linux-kernel - Re: [RFC PATCH 00/12] net: introduce Qualcomm IPA driver

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Date:   Wed, 7 Nov 2018 16:46:47 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Alex Elder <elder@...aro.org>
Cc:     David Miller <davem@...emloft.net>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Networking <netdev@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        syadagir@...eaurora.org, mjavid@...eaurora.org
Subject: Re: [RFC PATCH 00/12] net: introduce Qualcomm IPA driver

On Wed, Nov 7, 2018 at 1:33 AM Alex Elder <elder@...aro.org> wrote:
> The code has undergone considerable rework to prepare it for
> incorporation into upstream Linux.  Parts of it bear little
> resemblance to the original driver.  Still, some work remains
> to be done.  The current code and its design had a preliminary
> review, and some changes to the data path implementation were
> recommended.   These have not yet been addressed:
> - Use NAPI for all interfaces, not just RX (and WAN data) endpoints.
> - Do more work in the NAPI poll function, including collecting
>   completed TX requests and posting buffers for RX.
> - Do not use periodic NOP requests as a way to avoid TX interrupts.
> - The NAPI context should be associated with the hardware interrupt
>   (it is now associated with something abstracted from the hardware).
> - Use threaded interrupts, to avoid the need for using spinlocks and
>   atomic variables for synchronizing between workqueue and interrupt
>   context.
> - Have runtime power management enable and disable IPA clock and
>   interconnects.
> Many thanks to Arnd Bergmann, Ilias Apalodimas, and Bjorn Andersson
> for their early feedback.

Thanks for getting the current version out even with the long TODO
list. I've had my first deeper look at some of the patches and found
a few more things that likely require substantial rework. I also think
there is still significant room for simplifying it further, and getting
better performance out of it in the process.

Also, despite the criticism in my patch review, I have to say you've
done a great job at cutting out a lot of the things that were present
in the past, it's good to see that you have come this far with the
cleanup!

      Arnd