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? > Can the kernel allocate the required size automatically? Yes, if you tell it on the kernel command line :). 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. > The vc4 has probably some configuration in devicetree. As I understand > it the devicetree is taken from some place other than the kernel. By default we take the device tree from U-Boot. I have changes in progress that would take them one step higher up from the RPi firmware even, so that changes to config.txt actually get populated into the Linux device tree. > Is this devicetree ever updated after copying the image to the SD card? Yes, it comes from the U-Boot package right now. Alex -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
