From: Allen Pais <apais@linux.microsoft.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "David Laight" <David.Laight@aculab.com>,
"Linus Walleij" <linus.walleij@linaro.org>,
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Subject: Re: [RFC 1/1] drivers/dma/*: replace tasklets with workqueue
Date: Wed, 25 May 2022 11:04:11 -0700 [thread overview]
Message-ID: <45597969-0419-4CEE-B80C-4D2917943837@linux.microsoft.com> (raw)
In-Reply-To: <CAK8P3a0mOEMW3N7HB7zTAbqKJMu_RusivjxwuU7_E+O1vGHOEw@mail.gmail.com>
>>
>> Thank you Linus, Arnd, Vincent and David for the feedback.
>>
>> This is a lot more than a just conversion of API’s. I am in the process
>> Of replacing tasklets with threaded irq’s and hopefully that should be
>> A better solution than using workqueues.
>
> I don't think that is much better for the case of the DMA engine
> callbacks than the work queue, the problem I pointed out here
> is scheduling into task context, which may be too expensive
> in some cases, but whether it is or not depends on the slave
> driver, not the dmaengine driver.
Fair point. Deferring all callbacks to task context is not the ideal
Way forward. I will work on the approach you shared,
>1. add helper functions to call the callback functions from a
>tasklet locally defined in drivers/dma/dmaengine.c to allow
>deferring it from hardirq context
>2. Change all tasklets that are not part of the callback
>mechanism to work queue functions, I only see
>xilinx_dpdma_chan_err_task in the patch, but there
>may be more
>3. change all drivers to move their custom tasklets back into
>hardirq context and instead call the new helper for deferring
>the callback.
>4. Extend the dmaengine callback API to let slave drivers
>pick hardirq, tasklet or task context for the callback.
>task context can mean either a workqueue, or a threaded
>IRQ here, with the default remaining the tasklet version.
>5. Change slave drivers to pick either hardirq or task context
>depending on their requirements
>6. Remove the tasklet version.
Thanks.
>
> Even if all the slave drivers are better off using task context
> (threaded irq or workqueue), you need to look at the slave
> drivers first before you can convert the dmaengine drivers.
>
next prev parent reply other threads:[~2022-05-25 18:04 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-19 21:16 [RFC 0/1] refactor all tasklet users into other APIs Allen Pais
2022-04-19 21:16 ` [RFC 1/1] drivers/dma/*: replace tasklets with workqueue Allen Pais
2022-04-20 2:31 ` Kees Cook
2022-04-22 16:48 ` Allen Pais
2022-04-25 15:06 ` Linus Walleij
2022-04-25 23:59 ` Allen Pais
2022-04-25 15:56 ` Krzysztof Kozlowski
2022-04-25 19:55 ` Gustavo A. R. Silva
2022-04-28 9:29 ` Andy Shevchenko
[not found] ` <DA101ED8-F99F-4DCB-9CB7-370A62C44B65@linux.microsoft.com>
2022-05-12 21:54 ` Linus Walleij
2022-05-16 11:40 ` Vinod Koul
2022-04-26 0:04 ` Allen Pais
2022-04-27 2:45 ` Vinod Koul
2022-04-27 15:20 ` Dave Jiang
2022-04-27 15:58 ` Allen Pais
2022-04-27 15:53 ` Allen Pais
2022-05-25 9:24 ` Linus Walleij
2022-05-25 9:52 ` Vincent Guittot
2022-05-25 11:03 ` Arnd Bergmann
2022-05-25 15:14 ` David Laight
[not found] ` <6E248F41-6687-4F2B-B847-DB5459BA1344@linux.microsoft.com>
2022-05-25 17:48 ` Arnd Bergmann
2022-05-25 18:04 ` Allen Pais [this message]
2022-05-27 8:06 ` Vinod Koul
2022-05-27 10:59 ` Arnd Bergmann
2022-05-31 6:56 ` Vinod Koul
[not found] ` <0A9EDEDC-9E6C-47F8-89C0-48DCDD3F9DE3@linux.microsoft.com>
2022-05-31 18:02 ` Arnd Bergmann
2022-05-31 18:19 ` Allen Pais
2022-05-31 19:27 ` Arnd Bergmann
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