On Sun, Feb 17, 2019 at 1:07 AM Yong Wu <yong.wu@xxxxxxxxxxxx> wrote: > > MediaTek extend the arm v7s descriptor to support the dram over 4GB. > > In the mt2712 and mt8173, it's called "4GB mode", the physical address > is from 0x4000_0000 to 0x1_3fff_ffff, but from EMI point of view, it > is remapped to high address from 0x1_0000_0000 to 0x1_ffff_ffff, the > bit32 is always enabled. thus, in the M4U, we always enable the bit9 > for all PTEs which means to enable bit32 of physical address. > > but in mt8183, M4U support the dram from 0x4000_0000 to 0x3_ffff_ffff > which isn't remaped. We extend the PTEs: the bit9 represent bit32 of > PA and the bit4 represent bit33 of PA. Meanwhile the iova still is > 32bits. > > In order to unify code, in the "4GB mode", we add the bit32 for the > physical address manually in our driver. > > Correspondingly, Adding bit32 and bit33 for the PA in the iova_to_phys > has to been moved into v7s. > > Regarding whether the pagetable address could be over 4GB, the mt8183 > support it while the previous mt8173 don't. thus keep it as is. > > Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx> > Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx> > --- > Comparing the previous version, I add MTK_4GB quirk always since mtk_iommu > has already controlled the PA itself. Helped from Evan. Thanks for all the explanation on this one. I think I understand it now, and it looks good to me. Reviewed-by: Evan Green <evgreen@xxxxxxxxxxxx>
