On Thu, 28 Dec 2017 16:35:51 +0100 Andreas Färber <[email protected]> wrote:
> Am 28.12.2017 um 16:29 schrieb Michal Suchánek: > > On Mon, 25 Dec 2017 22:18:45 +0100 > > Alexander Graf <[email protected]> wrote: > >> On 25.12.17 18:36, Michal Suchánek wrote: > >> > >>> 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 :) > > The RPi does not have an IOMMU, so it needs to pre-allocate a > contiguous hunk of memory, unlike other Intel or Arm based systems. AFAIK the iommu feature on Intel has the marketing name VT-d and there are many Intel systems with perfectly working integrated graphics that don't support VT-d. Also the Intel boards with integraded graphics tend to have a BIOS setting for something like "memory reserved for on-board graphics" and the IGP is not enabled unless some memory is allocated for it. On RPi3 the memory map is fabricated somewhere between u-boot and Linux kernel so is completely under control. Which is of course the excuse to not allocate the IGP buffer and leave that to user configureation. The wonders of fully opensource implementation. It's so customizable that it's even unthinkable to suply a working default :-> So yes, I insist that the buffer for the IGP is allocated even in the case there is no proprietary BIOS and there is only opensource software involved in defining the memory map. Is that too much to ask? Thanks Michal -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
