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Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy
 for a long time
To:     Thierry Reding <thierry.reding@gmail.com>,
        Wolfram Sang <wsa@the-dreams.de>
Cc:     Jon Hunter <jonathanh@nvidia.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Manikanta Maddireddy <mmaddireddy@nvidia.com>,
        Vidya Sagar <vidyas@nvidia.com>, linux-i2c@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <127a2c32-e5fb-2944-3062-361b276490c0@gmail.com>
Date:   Mon, 27 Apr 2020 19:02:05 +0300
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27.04.2020 18:32, Thierry Reding пишет:
> On Mon, Apr 27, 2020 at 12:50:29PM +0200, Thierry Reding wrote:
>> On Mon, Apr 27, 2020 at 12:35:53PM +0200, Wolfram Sang wrote:
>>> On Mon, Apr 27, 2020 at 12:07:19PM +0300, Dmitry Osipenko wrote:
>>>> 27.04.2020 11:44, Wolfram Sang пишет:
>>>>>
>>>>>> Wolfram, can you revert the following two patches for v5.7, please?
>>>>>>
>>>>>> 	8814044fe0fa i2c: tegra: Synchronize DMA before termination
>>>>
>>>> This patch has nothing to do with your trouble, why do you want to
>>>> revert it?
>>>
>>> I'll wait some more before pushing out, so you can discuss it.
>>
>> Okay, let me run a quick test with that second patch still applied to
>> make sure it really is harmless.
> 
> Alright, I tested v5.7-rc3 with this patch reverted:
> 
> 	a900aeac2537 i2c: tegra: Better handle case where CPU0 is busy for a long time
> 
> and the results came back positive, so I think we can leave patch:
> 
> 	8814044fe0fa i2c: tegra: Synchronize DMA before termination
> 
> in. But then again, I see that Dmitry posted this yesterday:
> 
> 	https://lkml.org/lkml/2020/4/26/481
> 
> which seems like it would be related to this and potentially be a
> follow-up fix for some corner cases?

This is a follow-up to my previous message in this thread:

https://lkml.org/lkml/2020/4/23/792

> So I'm not sure how well this whole set has been tested yet.

It depends on what you're meaning by the testing. We have some
yet-out-of-tree real-world devices that are using APBDMA for Bluetooth,
Audio, I2C (touchscreens) and etc peripherals. These devices were using
the DMA patches before they were posted to the ML.

> Maybe a better solution would be for the DMA synchronization patch to go
> into the 5.8 queue instead to make sure we get more testing cycles.

It should be fine to re-queue the patches for 5.8. I'm just a bit afraid
that if patches are simply dropped now, then you won't get back to it
for a year or so ;)