From: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Johannes Berg <johannes@sipsolutions.net>,
Alex Elder <elder@linaro.org>,
abhishek.esse@gmail.com, Ben Chan <benchan@google.com>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
cpratapa@codeaurora.org, David Miller <davem@davemloft.net>,
Dan Williams <dcbw@redhat.com>, DTML <devicetree@vger.kernel.org>,
Eric Caruso <ejcaruso@google.com>,
evgreen@chromium.org,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-arm-msm@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-soc@vger.kernel.org, Networking <netdev@vger.kernel.org>,
syadagir@codeaurora.org
Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver
Date: Tue, 18 Jun 2019 15:15:42 -0600 [thread overview]
Message-ID: <6c70950d0c78bc02a3d016918ec3929e@codeaurora.org> (raw)
In-Reply-To: <CAK8P3a2onXpxiE4y9PzRwuPM2dh=h_BKz7Eb0=LLPgBbZoK1bQ@mail.gmail.com>
On 2019-06-18 14:55, Arnd Bergmann wrote:
> On Tue, Jun 18, 2019 at 10:36 PM Johannes Berg
> <johannes@sipsolutions.net> wrote:
>>
>> On Tue, 2019-06-18 at 21:59 +0200, Arnd Bergmann wrote:
>> >
>> > From my understanding, the ioctl interface would create the lower
>> > netdev after talking to the firmware, and then user space would use
>> > the rmnet interface to create a matching upper-level device for that.
>> > This is an artifact of the strong separation of ipa and rmnet in the
>> > code.
>>
>> Huh. But if rmnet has muxing, and IPA supports that, why would you
>> ever
>> need multiple lower netdevs?
>
> From my reading of the code, there is always exactly a 1:1 relationship
> between an rmnet netdev an an ipa netdev. rmnet does the encapsulation/
> decapsulation of the qmap data and forwards it to the ipa netdev,
> which then just passes data through between a hardware queue and
> its netdevice.
>
There is a n:1 relationship between rmnet and IPA.
rmnet does the de-muxing to multiple netdevs based on the mux id
in the MAP header for RX packets and vice versa.
> [side note: on top of that, rmnet also does "aggregation", which may
> be a confusing term that only means transferring multiple frames
> at once]
>
>> > ipa definitely has multiple hardware queues, and the Alex'
>> > driver does implement the data path on those, just not the
>> > configuration to enable them.
>>
>> OK, but perhaps you don't actually have enough to use one for each
>> session?
>
> I'm lacking the terminology here, but what I understood was that
> the netdev and queue again map to a session.
>
>> > Guessing once more, I suspect the the XON/XOFF flow control
>> > was a workaround for the fact that rmnet and ipa have separate
>> > queues. The hardware channel on IPA may fill up, but user space
>> > talks to rmnet and still add more frames to it because it doesn't
>> > know IPA is busy.
>> >
>> > Another possible explanation would be that this is actually
>> > forwarding state from the base station to tell the driver to
>> > stop sending data over the air.
>>
>> Yeah, but if you actually have a hardware queue per upper netdev then
>> you don't really need this - you just stop the netdev queue when the
>> hardware queue is full, and you have flow control automatically.
>>
>> So I really don't see any reason to have these messages going back and
>> forth unless you plan to have multiple sessions muxed on a single
>> hardware queue.
>
Hardware may flow control specific PDNs (rmnet interfaces) based on QoS
-
not necessarily only in case of hardware queue full.
> Sure, I definitely understand what you mean, and I agree that would
> be the right way to do it. All I said is that this is not how it was
> done
> in rmnet (this was again my main concern about the rmnet design
> after I learned it was required for ipa) ;-)
>
> Arnd
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2019-06-18 21:15 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-31 3:53 [PATCH v2 00/17] net: introduce Qualcomm IPA driver Alex Elder
2019-05-31 3:53 ` [PATCH v2 01/17] bitfield.h: add FIELD_MAX() and field_max() Alex Elder
2019-05-31 3:53 ` [PATCH v2 02/17] dt-bindings: soc: qcom: add IPA bindings Alex Elder
2019-06-10 22:08 ` Rob Herring
2019-06-11 2:11 ` Alex Elder
2019-07-03 15:09 ` Alex Elder
