From: Chen-Yu Tsai <wenst@chromium.org>
To: Rob Herring <robh@kernel.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>,
"Manivannan Sadhasivam" <mani@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 16:12:28 +0800 [thread overview]
Message-ID: <CAGXv+5EXw4rXD7URhXvotxsPG81EGhhk6wqnFuVWig=dTdNCXA@mail.gmail.com> (raw)
In-Reply-To: <20260513231550.GA2280946-robh@kernel.org>
On Thu, May 14, 2026 at 7:15 AM Rob Herring <robh@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.
> >
>
> What you are describing is dma-ranges. Why not use that?
Answer from yesterday:
I didn't know about it. I was just moving the property from the WiFi
controller node down to the PCIe controller in the other DT patch [1].
Answer from today:
Also, it doesn't work. See my reply to Mani.
ChenYu
> > Allow the memory-region property with one item pointing to a
> > restricted DMA buffer.
> >
> > Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> > ---
> > This patch compliments another patch that moved the memory-region from
> > the PCIe device to the PCIe controller [1].
> >
> > [1] https://lore.kernel.org/all/20260430120725.241779-1-wenst@chromium.org/
> >
> > Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml b/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
> > index 4db700fc36ba..4a9e41d01628 100644
> > --- a/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
> > +++ b/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
> > @@ -115,6 +115,10 @@ properties:
> > power-domains:
> > maxItems: 1
> >
> > + memory-region:
> > + maxItems: 1
> > + description: phandle to restricted DMA buffer
> > +
> > mediatek,pbus-csr:
> > $ref: /schemas/types.yaml#/definitions/phandle-array
> > items:
> > --
> > 2.54.0.563.g4f69b47b94-goog
> >
next prev parent reply other threads:[~2026-05-14 8:12 UTC|newest]
Thread overview: 18+ 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 [this message]
2026-05-14 5:23 ` Manivannan Sadhasivam
2026-05-14 7:54 ` Chen-Yu Tsai
2026-05-14 11:48 ` Manivannan Sadhasivam
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
2026-06-12 14:32 ` Rob Herring (Arm)
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