Heiko, On Thu, Aug 6, 2015 at 10:33 AM, Heiko St?bner <heiko at sntech.de> wrote: > The all current Rockchip SoCs supporting 4GB of ram have problems accessing > the memory region 0xfe000000~0xff000000. This also seems to includes the > rk3368 arm64 soc. > > All current code handling dma memory oddities I could find, seem to involve > soc-specific code (zone-dma or so) while this issue is shared between arm32 > and arm64 socs from Rockchip, which would need to have this described in > the soc devicetree on both socs. > > Limiting the dma-zone alone also does not solve the issue and as the > dma-masks need to be a power-of-two in the kernel, the next lower dma-mask > brings memory usable for dma down to 2GB. > > So as a stop-gap block off the affected region to prevent its use by > devices with 4GB of memory, like some recent Chromebooks. > > Signed-off-by: Heiko Stuebner <heiko at sntech.de> > --- > changes since v1: > - expand reasons for the reserved memory > > arch/arm/boot/dts/rk3288.dtsi | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) As discussed earlier, I'm now convinced that this is an appropriate stopgap. ...and the description looks good to me. Reviewed-by: Douglas Anderson <dianders at chromium.org>
