From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Jianjun Wang <jianjun.wang@mediatek.com>
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
ryder.lee@mediatek.com, linux-pci@vger.kernel.org,
youlin.pei@mediatek.com, linux-kernel@vger.kernel.org,
robh+dt@kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
honghui.zhang@mediatek.com, matthias.bgg@gmail.com,
linux-mediatek@lists.infradead.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] PCI: mediatek: Add controller support for MT7629
Date: Tue, 18 Dec 2018 15:32:32 +0000 [thread overview]
Message-ID: <20181218153232.GA6715@e107981-ln.cambridge.arm.com> (raw)
In-Reply-To: <1545124764.25199.3.camel@mhfsdcap03>
On Tue, Dec 18, 2018 at 05:19:24PM +0800, Jianjun Wang wrote:
> On Mon, 2018-12-17 at 15:46 +0000, Lorenzo Pieralisi wrote:
> > On Mon, Dec 17, 2018 at 08:32:47AM -0600, Bjorn Helgaas wrote:
> > > On Mon, Dec 17, 2018 at 04:19:39PM +0800, Jianjun Wang wrote:
> > > > On Thu, 2018-12-13 at 08:55 -0600, Bjorn Helgaas wrote:
> > > > > On Thu, Dec 06, 2018 at 09:09:13AM +0800, Jianjun Wang wrote:
> > > > > > The read value of BAR0 is 0xffff_ffff, it's size will be calculated as 4GB
> > > > > > in arm64 but bogus alignment values at arm32, the pcie device and devices
> > > > > > behind this bridge will not be enabled. Fix it's BAR0 resource size to
> > > > > > guarantee the pcie devices will be enabled correctly.
> > > > >
> > > > > So this is a hardware erratum? Per spec, a memory BAR has bit 0 hardwired
> > > > > to 0, and an IO BAR has bit 1 hardwired to 0.
> > > >
> > > > Yes, it only works properly on 64bit platform.
> > >
> > > I don't understand. BARs are supposed to work the same regardless of
> > > whether it's a 32- or 64-bit platform. If this is a workaround for a
> > > hardware defect, please just say that explicitly.
> >
> > I do not understand this either. First thing to do is to describe the
> > problem properly so that we can actually find a solution to it.
> >
> > Lorenzo
>
> This BAR0 is a 64-bit memory BAR, the HW default values for this BAR is
> 0xffff_ffff_0000_0000 and it could not be changed except by config write
> operation.
>
> The calculated BAR size will be 0 in 32-bit platform since the
> phys_addr_t is a 32bit value in 32-bit platform.
>
> Actually MediaTek's HW does not using this BAR0, just omit it when
> assign resource is totally fine.
>
> When assign the resource for each device, software will check the
> resource alignment first, and the resource of length zero will be
> regarded as a bogus alignment resource, it will be ignored and won't
> claim a resource parent for it.
>
> When drivers try to enable the PCIe devices, the software will enable
> it's resources, but it will return an error number when found a
> unclaimed resource, in that case, the flow of enable devices will be
> interrupted and PCIe devices won't work properly.
As a starting point, please provide kernel logs for both 64-bit and
32-bit platforms (without this patch applied) and also a:
cat /proc/iomem
and
lspci
output for both configurations.
Thanks,
Lorenzo
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next prev parent reply other threads:[~2018-12-18 15:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-06 1:09 [PATCH 0/2] PCI: mediatek: Add support for MT7629 Jianjun Wang
2018-12-06 1:09 ` [PATCH 1/2] dt-bindings: PCI: " Jianjun Wang
2018-12-19 20:38 ` Rob Herring
2018-12-06 1:09 ` [PATCH 2/2] PCI: mediatek: Add controller " Jianjun Wang
2018-12-06 5:53 ` Honghui Zhang
2018-12-07 12:56 ` Jianjun Wang
2018-12-12 5:43 ` Honghui Zhang
2018-12-13 3:39 ` Ryder Lee
2018-12-17 7:51 ` Jianjun Wang
2018-12-13 14:55 ` Bjorn Helgaas
2018-12-17 8:19 ` Jianjun Wang
2018-12-17 14:32 ` Bjorn Helgaas
2018-12-17 15:46 ` Lorenzo Pieralisi
2018-12-18 9:19 ` Jianjun Wang
2018-12-18 15:32 ` Lorenzo Pieralisi [this message]
2018-12-21 13:13 ` Jianjun Wang
2018-12-20 18:20 ` Bjorn Helgaas
2018-12-24 11:40 ` Jianjun Wang
2019-01-23 15:40 ` Lorenzo Pieralisi
2019-02-19 7:01 ` Jianjun Wang
2019-02-19 15:03 ` Lorenzo Pieralisi
2019-06-28 6:38 ` Jianjun Wang
2018-12-06 1:40 ` [PATCH 0/2] PCI: mediatek: Add " Ryder Lee
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