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

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Message-ID: <90c0a654-a02f-46e2-96a9-34f6a30c95a0@quicinc.com>
Date: Tue, 9 Jan 2024 17:20:37 +0800
From: Qiang Yu <quic_qianyu@...cinc.com>
To: Manivannan Sadhasivam <mani@...nel.org>,
        Jeffrey Hugo
	<quic_jhugo@...cinc.com>
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 1/3/2024 12:52 AM, Manivannan Sadhasivam wrote:
> On Tue, Jan 02, 2024 at 08:31:15AM -0700, Jeffrey Hugo wrote:
>> 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?
>>
> All points raised by Jeff are valid. I had discussions with Hemant and Bhaumik
> previously on allowing the devices to enter EDL mode in a generic manner and we
> didn't conclude on one final approach.
>
> Whatever way we come up with, it should be properly described in the MHI spec
> and _should_ be backwards compatible.

Hi Mani, Jeff. The method of entering EDL mode is documented in MHI spec 
v1.2, Chapter 13.2.

Could you please check once?

>
> - Mani
>
>> -Jeff