docs: ABI: sysfs-bus-mhi: Update contact info

@codeaurora.org email addresses are no longer valid and will bounce to
sender. Also, Bhaumik has previously indicated he is no longer interested
in participating in MHI bus discussions.

Update contact info from Bhaumik to the mhi mail list so that mails will
be routed to the MHI maintainers and interested parties.

Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://lore.kernel.org/r/20230628182346.3855-1-quic_jhugo@quicinc.com
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

bus: mhi: host: Add soc_reset sysfs

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>

bus: mhi: core: Introduce sysfs entries for MHI

Introduce sysfs entries to enable userspace clients the ability to read
the serial number and the OEM PK Hash values obtained from BHI. OEMs
need to read these device-specific hardware information values through
userspace for factory testing purposes and cannot be exposed via degbufs
as it may remain disabled for performance reasons. Also, update the
documentation for ABI to include these entries.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
[mani: used dev_groups to manage sysfs attributes]
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200929175218.8178-16-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>