Re: msm8909 support in a recent kernel

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On Thu, Dec 7, 2017 at 2:13 PM, Will Newton <will.newton@xxxxxxxxx> wrote:
> On Wed, Dec 6, 2017 at 9:58 PM, Bjorn Andersson
> <bjorn.andersson@xxxxxxxxxx> wrote:
>
> Hi Bjorn,
>
>>> On Wed, Dec 6, 2017 at 6:43 PM, Bjorn Andersson
>>> <bjorn.andersson@xxxxxxxxxx> wrote:
>>> > On Wed 06 Dec 06:39 PST 2017, Will Newton wrote:
>>> >
>>> >> On Wed, Dec 6, 2017 at 2:45 AM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
>>> >> > On 12/01, Will Newton wrote:
>>> >> >> On Wed, Nov 29, 2017 at 6:50 PM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
>>> >> >>
>>> >> >> > It's not completely insane to support this SoC upstream though. You'd
>>> >> >> > have to bring in the pinctrl and clk drivers, which may be a bit of
>>> >> >> > effort. After that it should mostly be enabling various devices by
>>> >> >> > adding DT nodes and testing things out. It looks like this is 32-bit, so
>>> >> >> > getting SMP support may require some tweaks to the smp_ops code for qcom
>>> >> >> > platforms. You're right that it isn't too different from msm8916, so it
>>> >> >> > may be that most of the driver support for that SoC transfers over
>>> >> >> > nicely to this one.
>>> >> >>
>>> >> >> I've started from the 8916 drivers and started to port in the changes
>>> >> >> from the 3.18 tree that seem relevant. I have a kernel that boots and
>>> >> >> talks over the serial. I've done a bunch of pinctrl although it is not
>>> >> >> complete yet. I've had a look at the clocks and got the PLL working
>>> >> >> but I think I'm probably missing a document that describes the
>>> >> >> clocking architecture in more detail (I have the register reference
>>> >> >> but that's a bit of a worm's eye view).
>>> >> >>
>>> >> >> The current issue I am experiencing is the first write to an SPMI
>>> >> >> channel causes the board to reset. I suspect this means that I have
>>> >> >> not setup clocks correctly somewhere?
>>> >> >
>>> >> > The SPMI controller typically always has clks enabled, so I would
>>> >> > be surprised if the clk was off. More likely, you're attempting
>>> >> > to read/write a channel that is locked down and triggering an
>>> >> > access control violation. Something configured incorrectly in DT
>>> >> > perhaps?
>>> >>
>>> >> The DT is certainly the most likely place to find the problem, the
>>> >> SPMI driver etc. are mostly the same as 3.18.
>>> >>
>>> >> The problem I am seeing is when the registers are initialized for the
>>> >> s2 regulator (via SPMI), which I think is powering the CPU core (I
>>> >> don't have the pm8909 docs sadly, only pm8916) and even though no bits
>>> >> in the register get changed as part of the init, the writeback of the
>>> >> register causes the board to reset.
>>> >>
>>> >> In general I am having a bit if trouble understanding the regulator
>>> >> setup. It seems like there are the RPM regulators - these don't seem
>>> >> to be detected correctly. I get a remote_state of FLUSHING in
>>> >> qcom_channel_state_worker which stops the devices being setup.
>>> >>
>>> >
>>> > Many regulators in the system feeds multiple subsystems, e.g. apps,
>>> > modem, wireless. To support this there is a separate co-processor - the
>>> > RPM - that take requests from all subsystems and then control the PMIC.
>>> > For these regulators the PMIC registers are locked down and accessing
>>> > these would typically cause a system reset.
>>> >
>>> > To communicate with the RPM you would need to enable tcsr-mutex, smem,
>>> > apcs and smd/rpm/rpm_request like done for 8916. It's probable that the
>>> > only code you need to write is in qcom_smd-regulator.c to add the list
>>> > of regulators and their parameters.
>>>
>>> Thanks, that's really helpful, I'll make sure I have all those functioning.
>>>
>>> It does look like for the 8916 the same list of regulators (s1-s4,
>>> l1-l18) is listed in both the spmi_bus section and the rpm_bus section
>>> of the dts. What is it that decides whether a regulator is part of the
>>> RPM set or the SPMI set - is it a property of the SoC that can be read
>>> somewhere?
>>
>> I don't believe this is documented anywhere, except that by looking at
>> the downstream DTS, where you should be able to see which ones are
>> active and actually are referenced by clients.
>>
>> But as I said, you can start off by only addressing the regulators
>> through the RPM, that should help you reach a functional state.
>
> 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'
>
> 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?
>
> 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.

Is there any potential for version skew here between the RPM processor
and Linux? I have an rpm.mbn binary but I have no idea what is in it,
I just know it works with 3.18.
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