From: Yong Wu <yong.wu@mediatek.com>
To: Tomasz Figa <tfiga@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Mark Rutland <mark.rutland@arm.com>, <devicetree@vger.kernel.org>,
<srv_heupstream@mediatek.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Joerg Roedel <joro@8bytes.org>, 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>,
Sasha Hauer <kernel@pengutronix.de>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
<linux-mediatek@lists.infradead.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCH 2/5] iommu/mediatek: Add mt8173 IOMMU driver
Date: Tue, 14 Apr 2015 14:31:07 +0800 [thread overview]
Message-ID: <1428993067.13552.14.camel@mhfsdcap03> (raw)
In-Reply-To: <CAAFQd5DOzFmfXki8GwUC75VQFEWzxBUNUgOtSuRtV6tc27kD2A@mail.gmail.com>
Hi Tomasz,
Thanks very much for you suggestion and explain so detail.
please help check below.
On Fri, 2015-03-27 at 18:41 +0900, Tomasz Figa wrote:
> Hi Yong Wu,
>
> Sorry for long delay, I had to figure out some time to look at this again.
>
> On Wed, Mar 18, 2015 at 8:22 PM, Yong Wu <yong.wu@mediatek.com> wrote:
> >>
> >> > + imudev = piommu->dev;
> >> > +
> >> > + spin_lock_irqsave(&priv->portlock, flags);
> >>
> >> What is protected by this spinlock?
> > We will write a register of the local arbiter while config port. If
> > some modules are in the same local arbiter, it may be overwrite. so I
> > add it here.
> >>
>
> OK. Maybe it could be called larb_lock then? It would be good to have
> structures or code that should be running under this spinlock
> annotated with proper comments. And purpose of the lock documented in
> a comment as well (probably in a kerneldoc-style documentation of
> priv).
Thanks. I have move the spinlock into the smi driver, it will lock
for writing the local arbiter regsiter only.
>
> >> > +static void mtk_iommu_detach_device(struct iommu_domain *domain,
> >> > + struct device *dev)
> >> > +{
> >>
> >> No hardware (de)configuration or clean-up necessary?
> > I will add it. Actually we design like this:If a device have attached to
> > iommu domain, it won't detach from it.
>
> Isn't proper clean-up required for module removal? Some drivers might
> be required to be loadable modules, which should be unloadable.
>
> >>
> >> > +
> >> > + piommu->protect_va = devm_kmalloc(piommu->dev, MTK_PROTECT_PA_ALIGN*2,
> >>
> >> style: Operators like * should have space on both sides.
> >>
> >> > + GFP_KERNEL);
> >>
> >> Shouldn't dma_alloc_coherent() be used for this?
> > We don't care the data in it. I think they are the same. Could you
> > help tell me why dma_alloc_coherent may be better.
>
> Can you guarantee that at the time you allocate the memory using
> devm_kmalloc() the memory is not dirty (i.e. some write back data are
> stored in CPU cache) and is not going to be written back in some time,
> overwriting data put there by IOMMU hardware?
>
As I noted in the function "mtk_iommu_hw_init":
/* protect memory,HW will write here while translation fault */
protectpa = __virt_to_phys(piommu->protect_va);
We don’t care the content of this buffer, It is ok even though its
data is dirty.
It seem to be a the protect memory. While a translation fault
happened, The iommu HW will overwrite here instead of writing to the
fault physical address which may be 0 or some random address.
> >> > +
> >> > + iommu_set_fault_handler(domain, mtk_iommu_fault_handler, piommu);
> >>
> >> I don't see any other drivers doing this. Isn't this for upper layers,
> >> so that they can set their own generic fault handlers?
> > I think that this function is related with the iommu domain, we
> > have only one multimedia iommu domain. so I add it after the iommu
> > domain are created.
>
> No, this function is for drivers of IOMMU clients (i.e. master IP
> blocks) which want to subscribe to page fault to do things like paging
> on demand and so on. It shouldn't be called by IOMMU driver. Please
> see other IOMMU drivers, for example rockchip-iommmu.c.
Thanks. I have read it. I will delete it and print the error info
in the ISR. Also call the report_iommu_fault in the ISR.
> Best regards,
> Tomasz
next prev parent reply other threads:[~2015-04-14 6:31 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
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 [this message]
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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