this file will initiate a function-level reset on the corresponding function. Note that this only affects that specific function of the device, not the whole device, and devices are not required to implement function-level resets as per the PCIe specification.
+Linux exposes the function-level reset functionality in the form of ''/sys/bus/pci/devices/$dev/reset''. Writing a 1 to this file will initiate a function-level reset on the corresponding function. Note that this only affects that specific function of the device, not the whole device, and devices are not required to implement function-level resets as per the PCIe specification.
 I am not aware of any 'nice' method for triggering a hot reset (there is no sysfs entry for that). However, it is possible to use setpci to do so with the following script:
-<code sh>
+<code bash pcie_hot_reset.sh>
 #!/bin/bash
@@ Line 25: / Line 25: @@
     exit 1
 fi
+if [ ! -e "/sys/bus/pci/devices/$dev" ]; then
+    dev="0000:$dev"
+fi
+if [ ! -e "/sys/bus/pci/devices/$dev" ]; then
+    echo "Error: device $dev not found"
+    exit 1
+fi
+port=$(basename $(dirname $(readlink "/sys/bus/pci/devices/$dev")))
+if [ ! -e "/sys/bus/pci/devices/$port" ]; then
+    echo "Error: device $port not found"
+    exit 1
+fi
+echo "Removing $dev..."
+echo 1 > "/sys/bus/pci/devices/$dev/remove"
+echo "Performing hot reset of port $port..."
+bc=$(setpci -s $port BRIDGE_CONTROL)
+echo "Bridge control:" $bc
+setpci -s $port BRIDGE_CONTROL=$(printf "%04x" $(("0x$bc" | 0x40)))
+sleep 0.01
+setpci -s $port BRIDGE_CONTROL=$bc
+sleep 0.5
+echo "Rescanning bus..."
+echo 1 > "/sys/bus/pci/devices/$port/rescan"
 </code>
@@ Line 30: / Line 65: @@
 Ensure that all attached drivers are unloaded before running this script. This script will attempt to remove the PCIe device, then command the upstream switch port to issue a hot reset, then attempt to rescan the PCIe bus. This script has also only been tested on devices with a single function, so it may need some reworking for devices with multiple functions.
+[[https://unix.stackexchange.com/a/474378/55879|Answer on Stack Exchange]]