linux-kernel - Re: [PATCH v10 15/15] arm64: dts: qcom: sa8775p: add a dedicated memory carveout for TZ

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Date: Wed, 29 May 2024 16:39:28 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Robert Marko <robimarko@...il.com>, Das Srinagesh <quic_gurus@...cinc.com>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Maximilian Luz <luzmaximilian@...il.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Srini Kandagatla <srinivas.kandagatla@...aro.org>, Arnd Bergmann <arnd@...db.de>, 
	Elliot Berman <quic_eberman@...cinc.com>, Alex Elder <elder@...nel.org>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kernel@...cinc.com
Subject: Re: [PATCH v10 15/15] arm64: dts: qcom: sa8775p: add a dedicated
 memory carveout for TZ

On Wed, May 29, 2024 at 4:26 PM Konrad Dybcio <konrad.dybcio@...aroorg> wrote:
>
> On 27.05.2024 2:55 PM, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > Add a 20MB reserved memory region for use by SCM calls.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/sa8775p.dtsi | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sa8775p.dtsi b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> > index 31de73594839..c183527452d7 100644
> > --- a/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> > @@ -208,6 +208,7 @@ core3 {
> >       firmware {
> >               scm {
> >                       compatible = "qcom,scm-sa8775p", "qcom,scm";
> > +                     memory-region = <&tz_ffi_mem>;
> >               };
> >       };
> >
> > @@ -418,6 +419,12 @@ cdt_data_backup_mem: cdt-data-backup@...a0000 {
> >                       no-map;
> >               };
> >
> > +             tz_ffi_mem: tz-ffi@...00000 {
> > +                     compatible = "shared-dma-pool";
> > +                     reg = <0x0 0x91c00000 0x0 0x1400000>;
>
> How does that size relate to
>
> +       pool_config.max_size = SZ_256K;
>
> in patch 3?
>
> Konrad

Short answer: it doesn't.

Slightly less short answer: this is the limit of *this* specific TZMem
pool which in turn gets its memory from the shared DMA pool. We can
have multiple TZMem pools and they all share this DMA pool.

Bartosz