Hi Nishanth,
Thanks for the review.
On 06/08/23 01:03, Nishanth Menon wrote:
> 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.
Sorry but I did not understand clearly the disadvantage of this approach.
Here we are reserving CMA and also marking it as re-usable so that in case
driver is not using it OS can use that region.
Also I see quite a few vendors already taking this approach :
$grep -r cma-default arch/arm64/boot/dts
arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts:276:
linux,cma-default;
arch/arm64/boot/dts/qcom/sc8280xp-crd.dts:222:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl.dts:201:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8ulp-evk.dts:32:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8-apalis-v1.1.dtsi:198:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8mm-tqma8mqml.dtsi:48:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8dxl-evk.dts:50:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx93-tqma9352.dtsi:24:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8mq-tqma8mq.dtsi:59:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx8mn-tqma8mqnl.dtsi:46:
linux,cma-default;
arch/arm64/boot/dts/freescale/imx93-11x11-evk.dts:28:
linux,cma-default;
arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts:67:
linux,cma-default;
arch/arm64/boot/dts/amlogic/meson-gx.dtsi:63:
linux,cma-default;
arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi:121:
linux,cma-default;
arch/arm64/boot/dts/amlogic/meson-a1.dtsi:59:
linux,cma-default;
I am esp concerned since there are platforms based on
> am62x and just 256MB DDR.
>
The file "k3-am62x-sk-common.dtsi" refers DDR memory size as 2Gb[1] and so I
put CMA reservation in same file assuming all boards including this file have
2Gb.
But if there are some boards having lesser DDR and including this
k3-am62x-sk-common.dtsi and overriding memory node, I can put the CMA
reservation node in board specific file i.e. k3-am625-sk.dts in V2.
Kindly let me know if above is preferred approach.
[1]
https://gitlab.com/linux-kernel/linux-next/-/blob/next-20230807/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi?ref_type=tags#L33
Regards
Devarsh
>> 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
>>
>
