From: Jon Hunter <jonathanh@nvidia.com>
To: Jose Abreu <Jose.Abreu@synopsys.com>,
Robin Murphy <robin.murphy@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-stm32@st-md-mailman.stormreply.com"
<linux-stm32@st-md-mailman.stormreply.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>
Cc: Joao Pinto <Joao.Pinto@synopsys.com>,
Alexandre Torgue <alexandre.torgue@st.com>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Chen-Yu Tsai <wens@csie.org>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
linux-tegra <linux-tegra@vger.kernel.org>,
Giuseppe Cavallaro <peppe.cavallaro@st.com>,
"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH net-next 3/3] net: stmmac: Introducing support for Page Pool
Date: Mon, 29 Jul 2019 22:33:04 +0100 [thread overview]
Message-ID: <8a60361f-b914-93ef-0d80-92ae4ad8b808@nvidia.com> (raw)
In-Reply-To: <MN2PR12MB3279ABF628C52883021123C5D3DD0@MN2PR12MB3279.namprd12.prod.outlook.com>
On 29/07/2019 15:08, Jose Abreu wrote:
...
>>> Hi Catalin and Will,
>>>
>>> Sorry to add you in such a long thread but we are seeing a DMA issue
>>> with stmmac driver in an ARM64 platform with IOMMU enabled.
>>>
>>> The issue seems to be solved when buffers allocation for DMA based
>>> transfers are *not* mapped with the DMA_ATTR_SKIP_CPU_SYNC flag *OR*
>>> when IOMMU is disabled.
>>>
>>> Notice that after transfer is done we do use
>>> dma_sync_single_for_{cpu,device} and then we reuse *the same* page for
>>> another transfer.
>>>
>>> Can you please comment on whether DMA_ATTR_SKIP_CPU_SYNC can not be used
>>> in ARM64 platforms with IOMMU ?
>>
>> In terms of what they do, there should be no difference on arm64 between:
>>
>> dma_map_page(..., dir);
>> ...
>> dma_unmap_page(..., dir);
>>
>> and:
>>
>> dma_map_page_attrs(..., dir, DMA_ATTR_SKIP_CPU_SYNC);
>> dma_sync_single_for_device(..., dir);
>> ...
>> dma_sync_single_for_cpu(..., dir);
>> dma_unmap_page_attrs(..., dir, DMA_ATTR_SKIP_CPU_SYNC);
>>
>> provided that the first sync covers the whole buffer and any subsequent
>> ones cover at least the parts of the buffer which may have changed. Plus
>> for coherent hardware it's entirely moot either way.
>
> Thanks for confirming. That's indeed what stmmac is doing when buffer is
> received by syncing the packet size to CPU.
>
>>
>> Given Jon's previous findings, I would lean towards the idea that
>> performing the extra (redundant) cache maintenance plus barrier in
>> dma_unmap is mostly just perturbing timing in the same way as the debug
>> print which also made things seem OK.
>
> Mikko said that Tegra186 is not coherent so we have to explicit flush
> pipeline but I don't understand why sync_single() is not doing it ...
>
> Jon, can you please remove *all* debug prints, hacks, etc ... and test
> this one in attach with plain -net tree ?
So far I have just been testing on the mainline kernel branch. The issue
still persists after applying this on mainline. I can test on the -net
tree, but I am not sure that will make a difference.
