Re: [PATCH] bus: mhi: host: Add sysfs entry to force device to enter EDL

[Qiang Yu]

On 1/2/2024 11:31 PM, Jeffrey Hugo wrote:
> On 12/25/2023 12:47 AM, Qiang Yu wrote:
> > From: Bhaumik Bhatt <quic_bbhatt@xxxxxxxxxxx>
> >
> > Forcing the device (eg. SDX75) to enter Emergency Download Mode involves
> > writing the 0xEDEDEDED cookie to the channel 91 doorbell register and
> > forcing an SOC reset afterwards. Allow users of the MHI bus to 
> > exercise the
> > sequence using a sysfs entry.
>
> I don't see this documented in the spec anywhere.  Is this standard 
> behavior for all MHI devices?

This is documented in MHI spec v1.2, 13.2 Emergency download (EDL) mode 
cookie. So I think

it is standard behavior. At least, SDX65 and SDX75 support it.

> What about devices that don't support EDL mode?
>
> How should the host avoid using this special cookie when EDL mode is 
> not desired?

Can I include another flag in mhi_pci_dev_info and mhi_controller and 
check this flag

before writing EDL cookie?

> -Jeff