On 16:44-20230803, Devarsh Thakkar wrote:
> Reserve 128MiB of global CMA which is also marked as re-usable
> so that OS can also use the same if peripheral drivers are not using the
> same.
>
> AM62x supports multimedia components such as GPU, dual Display and Camera.
> Assuming the worst-case scenario where all 3 are run in parallel below
> is the calculation :
>
> 1) OV5640 camera sensor supports 1920x1080 resolution
> -> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers
> (default in yavta) : 32MiB
>
> 2) 1920x1200 Microtips LVDS panel supported
> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers :
> 16 MiB
>
> 3) 1920x1080 HDMI display supported
> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers :
> 15.82 MiB which is ~16 MiB
>
> 4) IMG GPU shares with display allocated buffers while rendering
> but in case some dedicated operation viz color conversion,
> keeping same window of ~16 MiB for GPU too.
>
> Total is 80 MiB and adding 32 MiB for other peripherals and extra
> 16 MiB to keep as buffer for fragmentation thus rounding total to 128
> MiB.
>
> Signed-off-by: Devarsh Thakkar <devarsht@xxxxxx>
> Acked-by: Darren Etheridge <detheridge@xxxxxx>
> Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
> ---
I don't think this is right approach. There are other techniques
than having to do this (Andrew: please comment) and require drivers to
behave properly. I am esp concerned since there are platforms based on
am62x and just 256MB DDR.
> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> index 34c8ffc553ec..9dd6e23ca9ca 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> @@ -47,6 +47,14 @@ ramoops@9ca00000 {
> pmsg-size = <0x8000>;
> };
>
> + /* global cma region */
> + linux,cma {
> + compatible = "shared-dma-pool";
> + reusable;
> + size = <0x00 0x8000000>;
> + linux,cma-default;
> + };
> +
> secure_tfa_ddr: tfa@9e780000 {
> reg = <0x00 0x9e780000 0x00 0x80000>;
> alignment = <0x1000>;
> --
> 2.34.1
>
--
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D
