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

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Message-ID: <cff4b828-9566-a2bd-287a-138d74a76a59@quicinc.com>
Date: Tue, 2 Jan 2024 08:31:15 -0700
From: Jeffrey Hugo <quic_jhugo@...cinc.com>
To: Qiang Yu <quic_qianyu@...cinc.com>, <mani@...nel.org>
CC: <mhi@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_cang@...cinc.com>,
        <quic_mrana@...cinc.com>, Bhaumik Bhatt <quic_bbhatt@...cinc.com>
Subject: Re: [PATCH] bus: mhi: host: Add sysfs entry to force device to enter
 EDL

On 12/25/2023 12:47 AM, Qiang Yu wrote:
> From: Bhaumik Bhatt <quic_bbhatt@...cinc.com>
> 
> 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?

What about devices that don't support EDL mode?

How should the host avoid using this special cookie when EDL mode is not 
desired?

-Jeff