Cheers
Jon
--
nvpublic
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next prev parent reply other threads:[~2019-07-29 21:33 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-03 10:37 [PATCH net-next 0/3] net: stmmac: Some performance improvements and a fix Jose Abreu
2019-07-03 10:37 ` [PATCH net-next 1/3] net: stmmac: Implement RX Coalesce Frames setting Jose Abreu
2019-07-03 20:41 ` Jakub Kicinski
2019-07-03 10:37 ` [PATCH net-next 2/3] net: stmmac: Fix descriptors address being in > 32 bits address space Jose Abreu
2019-07-03 10:37 ` [PATCH net-next 3/3] net: stmmac: Introducing support for Page Pool Jose Abreu
2019-07-03 10:40 ` Jose Abreu
2019-07-04 9:39 ` Jesper Dangaard Brouer
2019-07-04 14:45 ` Jose Abreu
2019-07-04 15:09 ` Jesper Dangaard Brouer
2019-07-04 15:18 ` Jose Abreu
2019-07-04 15:33 ` Jesper Dangaard Brouer
2019-07-04 9:48 ` Jesper Dangaard Brouer
2019-07-04 10:00 ` Jesper Dangaard Brouer
2019-07-04 10:13 ` Jose Abreu
2019-07-04 11:11 ` Ilias Apalodimas
2019-07-04 11:54 ` Jesper Dangaard Brouer
2019-07-04 12:04 ` Ilias Apalodimas
2019-07-04 12:59 ` Jose Abreu
2019-07-04 13:06 ` Ilias Apalodimas
2019-07-04 10:30 ` Ilias Apalodimas
2019-07-04 12:14 ` Arnd Bergmann
2019-07-04 12:49 ` Ilias Apalodimas
2019-07-17 18:58 ` Jon Hunter
2019-07-18 7:29 ` Jose Abreu
2019-07-18 7:48 ` Jose Abreu
2019-07-18 9:16 ` Jon Hunter
2019-07-19 7:51 ` Jose Abreu
2019-07-19 8:37 ` Jon Hunter
2019-07-19 8:44 ` Jose Abreu
2019-07-19 8:49 ` Jon Hunter
2019-07-19 10:25 ` Jose Abreu
2019-07-19 12:28 ` Jose Abreu
2019-07-19 13:33 ` Jon Hunter
2019-07-19 12:30 ` Jon Hunter
2019-07-19 12:32 ` Jose Abreu
[not found] ` <25512348-5b98-aeb7-a6fb-f90376e66a84@nvidia.com>
2019-07-22 7:23 ` Jose Abreu
2019-07-22 9:37 ` Jon Hunter
2019-07-22 9:47 ` Jose Abreu
2019-07-22 9:57 ` Jose Abreu
2019-07-22 10:27 ` Jon Hunter
2019-07-22 10:18 ` Ilias Apalodimas
2019-07-22 11:11 ` Lars Persson
2019-07-22 11:39 ` Jose Abreu
2019-07-22 12:05 ` Jon Hunter
2019-07-22 14:04 ` Jose Abreu
2019-07-23 8:14 ` Jose Abreu
2019-07-23 10:01 ` Jon Hunter
2019-07-23 10:07 ` Jose Abreu
2019-07-23 10:29 ` Robin Murphy
2019-07-23 11:22 ` Jose Abreu
2019-07-23 12:09 ` Jon Hunter
2019-07-23 13:19 ` Robin Murphy
2019-07-23 21:39 ` Jon Hunter
2019-07-24 10:03 ` Robin Murphy
2019-07-23 18:51 ` David Miller
2019-07-24 8:54 ` Ilias Apalodimas
2019-07-24 9:43 ` Jose Abreu
2019-07-24 9:53 ` Ilias Apalodimas
2019-07-24 10:04 ` Jose Abreu
2019-07-24 11:10 ` Jon Hunter
2019-07-24 11:34 ` Jose Abreu
2019-07-24 11:58 ` Jon Hunter
2019-07-25 7:44 ` Jose Abreu
2019-07-25 9:45 ` Jon Hunter
2019-07-25 11:39 ` Ilias Apalodimas
2019-07-23 10:38 ` Jon Hunter
2019-07-23 10:49 ` Jose Abreu
2019-07-23 11:58 ` Jon Hunter
2019-07-23 12:51 ` Jose Abreu
2019-07-23 13:34 ` Jon Hunter
2019-07-29 9:45 ` Mikko Perttunen
2019-07-25 13:20 ` Jon Hunter
2019-07-25 13:26 ` Jose Abreu
2019-07-25 14:25 ` Jon Hunter
2019-07-25 15:12 ` Jose Abreu
2019-07-26 14:11 ` Jon Hunter
2019-07-27 15:56 ` Jose Abreu
2019-07-29 8:16 ` Jose Abreu
2019-07-29 10:55 ` Jon Hunter
2019-07-29 11:29 ` Jose Abreu
2019-07-29 11:52 ` Robin Murphy
2019-07-29 14:08 ` Jose Abreu
2019-07-29 21:33 ` Jon Hunter [this message]
2019-07-30 9:39 ` Jose Abreu
2019-07-30 13:36 ` Jon Hunter
2019-07-30 13:58 ` Jose Abreu
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