Re: [PATCH v2 4/6] arm64: dts: ti: k3-j784s4-j742s2-main-common: Assign SRAM to VPU nodes

[Brandon Brnich]

Hi Udit,

On 9/5/26 7:48 AM, Kumar, Udit wrote:
> On 8/11/2026 2:22 AM, Brandon Brnich wrote:
> > The Wave5 VPU supports connecting to on-chip SRAM through its secondary
> > AXI interface. This allows temporal buffers to be stored on a per-stream
> > basis, reducing DDR memory traffic.
> >
> > Signed-off-by: Brandon Brnich <b-brnich@xxxxxx>
> > Reviewed-by: Andrew Davis <afd@xxxxxx>
> > ---
> >   arch/arm64/boot/dts/ti/k3-j784s4-j742s2-main-common.dtsi | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-main-common.dtsi b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-main-common.dtsi
> > index e836f0f42e30d..21ec9f207ff63 100644
> > --- a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-main-common.dtsi
> > +++ b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-main-common.dtsi
> > @@ -1002,6 +1002,7 @@ vpu0: video-codec@4210000 {
> >   		interrupts = <GIC_SPI 182 IRQ_TYPE_LEVEL_HIGH>;
> >   		clocks = <&k3_clks 241 2>;
> >   		power-domains = <&k3_pds 241 TI_SCI_PD_EXCLUSIVE>;
> > +		sram = <&main_navss_sram>;
> >   	};
> >   
> >   	vpu1: video-codec@4220000 {
> > @@ -1010,6 +1011,7 @@ vpu1: video-codec@4220000 {
> >   		interrupts = <GIC_SPI 183 IRQ_TYPE_LEVEL_HIGH>;
> >   		clocks = <&k3_clks 242 2>;
> >   		power-domains = <&k3_pds 242 TI_SCI_PD_EXCLUSIVE>;
> > +		sram = <&main_navss_sram>;
> >   	};
>
> Hello Brandon,
> Could you check, how two instances of hardware can share same sram ?

If both instances are used in parallel, then only 1 would get the 
benefits of b/w savings with this current patch. These VPU instances are 
in a race to see who gets the pool depending on which instance allocates 
the first stream. Current Wave5 driver will take the entire 64 KB pool 
once a stream is opened. The pool is not released until all associated 
streams with that instance are freed.

I will look to see if the driver can be modified at all here. If it 
can't, then I will find another node of available SRAM that I can hook 
up to 2nd instance. For now, we can drop this patch and associated patch 
adding main_navss_sram to J784s4 in this series.

Best,
Brandon

> LTM, each block need 64KB of SRAM
> https://elixir.bootlin.com/linux/v7.2.2/source/drivers/media/platform/chips-media/wave5/wave5-vpu.c#L463>
>
> >   
> >   	main_sdhci0: mmc@4f80000 {