From: Manivannan Sadhasivam <mani@kernel.org>
To: Chen-Yu Tsai <wenst@chromium.org>
Cc: "Matthias Brugger" <matthias.bgg@gmail.com>,
"AngeloGioacchino Del Regno"
<angelogioacchino.delregno@collabora.com>,
"Ryder Lee" <ryder.lee@mediatek.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Conor Dooley" <conor+dt@kernel.org>,
devicetree@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dt-bindings: PCI: mediatek-gen3: Allow memory-region for restricted DMA buffer
Date: Thu, 14 May 2026 17:18:14 +0530 [thread overview]
Message-ID: <qnikqcqoiw7z2yh5wruqcli3rk56yomyymghzivlcmekp2blwc@dfhsfl3sqcla> (raw)
In-Reply-To: <CAGXv+5GAaMQbaoUVr5zcwtHaofyXwHz03TxBe-QyWj_sNoQZsg@mail.gmail.com>
On Thu, May 14, 2026 at 03:54:29PM +0800, Chen-Yu Tsai wrote:
> On Thu, May 14, 2026 at 1:23 PM Manivannan Sadhasivam <mani@kernel.org> wrote:
> >
> > On Fri, May 08, 2026 at 02:36:32PM +0800, Chen-Yu Tsai wrote:
> > > On some SoCs without an IOMMU behind the PCIe controller, the PCIe
> > > controller memory access could be limited to a small region by the
> > > firmware configuring a memory protection unit. This memory region
> > > must be assigned to the PCIe controller so that the OS knows to
> > > use that region. Otherwise PCIe devices would not work properly.
> > >
> >
> > So this means, the PCIe devices can only access a specific carveout memory
> > configured by MPU for DMA? If so, you should use 'dma-ranges' as suggested by
> > Rob.
> >
> > 'memory-region' also serves the purpose, but for PCI, we have the dedicated
> > 'dma-ranges' property.
>
> I think I need some sort of guide on writing the 'dma-ranges' property,
> because it is not working for me.
>
> I'm adding
>
> dma-ranges = <0x42000000 0 0x00000000 0 0xc0000000 0 0x4000000>;
>
So the device DMA address start from 0x0? Isn't it a 1:1 mapping?
dma-ranges = <0x42000000 0 0xc0000000 0 0xc0000000 0 0x4000000>;
- Mani
--
மணிவண்ணன் சதாசிவம்
next prev parent reply other threads:[~2026-05-14 11:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-08 6:36 [PATCH] dt-bindings: PCI: mediatek-gen3: Allow memory-region for restricted DMA buffer Chen-Yu Tsai
2026-05-08 17:54 ` Bjorn Helgaas
2026-05-11 5:15 ` Chen-Yu Tsai
2026-05-11 10:04 ` AngeloGioacchino Del Regno
2026-05-13 23:15 ` Rob Herring
2026-05-14 8:12 ` Chen-Yu Tsai
2026-05-14 5:23 ` Manivannan Sadhasivam
2026-05-14 7:54 ` Chen-Yu Tsai
2026-05-14 11:48 ` Manivannan Sadhasivam [this message]
2026-05-15 9:16 ` Chen-Yu Tsai
2026-05-15 12:34 ` Manivannan Sadhasivam
2026-05-18 9:02 ` Chen-Yu Tsai
2026-05-19 7:21 ` Manivannan Sadhasivam
2026-05-19 8:42 ` Chen-Yu Tsai
2026-06-01 21:48 ` Rob Herring
2026-06-02 7:02 ` Chen-Yu Tsai
2026-06-09 3:33 ` Chen-Yu Tsai
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