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xhci DbC driver polls the host controller for DbC events at a reduced rate when DbC is enabled but there are no active data transfers. Allow users to modify this reduced poll interval via dbc_poll_interval_ms sysfs entry. Unit is milliseconds and accepted range is 0 to 5000. Max interval of 5000 ms is selected as it matches the common 5 second timeout used in usb stack. Default value is 64 milliseconds. A long interval is useful when users know there won't be any activity on systems connected via DbC for long periods, and want to avoid battery drainage due to unnecessary CPU usage. Example being Android Debugger (ADB) usage over DbC on ChromeOS systems running Android Runtime. [minor changes and rewording -Mathias] Co-developed-by: Samuel Jacob <samjaco@google.com> Signed-off-by: Samuel Jacob <samjaco@google.com> Signed-off-by: Uday M Bhat <uday.m.bhat@intel.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Link: https://lore.kernel.org/r/20240626124835.1023046-5-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
87 lines
3.5 KiB
Text
87 lines
3.5 KiB
Text
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc
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Date: June 2017
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Contact: Lu Baolu <baolu.lu@linux.intel.com>
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Description:
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xHCI compatible USB host controllers (i.e. super-speed
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USB3 controllers) are often implemented with the Debug
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Capability (DbC). It can present a debug device which
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is fully compliant with the USB framework and provides
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the equivalent of a very high performance full-duplex
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serial link for debug purpose.
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The DbC debug device shares a root port with xHCI host.
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When the DbC is enabled, the root port will be assigned
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to the Debug Capability. Otherwise, it will be assigned
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to xHCI.
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Writing "enable" to this attribute will enable the DbC
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functionality and the shared root port will be assigned
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to the DbC device. Writing "disable" to this attribute
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will disable the DbC functionality and the shared root
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port will roll back to the xHCI.
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Reading this attribute gives the state of the DbC. It
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can be one of the following states: disabled, enabled,
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initialized, connected, configured and stalled.
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What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idVendor
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Date: March 2023
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Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
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Description:
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This dbc_idVendor attribute lets us change the idVendor field
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presented in the USB device descriptor by this xhci debug
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device.
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Value can only be changed while debug capability (DbC) is in
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disabled state to prevent USB device descriptor change while
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connected to a USB host.
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The default value is 0x1d6b (Linux Foundation).
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It can be any 16-bit integer.
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What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idProduct
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Date: March 2023
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Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
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Description:
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This dbc_idProduct attribute lets us change the idProduct field
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presented in the USB device descriptor by this xhci debug
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device.
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Value can only be changed while debug capability (DbC) is in
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disabled state to prevent USB device descriptor change while
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connected to a USB host.
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The default value is 0x0010. It can be any 16-bit integer.
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What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bcdDevice
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Date: March 2023
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Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
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Description:
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This dbc_bcdDevice attribute lets us change the bcdDevice field
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presented in the USB device descriptor by this xhci debug
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device.
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Value can only be changed while debug capability (DbC) is in
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disabled state to prevent USB device descriptor change while
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connected to a USB host.
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The default value is 0x0010. (device rev 0.10)
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It can be any 16-bit integer.
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What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bInterfaceProtocol
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Date: March 2023
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Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
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Description:
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This attribute lets us change the bInterfaceProtocol field
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presented in the USB Interface descriptor by the xhci debug
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device.
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Value can only be changed while debug capability (DbC) is in
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disabled state to prevent USB descriptor change while
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connected to a USB host.
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The default value is 1 (GNU Remote Debug command).
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Other permissible value is 0 which is for vendor defined debug
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target.
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What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_poll_interval_ms
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Date: February 2024
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Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
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Description:
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This attribute adjust the polling interval used to check for
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DbC events. Unit is milliseconds. Accepted values range from 0
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up to 5000. The default value is 64 ms.
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This polling interval is used while DbC is enabled but has no
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active data transfers.
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