On Mon, 25 Dec 2017 22:18:45 +0100 Alexander Graf <[email protected]> wrote:
> On 25.12.17 18:36, Michal Suchánek wrote: > > Hello, > > > > for testing I installed stable and master kernel on Leap 42.3 E20 > > image. > > > > Initially it would work fine but later I would have to add cma=256MB > > (some random value found on a forum) to kernel commandline for video > > output to work. > > > > Has the cma requirement changed as a result of recent vc4 changes? > > No, it's always been there. In the early days we had a default CMA > size of 64MB IIRC, but given that a good number of platforms don't > need any CMA space at all, it seemed like a wasted allocation. > > For the RPi, we added a CMA command line parameter to the kiwi file to > override the default 0MB allocation. Maybe something went wrong and > that change never happened in Leap 42.3? Maybe 42.3 dose not really need it because it does not have the driver in the kernel or still has the 64MB default. > > > Can the kernel allocate the required size automatically? > > Yes, if you tell it on the kernel command line :). I do not have to tell the kernel I have an integrated Intel graphics card and it can still allocate its buffers just fine. > Really, CMA is all > about reserving a range of memory space for contiguous allocations, so > all allocations happening inside that range have to be movable and can > be forced to move at any given point in time. > > I'm not quite sure what the kernel should do more automatically than > it already does. Just allocate the buffer whenever there is a vc4 card :) Thanks Michal -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
