Re: msm8909 support in a recent kernel

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 07 Dec 06:13 PST 2017, Will Newton wrote:
[..]
> 
> I think I have narrowed down the issue to the fact that the qcom_smd
> driver is not getting any interrupts. I get a channel created:
> 
> [    0.728352]  smd:rpm: new channel 'rpm_requests' info-size: 88
> fifo-size: 1024
> [    0.731684]  smd:rpm: new channel found: 'rpm_requests'
> 

That's good.

> But on the first (and only) time through qcom_channel_state_worker the
> channel is in state FLUSHING so we never create a device. Any idea why
> I might not be getting any interrupts?
> 

I presume you mean the value of GET_RX_CHANNEL_INFO(channel, state)
here. This has been reported on 8994 as well and do stem from a
misunderstanding of mine when it comes to how the state machine is
ticking when a channel is closed.

What we see on 8994 is that the boot loader opens the rpm_requests
channel, send a few regulator requests and then put the channel (the
apps side of it) in closing state. During boot of the Linux kernel the
rpm_requests channel is then found in "closing" state.

And looking at LK, the two platforms implementing this schema are 8994
and 8909.


My two hypothesises for 8994 was that we could either:

1) Complete the closing (i.e. not leave the channel in closing/reset
state) and that might cause the other side to move to "opening" again,
or
2) take a more active role in driving the channel to opening,
based on the knowledge that Linux do have someone to interested in
communicating over this link.

The first is pretty close of being a hack and the second relies on this
loop figuring out if there is going to be a driver-device match in the
future.

Unfortunately, this being reported on 8994 gave it a low priority, so
it's been sitting far down on my todo list ever since.

> The irq numbers etc. all look correct as far as I can tell. smem and
> tcsr-mutex also look OK. I'm not sure about apcs as I don't have clear
> documentation on what it actually entails e.g. I have SAW devices
> setup which seem to be part of APCS but not sure what else.

Looked at the documentation, apcs should be defined as reg = <0x0b011000
0x1000> and qcom,ipc should be <&apcs 8 0>. I.e. exactly the same as
8916.

Regards,
Bjorn