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Subject: Re: [RESEND PATCH v1 0/5] Solve postboot supplier cleanup and
 optimize probe ordering
To:     Sandeep Patil <sspatil@android.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Saravana Kannan <saravanak@google.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        David Collins <collinsd@codeaurora.org>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com
References: <20190604003218.241354-1-saravanak@google.com>
 <20190624223707.GH203031@google.com> <20190625035313.GA13239@kroah.com>
 <20190626043052.GF212690@google.com>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <f9ddae55-91b3-27b2-0919-579f4d895e99@gmail.com>
Date:   Tue, 25 Jun 2019 22:49:32 -0700
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On 6/25/19 9:30 PM, Sandeep Patil wrote:
> On Tue, Jun 25, 2019 at 11:53:13AM +0800, Greg Kroah-Hartman wrote:
>> On Mon, Jun 24, 2019 at 03:37:07PM -0700, Sandeep Patil wrote:
>>> We are trying to make sure that all (most) drivers in an Aarch64 system can
>>> be kernel modules for Android, like any other desktop system for
>>> example. There are a number of problems we need to fix before that happens
>>> ofcourse.
>>
>> I will argue that this is NOT an android-specific issue.  If the goal of
>> creating an arm64 kernel that will "just work" for a wide range of
>> hardware configurations without rebuilding is going to happen, we need
>> to solve this problem with DT.  This goal was one of the original wishes
>> of the arm64 development effort, let's not loose sight of it as
>> obviously, this is not working properly just yet.
> 
> I believe the proposed solution in this patch series is just that. I am not
> sure what the alternatives are. The alternative suggested was to reuse

Look at the responses from myself and from Rob to patch 0.  No one responded
to our comments.

-Frank


> pre-existing dt-bindings for dependency based probe re-ordering and resolution.
> 
> However, it seems we had no way to *really* check if these dependencies are
> the real. So, a device may or may not actually depend on the other device for
> probe / initialization when the dependency is mentioned in it's dt node. From
> DT's point of view, there is no way to tell this ..
> 
> I don't know how this is handled in x86. With DT, I don't see how we can do
> this unless DT dependencies are _really_ tied with runtime dependencies (The
> cycles would have been apparent if that was the case.
> 
> Honestly, the "depends-on" property suggested here just piles on to the
> existing state. So, it is somewhat doubling the exiting bindings. It says,
> you must use depends-on property to define probe / initialization dependency.
> The existing bindings like 'clock', 'interrupt', '*-supply' do not enforce
> that right now, so you will have device nodes that have these bindings right
> now but don't necessarily need them for successful probe for example.
> 
>>
>> It just seems that Android is the first one to actually try and
>> implement that goal :)
> 
> I guess :)
> 
> - ssp
> 
>>
>> thanks,
>>
>> greg k-h
>