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| 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. | 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. | 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. | ||
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| 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. | 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: | 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 bash pcie_hot_reset.sh> | |
| - | + | ||
| - | <code sh> | + | |
| #!/bin/bash | #!/bin/bash | ||
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| 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. | 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]] | ||