From: Bjorn Helgaas <helgaas@kernel.org>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: "Serge Semin" <Sergey.Semin@baikalelectronics.ru>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
"Jingoo Han" <jingoohan1@gmail.com>,
"Gustavo Pimentel" <gustavo.pimentel@synopsys.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Alexey Malahov" <Alexey.Malahov@baikalelectronics.ru>,
"Pavel Parkhomenko" <Pavel.Parkhomenko@baikalelectronics.ru>,
"Frank Li" <Frank.Li@nxp.com>,
"Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
"Rob Herring" <robh+dt@kernel.org>,
linux-pci@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND v4 15/15] PCI: dwc: Introduce dma-ranges property support for RC-host
Date: Fri, 29 Jul 2022 06:33:45 -0500 [thread overview]
Message-ID: <20220729113345.GA445581@bhelgaas> (raw)
In-Reply-To: <20220729045220.akdabli5szd5lbdt@mobilestation>
On Fri, Jul 29, 2022 at 07:52:20AM +0300, Serge Semin wrote:
> On Thu, Jul 28, 2022 at 05:11:20PM -0500, Bjorn Helgaas wrote:
> > On Fri, Jun 24, 2022 at 05:39:47PM +0300, Serge Semin wrote:
> > > In accordance with the generic PCIe Root Port DT-bindings the "dma-ranges"
> > > property has the same format as the "ranges" property. The only difference
> > > is in their semantics. The "dma-ranges" property describes the PCIe-to-CPU
> > > memory mapping in opposite to the CPU-to-PCIe mapping of the "ranges"
> > > property. Even though the DW PCIe controllers are normally equipped with
> > > the internal Address Translation Unit which inbound and outbound tables
> > > can be used to implement both properties semantics, it was surprising for
> > > me to discover that the host-related part of the DW PCIe driver currently
> > > supports the "ranges" property only while the "dma-ranges" windows are
> > > just ignored. Having the "dma-ranges" supported in the driver would be
> > > very handy for the platforms, that don't tolerate the 1:1 CPU-PCIe memory
> > > mapping and require a customized PCIe memory layout. So let's fix that by
> > > introducing the "dma-ranges" property support.
>
> > Do we have a platform that requires this yet? Or does this fix a bug?
> >
> > I see that dw_pcie_host_init() calls devm_pci_alloc_host_bridge(),
> > which eventually parses "dma-ranges", but I don't see any DWC DT
> > bindings that use it yet.
> >
> > I'm not clear on what value this adds today.
>
> There are several points of having this supported.
> First of all, generic PCIe DT-bindings permit having the dma-ranges
> specified for the PCIe RCs. If so having it unsupported by the driver
> just breaks the bindings or at least makes it incomplete.
Are there bindings in the tree that are broken and will be fixed by
this?
> Second, the main point of this patchset is to add the dma-ranges
> support.) Especially seeing some other PCIe RC drivers do have it
> supported too.
> Finally. It is required for our platform (and for all the platforms
> with similar issues). The problem is that the outbound source window
> base address (on CPU-side) is size-unaligned. It resides at the 128MB
> base address (size is somewhat about ~335MB). In case of the
> one-on-one CPU->PCI mapping the peripherals with relatively big BARs
> (at least of 256MB) and which need the BARs having size-aligned memory
> won't be supported. So we had to remap the PCIe space to the
> size-aligned base address. But in its turn that caused the PCIe-CPU
> memory overlap. So PCIe DMA stopped working for the overlapped memory
> due to the implicit P2P transactions. In order to fix that we had to
> add the dma-ranges support to the DW PCIe driver and use it to remap
> the overlapped memory. So please add this patch to the repo. We really
> need it.
Does the above apply to the pending Baikal-T1 driver? If so, let's
just include this patch in that series. Then we'll have a user of
this functionality and we'll be able to exercise and test this code.
Bjorn
next prev parent reply other threads:[~2022-07-29 11:33 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-24 14:39 [PATCH RESEND v4 00/15] PCI: dwc: Add hw version and dma-ranges support Serge Semin
2022-06-24 14:39 ` [PATCH RESEND v4 01/15] PCI: dwc: Add more verbose link-up message Serge Semin
2022-08-01 12:59 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 02/15] PCI: dwc: Detect iATU settings after getting "addr_space" resource Serge Semin
2022-07-28 14:38 ` Bjorn Helgaas
2022-08-01 13:01 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 03/15] PCI: dwc: Convert to using native IP-core versions representation Serge Semin
2022-07-28 15:24 ` Bjorn Helgaas
2022-07-28 15:31 ` Ben Dooks
2022-07-28 16:34 ` Bjorn Helgaas
2022-07-28 18:53 ` Serge Semin
2022-08-01 13:07 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 04/15] PCI: dwc: Add IP-core version detection procedure Serge Semin
2022-08-01 13:12 ` Manivannan Sadhasivam
2022-08-01 20:06 ` Bjorn Helgaas
2022-08-02 7:31 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 05/15] PCI: dwc: Introduce Synopsys IP-core versions/types interface Serge Semin
2022-08-01 13:21 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 06/15] PCI: intel-gw: Drop manual DW PCIe controller version setup Serge Semin
2022-08-01 13:28 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 07/15] PCI: tegra194: " Serge Semin
2022-06-27 7:59 ` Vidya Sagar
2022-06-27 22:31 ` Serge Semin
2022-08-01 13:29 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 08/15] PCI: dwc: Add host de-initialization callback Serge Semin
2022-08-01 13:33 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 09/15] PCI: dwc: Drop inbound iATU types enumeration - dw_pcie_as_type Serge Semin
2022-08-01 13:36 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 10/15] PCI: dwc: Drop iATU regions enumeration - dw_pcie_region_type Serge Semin
2022-08-01 13:37 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 11/15] PCI: dwc: Simplify in/outbound iATU setup methods Serge Semin
2022-08-01 13:50 ` Manivannan Sadhasivam
2022-08-01 20:11 ` Bjorn Helgaas
2022-06-24 14:39 ` [PATCH RESEND v4 12/15] PCI: dwc: Add iATU regions size detection procedure Serge Semin
2022-08-01 13:52 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 13/15] PCI: dwc: Verify in/out regions against iATU constraints Serge Semin
2022-08-01 13:53 ` Manivannan Sadhasivam
2022-06-24 14:39 ` [PATCH RESEND v4 14/15] PCI: dwc: Check iATU in/outbound ranges setup methods status Serge Semin
2022-08-01 13:54 ` Manivannan Sadhasivam
2022-08-01 20:17 ` Bjorn Helgaas
2022-06-24 14:39 ` [PATCH RESEND v4 15/15] PCI: dwc: Introduce dma-ranges property support for RC-host Serge Semin
2022-07-28 22:11 ` Bjorn Helgaas
2022-07-29 4:52 ` Serge Semin
2022-07-29 11:33 ` Bjorn Helgaas [this message]
2022-07-29 14:38 ` Serge Semin
2022-08-01 14:00 ` Manivannan Sadhasivam
2022-08-09 20:07 ` Serge Semin
2022-07-11 18:48 ` [PATCH RESEND v4 00/15] PCI: dwc: Add hw version and dma-ranges support Serge Semin
2022-07-27 22:49 ` Bjorn Helgaas
2022-07-28 12:21 ` Serge Semin
2022-07-29 2:36 ` Bjorn Helgaas
2022-09-28 8:10 ` Lorenzo Pieralisi
2022-09-28 10:53 ` Serge Semin
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