linux-kernel - Re: [PATCH 1/3] arm64: dts: qcom: sc7280: Increase config size to 256MB for ECAM feature

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Message-ID: <20241205164224.GA3053577@bhelgaas>
Date: Thu, 5 Dec 2024 10:42:24 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Krishna chaitanya chundru <quic_krichai@...cinc.com>,
	cros-qcom-dts-watchers@...omium.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, quic_vbadigan@...cinc.com,
	quic_ramkri@...cinc.com, quic_nitegupt@...cinc.com,
	quic_skananth@...cinc.com, quic_vpernami@...cinc.com,
	quic_mrana@...cinc.com, mmareddy@...cinc.com,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 1/3] arm64: dts: qcom: sc7280: Increase config size to
 256MB for ECAM feature

On Thu, Dec 05, 2024 at 05:11:25PM +0100, Konrad Dybcio wrote:
> On 16.11.2024 11:00 PM, Krishna chaitanya chundru wrote:
> > Increase the configuration size to 256MB as required by the ECAM feature.
> > And also move config space, DBI, ELBI, IATU to upper PCIe region and use
> > lower PCIe region entierly for BAR region.
> > 
> > Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> > ---
> >  arch/arm64/boot/dts/qcom/sc7280.dtsi | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > index 3d8410683402..a7e3d3e9d034 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > @@ -2196,10 +2196,10 @@ wifi: wifi@...10040 {
> >  		pcie1: pcie@...8000 {
> >  			compatible = "qcom,pcie-sc7280";
> >  			reg = <0 0x01c08000 0 0x3000>,
> > -			      <0 0x40000000 0 0xf1d>,
> > -			      <0 0x40000f20 0 0xa8>,
> > -			      <0 0x40001000 0 0x1000>,
> > -			      <0 0x40100000 0 0x100000>;
> > +			      <4 0x00000000 0 0xf1d>,
> > +			      <4 0x00000f20 0 0xa8>,
> > +			      <4 0x10000000 0 0x1000>,
> > +			      <4 0x00000000 0 0x10000000>;
> 
> So this region is far bigger, any reason to use 256MiB specifically?

I assume this is because ECAM takes 1MB/bus, and pcie1 has
bus-range = <0x00 0xff>.  If one wanted a smaller ECAM area,
I assume one would limit bus-range to match.

Bjorn