linux-kernel - Re: [PATCH v8 3/3] dmaengine: pl330: Don't require irq-safe runtime PM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-id: <ea75ca9a-efc0-2d47-d6ef-fd32e675db49@samsung.com>
Date:   Tue, 14 Feb 2017 08:50:43 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Vinod Koul <vinod.koul@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        dmaengine@...r.kernel.org,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Arnd Bergmann <arnd@...db.de>, Inki Dae <inki.dae@...sung.com>
Subject: Re: [PATCH v8 3/3] dmaengine: pl330: Don't require irq-safe runtime PM

Hi Vinod,


On 2017-02-13 16:47, Vinod Koul wrote:
> On Mon, Feb 13, 2017 at 04:32:32PM +0100, Ulf Hansson wrote:
>> [...]
>>
>>>> Although, I don't know of other examples, besides the runtime PM use
>>>> case, where non-atomic channel prepare/unprepare would make sense. Do
>>>> you?
>>> The primary ask for that has been to enable runtime_pm for drivers. It's not
>>> a new ask, but we somehow haven't gotten around to do it.
>> Okay, I see.
>>
>>>>> As I said earlier, if we want to solve that problem a better idea is to
>>>>> actually split the prepare as we discussed in [1]
>>>>>
>>>>> This way we can get a non atomic descriptor allocate/prepare and release.
>>>>> Yes we need to redesign the APIs to solve this, but if you guys are up for
>>>>> it, I think we can do it and avoid any further round abouts :)
>>>> Adding/re-designing dma APIs is a viable option to solve the runtime PM case.
>>>>
>>>> Changes would be needed for all related dma client drivers as well,
>>>> although if that's what we need to do - let's do it.
>>> Yes, but do bear in mind that some cases do need atomic prepare. The primary
>>> cases for DMA had that in mind and also submitting next transaction from the
>>> callback (tasklet) context, so that won't go away.
>>>
>>> It would help in other cases where clients know that they will not be in
>>> atomic context so we provide additional non-atomic "allocation" followed by
>>> prepare, so that drivers can split the work among these and people can do
>>> runtime_pm and other things..
>> That for sharing the details.
>>
>> It seems like some dma expert really need to be heavily involved if we
>> ever are going to complete this work. :-)
> Sure, I will help out :)
>
> If anyone of you are in Portland next week, then we can discuss these f2f. I
> will try taking a stab at the new API design next week.

I'm not going to Portland, but I hope that you will have a fruitful 
discussion
there.

[...]

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland