From: Tomasz Figa <tfiga@chromium.org>
To: Yingjoe Chen <yingjoe.chen@mediatek.com>
Cc: "Joerg Roedel" <joro@8bytes.org>,
"Mark Rutland" <mark.rutland@arm.com>,
devicetree@vger.kernel.org, srv_heupstream@mediatek.com,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will.deacon@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
iommu@lists.linux-foundation.org,
"Rob Herring" <robh+dt@kernel.org>,
"Daniel Kurtz" <djkurtz@google.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"Sasha Hauer" <kernel@pengutronix.de>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
linux-mediatek@lists.infradead.org,
"Robin Murphy" <robin.murphy@arm.com>,
"Yong Wu (吴勇)" <yong.wu@mediatek.com>,
"Lucas Stach" <l.stach@pengutronix.de>
Subject: Re: [PATCH 2/5] iommu/mediatek: Add mt8173 IOMMU driver
Date: Tue, 10 Mar 2015 13:06:31 +0900 [thread overview]
Message-ID: <CAAFQd5BSdAqT00YPYHn6J+Ps1VzhXLhZrronsPXVGPrAir62Qw@mail.gmail.com> (raw)
In-Reply-To: <1425958907.4871.102.camel@mtksdaap41>
On Tue, Mar 10, 2015 at 12:41 PM, Yingjoe Chen
<yingjoe.chen@mediatek.com> wrote:
> On Tue, 2015-03-10 at 02:00 +0900, Tomasz Figa wrote:
>> On Mon, Mar 9, 2015 at 11:46 PM, Yingjoe Chen <yingjoe.chen@mediatek.com> wrote:
>> > On Mon, 2015-03-09 at 20:11 +0900, Tomasz Figa wrote:
>> > <...>
>> >> > +/*
>> >> > + * pimudev is a global var for dma_alloc_coherent.
>> >> > + * It is not accepatable, we will delete it if "domain_alloc" is enabled
>> >> > + */
>> >> > +static struct device *pimudev;
>> >>
>> >> This is indeed not acceptable. Could you replace dma_alloc_coherent()
>> >> with something that doesn't require device pointer, e.g.
>> >> alloc_pages()? (Although that would require you to handle cache
>> >> maintenance in the driver, due to cached memory allocated.) I need to
>> >> think about a better solution for this.
>> >
>> > Hi,
>> >
>> > For 2nd level page table, we use cached memory now. Currently we are
>> > using __dma_flush_range to flush the cache, which is also unacceptable.
>> >
>> > For proper cache management, we'll need to use dma_map_single or
>> > dma_sync_*, which still need a deivce*.
>>
>> Looking at how already mainlined drivers do this, they either use
>> dmac_flush_range()
>> (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/msm_iommu.c?id=refs/tags/v4.0-rc3#n80)
>> or directly __cpuc_flush_dcache_area() and outer_flush_range()
>> (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/rockchip-iommu.c?id=refs/tags/v4.0-rc3#n93).
>
> Hi,
>
> These only exist in arch/arm, not arm64. I think we should avoid using
> API start with __ in drivers. This driver might be used in both
> arm/arm64, I think the only option for us is DMA APIs.
>
> Actually, I'm thinking that we should change to use coherent memory for
> 2nd level page table as well and totally skip the cache flush. It seems
> dma_pool_create is suitable to replace kmem_cache we are using right
> now. However it still need a device*, which we have to fix anyway.
That sounds like a reasonable option, because this is what we have DMA
mapping API for.
Do you expect to have more than one M4U block inside a SoC? Maybe this
static variable actually isn't that bad, with a comment added
explaining that there is always only one such block and that a rework
will be needed if future SoCs will have more.
Best regards,
Tomasz
next prev parent reply other threads:[~2015-03-10 4:06 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-06 10:48 [RFC PATCH 0/5] MT8173 IOMMU support yong.wu
2015-03-06 10:48 ` [PATCH 1/5] soc: mediatek: Add SMI driver yong.wu
2015-03-06 11:30 ` Paul Bolle
2015-03-09 11:57 ` Yong Wu
2015-03-09 17:59 ` Paul Bolle
2015-03-09 21:54 ` Arnd Bergmann
2015-03-10 6:17 ` Yingjoe Chen
2015-03-09 3:26 ` Yingjoe Chen
2015-03-09 21:56 ` Arnd Bergmann
2015-03-10 6:27 ` Yingjoe Chen
2015-03-10 9:05 ` Arnd Bergmann
2015-03-10 9:24 ` Lucas Stach
2015-03-09 11:03 ` Sascha Hauer
2015-03-06 10:48 ` [PATCH 2/5] iommu/mediatek: Add mt8173 IOMMU driver yong.wu
2015-03-06 10:58 ` Will Deacon
2015-03-09 12:11 ` Yong Wu
2015-03-17 15:14 ` Will Deacon
2015-03-06 17:15 ` Mitchel Humpherys
2015-03-09 12:16 ` Yong Wu
2015-03-09 16:57 ` Mitchel Humpherys
2015-03-08 4:12 ` Tomasz Figa
2015-03-12 14:16 ` Yong Wu
2015-03-09 8:24 ` Daniel Kurtz
2015-03-09 11:11 ` Tomasz Figa
2015-03-09 14:46 ` Yingjoe Chen
2015-03-09 17:00 ` Tomasz Figa
2015-03-10 3:41 ` Yingjoe Chen
2015-03-10 4:06 ` Tomasz Figa [this message]
2015-03-11 10:53 ` Tomasz Figa
2015-03-18 11:22 ` Yong Wu
2015-03-20 19:14 ` Robin Murphy
2015-04-14 6:50 ` Yong Wu
2015-03-27 9:41 ` Tomasz Figa
2015-04-14 6:31 ` Yong Wu
2015-04-15 2:20 ` Tomasz Figa
2015-04-15 7:06 ` Yong Wu
2015-04-15 7:41 ` Tomasz Figa
2015-04-29 6:23 ` Yong Wu
2015-03-06 10:48 ` [PATCH 3/5] dt-bindings: mediatek: Add smi dts binding yong.wu
2015-03-06 11:13 ` Mark Rutland
2015-03-09 12:55 ` Yong Wu
2015-04-14 9:07 ` Yong Wu
2015-04-14 10:06 ` Mark Rutland
2015-04-14 13:49 ` Yong Wu
2015-04-14 13:55 ` Yong Wu
2015-04-14 13:56 ` Mark Rutland
2015-03-06 14:48 ` Sergei Shtylyov
2015-03-09 12:32 ` Yong Wu
2015-03-06 10:48 ` [PATCH 4/5] dt-bindings: iommu: Add binding for mediatek IOMMU yong.wu
2015-03-06 11:21 ` Mark Rutland
2015-03-09 11:30 ` Yong Wu
2015-03-06 10:48 ` [PATCH 5/5] dts: mt8173: Add iommu/smi nodes for mt8173 yong.wu
2015-03-07 15:20 ` Daniel Kurtz
2015-03-09 12:18 ` Yong Wu
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