[PATCH v2 xserver 00/11] modesetting: MS_ALL_IN_ONE

[Hans de Goede]

Hi,

On 09-01-17 02:52, Yu, Qiang wrote:
>
> Hi Hans,
>
> I forgot there is another difference, PRIME solution has to copy screen once before display
> to iGPU while MS_ALL_IN_ONE don't have to and can display what full screen app draws
> directly by page flip (for DRI2) which may be important for embedded platforms with week
> GPU and limited memory bandwidths.

Hmm, I guess you're talking imx6 + etnaviv now right, because with a discrete GPU
+ iGPU displaying the rendered frame, we are always going to need one copy from
discrete-GPU RAM to system RAM. But I agree that getting rid of the extra copy for
imx6 would be really good, I even dare to call it a must-have feature.

> Benefit from common interface of drm/gbm/egl, may be modesetting can play a bigger role
> of span multi drm devices to give more optimization like this and:
> 1. multi render node, a single protocol screen to accept request and dispatch to each render
> node for render
> 2. multi display node associate with the render node (some display node has the same drm
> device with render node), so no need to handle bo tile-linear copy and each render node can
> handle request of its related display node.

Ack I agree that we would need to do better here, but I don't believe this should be some
special mode activated by some special means, e.g. in the imx6 + etnaviv case the modesetting
driver should simply recognize that they are sharing RAM and use page-flipping (passing buffer
ownership between the 2) rather then copying, without the user needing to do anything
special.

Regards,

Hans