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The MHI bus supports a standardized hardware reset, which is known as the "SoC Reset". This reset is similar to the reset sysfs for PCI devices - a hardware mechanism to reset the state back to square one. The MHI SoC Reset is described in the spec as a reset of last resort. If some unrecoverable error has occurred where other resets have failed, SoC Reset is the "big hammer" that ungracefully resets the device. This is effectivly the same as yanking the power on the device, and reapplying it. However, depending on the nature of the particular issue, the underlying transport link may remain active and configured. If the link remains up, the device will flag a MHI system error early in the boot process after the reset is executed, which allows the MHI bus to process a fatal error event, and clean up appropiately. While the SoC Reset is generally intended as a means of recovery when all else has failed, it can be useful in non-error scenarios. For example, if the device loads firmware from the host filesystem, the device may need to be fully rebooted inorder to pick up the new firmware. In this scenario, the system administrator may use the soc_reset sysfs to cause the device to pick up the new firmware that the admin placed on the filesystem. Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com> Reviewed-by: Bhaumik Bhatt <quic_bbhatt@quicinc.com> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Link: https://lore.kernel.org/r/1650302327-30439-1-git-send-email-quic_jhugo@quicinc.com Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
31 lines
1.4 KiB
Text
31 lines
1.4 KiB
Text
What: /sys/bus/mhi/devices/.../serialnumber
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Date: Sept 2020
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KernelVersion: 5.10
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Contact: Bhaumik Bhatt <bbhatt@codeaurora.org>
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Description: The file holds the serial number of the client device obtained
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using a BHI (Boot Host Interface) register read after at least
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one attempt to power up the device has been done. If read
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without having the device power on at least once, the file will
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read all 0's.
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Users: Any userspace application or clients interested in device info.
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What: /sys/bus/mhi/devices/.../oem_pk_hash
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Date: Sept 2020
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KernelVersion: 5.10
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Contact: Bhaumik Bhatt <bbhatt@codeaurora.org>
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Description: The file holds the OEM PK Hash value of the endpoint device
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obtained using a BHI (Boot Host Interface) register read after
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at least one attempt to power up the device has been done. If
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read without having the device power on at least once, the file
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will read all 0's.
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Users: Any userspace application or clients interested in device info.
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What: /sys/bus/mhi/devices/.../soc_reset
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Date: April 2022
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KernelVersion: 5.19
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Contact: mhi@lists.linux.dev
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Description: Initiates a SoC reset on the MHI controller. A SoC reset is
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a reset of last resort, and will require a complete re-init.
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This can be useful as a method of recovery if the device is
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non-responsive, or as a means of loading new firmware as a
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system administration task.
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