On 1/9/2024 2:20 AM, Qiang Yu wrote:
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@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?
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?
I do see it listed there. However that was a FR for SDX55, so devices
prior to that would not support this. AIC100 predates this change and
would not support the functionality. I verified the AIC100
implementation is not aware of this cookie.
Also, that functionality depends on channel 91 being reserved per the
table 9-2, however that table only applies to modem class devices as it
is under chapter 9 "Modem protocols over PCIe". Looking at the ath11k
and ath12k implementations in upstream, it looks like they partially
comply. Other devices have different MHI channel definitions.
Chapter 9 doesn't appear to be in older versions of the spec that I
have, so it is unclear if this functionality is backwards compatible
(was channel 91 used for another purpose in pre-SDX55 modems).
I'm not convinced this belongs in the MHI core. At a minimum, the MHI
controller(s) for the applicable devices needs to opt-in to this.
-Jeff