2019-05-31 3:53 ` [PATCH v2 03/17] soc: qcom: ipa: main code Alex Elder
2019-05-31 21:50 ` David Miller
2019-05-31 22:25 ` Alex Elder
2019-05-31 3:53 ` [PATCH v2 04/17] soc: qcom: ipa: configuration data Alex Elder
2019-05-31 3:53 ` [PATCH v2 05/17] soc: qcom: ipa: clocking, interrupts, and memory Alex Elder
2019-05-31 3:53 ` [PATCH v2 06/17] soc: qcom: ipa: GSI headers Alex Elder
2019-05-31 3:53 ` [PATCH v2 07/17] soc: qcom: ipa: the generic software interface Alex Elder
2019-05-31 3:53 ` [PATCH v2 08/17] soc: qcom: ipa: GSI transactions Alex Elder
2019-05-31 3:53 ` [PATCH v2 09/17] soc: qcom: ipa: IPA interface to GSI Alex Elder
2019-05-31 3:53 ` [PATCH v2 10/17] soc: qcom: ipa: IPA endpoints Alex Elder
2019-05-31 3:53 ` [PATCH v2 11/17] soc: qcom: ipa: immediate commands Alex Elder
2019-05-31 3:53 ` [PATCH v2 12/17] soc: qcom: ipa: IPA network device and microcontroller Alex Elder
2019-05-31 3:53 ` [PATCH v2 13/17] soc: qcom: ipa: AP/modem communications Alex Elder
2019-05-31 3:53 ` [PATCH v2 14/17] soc: qcom: ipa: support build of IPA code Alex Elder
2019-05-31 3:53 ` [PATCH v2 15/17] MAINTAINERS: add entry for the Qualcomm IPA driver Alex Elder
2019-05-31 3:53 ` [PATCH v2 16/17] arm64: dts: sdm845: add IPA information Alex Elder
2019-05-31 3:53 ` [PATCH v2 17/17] arm64: defconfig: enable build of IPA code Alex Elder
2019-05-31 14:58 ` [PATCH v2 00/17] net: introduce Qualcomm IPA driver Dan Williams
2019-05-31 16:36 ` Alex Elder
2019-05-31 19:19 ` Arnd Bergmann
2019-05-31 20:47 ` Alex Elder
2019-05-31 21:12 ` Arnd Bergmann
2019-05-31 22:08 ` Alex Elder
2019-06-07 17:43 ` Alex Elder
2019-05-31 23:33 ` Bjorn Andersson
2019-05-31 23:59 ` Subash Abhinov Kasiviswanathan
2019-06-03 10:04 ` Arnd Bergmann
2019-06-03 13:32 ` Alex Elder
2019-06-04 8:13 ` Arnd Bergmann
2019-06-04 15:18 ` Dan Williams
2019-06-04 20:04 ` Arnd Bergmann
2019-06-04 21:29 ` Dan Williams
2019-06-06 17:42 ` Alex Elder
2019-06-11 8:12 ` Johannes Berg
2019-06-11 11:56 ` Arnd Bergmann
2019-06-11 15:53 ` Dan Williams
2019-06-11 16:52 ` Subash Abhinov Kasiviswanathan
2019-06-11 17:22 ` Dan Williams
2019-06-12 8:31 ` Arnd Bergmann
2019-06-12 14:27 ` Dan Williams
2019-06-12 15:06 ` Arnd Bergmann
2019-06-17 11:42 ` Johannes Berg
2019-06-17 12:25 ` Johannes Berg
2019-06-18 15:20 ` Alex Elder
2019-06-18 18:06 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-25 14:14 ` Johannes Berg
2019-06-26 13:36 ` Alex Elder
2019-06-26 17:55 ` Johannes Berg
2019-06-18 18:48 ` Johannes Berg
2019-06-24 16:21 ` Alex Elder
2019-06-18 13:45 ` Alex Elder
2019-06-18 19:03 ` Johannes Berg
2019-06-18 20:09 ` Arnd Bergmann
2019-06-18 20:15 ` Johannes Berg
2019-06-18 20:33 ` Arnd Bergmann
2019-06-18 20:39 ` Johannes Berg
2019-06-18 21:06 ` Arnd Bergmann
2019-06-19 20:56 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-24 16:40 ` Arnd Bergmann
2019-06-25 14:19 ` Johannes Berg
2019-06-26 13:39 ` Alex Elder
2019-06-26 13:58 ` Arnd Bergmann
2019-06-26 17:48 ` Johannes Berg
2019-06-26 17:45 ` Johannes Berg
2019-06-26 13:51 ` Alex Elder
2019-06-17 11:28 ` Johannes Berg
2019-06-18 13:16 ` Alex Elder
2019-06-18 13:48 ` Arnd Bergmann
2019-06-18 19:14 ` Johannes Berg
2019-06-18 19:59 ` Arnd Bergmann
2019-06-18 20:36 ` Johannes Berg
2019-06-18 20:55 ` Arnd Bergmann
2019-06-18 21:02 ` Johannes Berg
2019-06-18 21:15 ` Subash Abhinov Kasiviswanathan [this message]
2019-06-19 12:23 ` Arnd Bergmann
2019-06-19 18:47 ` Subash Abhinov Kasiviswanathan
2019-06-20 1:25 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-17 12:14 ` Johannes Berg
2019-06-18 14:00 ` Alex Elder
2019-06-18 19:22 ` Johannes Berg
2019-06-24 16:21 ` Alex Elder
2019-06-03 14:50 ` Dan Williams
2019-06-03 14:54 ` Dan Williams
2019-06-03 15:52 ` Alex Elder
2019-06-03 16:18 ` Dan Williams
2019-06-03 19:04 ` Subash Abhinov Kasiviswanathan
2019-06-04 15:21 ` Dan Williams
2019-05-31 23:27 ` Bjorn Andersson
2019-06-10 2:44 ` Alex Elder
2019-06-24 16:30 ` WWAN Controller Framework (was IPA [PATCH v2 00/17]) Alex Elder
2019-06-24 17:06 ` Alex Elder
2019-06-25 14:34 ` Johannes Berg
2019-06-26 13:40 ` Alex Elder
2019-06-26 17:58 ` Johannes Berg
2019-06-24 19:54 ` Dan Williams
2019-06-24 21:16 ` Alex Elder
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