From: Sean Anderson <sean.anderson@seco.com>
To: "Michal Simek" <michal.simek@xilinx.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
Rob Herring <robh+dt@kernel.org>,
Thierry Reding <thierry.reding@gmail.com>,
Alvaro Gamez <alvaro.gamez@hazent.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Lee Jones <lee.jones@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
kernel@pengutronix.de
Subject: Re: [PATCH v3 2/2] clocksource: Add support for Xilinx AXI Timer
Date: Fri, 18 Jun 2021 17:24:09 -0400 [thread overview]
Message-ID: <48f972d5-8690-7850-317b-59bb9680d8f9@seco.com> (raw)
In-Reply-To: <64318c16-780c-336a-8580-e70c91b71cbf@xilinx.com>
On 6/16/21 8:12 AM, Michal Simek wrote:
> Hi Uwe,
>
> On 5/25/21 8:11 AM, Uwe Kleine-König wrote:
>> Hello Sean, hello Michal,
>>
>> On Mon, May 24, 2021 at 09:00:51AM +0200, Michal Simek wrote:
>>> On 5/20/21 10:13 PM, Sean Anderson wrote:
>>>> On 5/19/21 3:24 AM, Michal Simek wrote:
>>>>> On 5/18/21 12:15 AM, Sean Anderson wrote:
>>>>>> This could be deprecated, but cannot be removed since existing device
>>>>>> trees (e.g. qemu) have neither clocks nor clock-frequency properties.
>>>>>
>>>>> Rob: Do we have any obligation to keep properties for other projects?
>>
>> If a binding is in the wild and used to be documented, it has to stay.
>>
>>>>>>> 4. Make driver as module
>>>>>>> 5. Do whatever changes you want before adding pwm support
>>>>>>> 6. Extend DT binding doc for PWM support
>>>>>>> 7. Add PWM support
>>>>>>
>>>>>> Frankly, I am inclined to just leave the microblaze timer as-is. The PWM
>>>>>> driver is completely independent. I have already put too much effort into
>>>>>> this driver, and I don't have the energy to continue working on the
>>>>>> microblaze timer.
>>>>>
>>>>> I understand. I am actually using axi timer as pwm driver in one of my
>>>>> project but never had time to upstream it because of couple of steps above.
>>>>> We need to do it right based on steps listed above. If this is too much
>>>>> work it will have to wait. I will NACK all attempts to add separate
>>>>> driver for IP which we already support in the tree.
>>>>
>>>> 1. Many timers have separate clocksource and PWM drivers. E.g. samsung,
>>>> renesas TPU, etc. It is completely reasonable to keep separate
>>>> drivers for these purposes. There is no Linux requirement that each
>>>> device have only one driver, especially if it has multiple functions
>>>> or ways to be configured.
>>>
>>> It doesn't mean that it was done properly and correctly. Code
>>> duplication is bad all the time.
>>
>> IMHO it's not so much about code duplication. Yes, code duplication is
>> bad and should be prevented if possible. But it's more important to not
>> introduce surprises. So I think it should be obvious from reading the
>> device tree source which timer is used to provide the PWM. I don't care
>> much if this is from an extra property (like xilinx,provide-pwm),
>> overriding the compatible or some other explicit mechanism. IIUC in this
>> suggested patch the selection is implicit and so this isn't so nice.
>>
>>>> 2. If you want to do work on a driver, I'm all for it. However, if you
>>>> have not yet submitted that work to the list, you should not gate
>>>> other work behind it. Saying that X feature must be gated behind Y
>>>> *even if X works completely independently of Y* is just stifling
>>>> development.
>>>
>>> I gave you guidance how I think this should be done. I am not gating you
>>> from this work. Your patch is not working on Microblaze arch which is
>>> what I maintain. And I don't want to go the route that we will have two
>>> drivers for the same IP without integration. We were there in past and
>>> it is just pain.
>>> I am expecting that PWM guys will guide how this should be done
>>> properly. I haven't heard any guidance on this yet.
>>> Thierry/Uwe: Any comment?
>>
>> Not sure I can and want to provide guidance here. This is not Perl, but
>> still TIMTOWTDI. If it was me who cared here, I'd look into the
>> auxiliary bus (Documentation/driver-api/auxiliary_bus.rst) to check if
>> it can help to solve this problem.
>
> I recently got patches for cadence TTC driver
> (drivers/clocksource/timer-cadence-ttc.c) for PWM support too. It is the
> second and very similar case. This driver is used on Zynq as clock
> source and can be also use as PWM. I can't believe that there are no
> other examples how to deal with these timers which are used for PWM
> generation.
>
The approach I took in v4 is that probe functions and driver callbacks
live in drivers/timer and drivers/pwm, and common functions live in
drivers/mfd (although I may move them to drivers/timer since Lee Jones
doesn't like them there).
I would greatly appreciate if you could review v4. It has been on the
list for three weeks now with no comments from either you or Uwe.
--Sean
next prev parent reply other threads:[~2021-06-18 21:24 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 19:12 [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer Sean Anderson
2021-05-11 19:12 ` [PATCH v3 2/2] clocksource: Add support for " Sean Anderson
2021-05-11 19:19 ` Sean Anderson
2021-05-12 8:31 ` kernel test robot
2021-05-14 8:59 ` Michal Simek
2021-05-14 14:40 ` Sean Anderson
2021-05-17 7:54 ` Michal Simek
2021-05-17 22:15 ` Sean Anderson
2021-05-19 7:24 ` Michal Simek
2021-05-20 20:13 ` Sean Anderson
2021-05-24 7:00 ` Michal Simek
2021-05-24 18:34 ` Sean Anderson
2021-05-25 6:11 ` Uwe Kleine-König
2021-05-25 14:30 ` Sean Anderson
2021-06-16 12:12 ` Michal Simek
2021-06-18 21:24 ` Sean Anderson [this message]
2021-06-24 16:25 ` Michal Simek
2021-05-12 18:35 ` [PATCH v3 1/2] dt-bindings: pwm: Add " Rob Herring
2021-05-13 2:16 ` Rob Herring
2021-05-13 14:33 ` Sean Anderson
2021-05-13 15:28 ` Sean Anderson
2021-05-13 20:43 ` Rob Herring
2021-05-13 21:01 ` Sean Anderson
2021-05-14 8:50 ` Michal Simek
2021-05-14 17:13 ` Sean Anderson
2021-05-17 8:28 ` Michal Simek
2021-05-17 14:40 ` Sean Anderson
2021-05-17 14:49 ` Michal Simek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=48f972d5-8690-7850-317b-59bb9680d8f9@seco.com \
--to=sean.anderson@seco.com \
--cc=alvaro.gamez@hazent.com \
--cc=daniel.lezcano@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=kernel@pengutronix.de \
--cc=lee.jones@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=michal.simek@xilinx.com \
--cc=robh+dt@kernel.org \
--cc=tglx@linutronix.de \
--cc=thierry.reding@gmail.com \
--cc=u.kleine-koenig@pengutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).