On 09/09/2019 21:33, Stefan Wahren wrote: > Hi Nicolas, > > Am 09.09.19 um 11:58 schrieb Nicolas Saenz Julienne: >> Hi all, >> this series attempts to address some issues we found while bringing up >> the new Raspberry Pi 4 in arm64 and it's intended to serve as a follow >> up of these discussions: >> v4: https://lkml.org/lkml/2019/9/6/352 >> v3: https://lkml.org/lkml/2019/9/2/589 >> v2: https://lkml.org/lkml/2019/8/20/767 >> v1: https://lkml.org/lkml/2019/7/31/922 >> RFC: https://lkml.org/lkml/2019/7/17/476 >> >> The new Raspberry Pi 4 has up to 4GB of memory but most peripherals can >> only address the first GB: their DMA address range is >> 0xc0000000-0xfc000000 which is aliased to the first GB of physical >> memory 0x00000000-0x3c000000. Note that only some peripherals have these >> limitations: the PCIe, V3D, GENET, and 40-bit DMA channels have a wider >> view of the address space by virtue of being hooked up trough a second >> interconnect. >> >> Part of this is solved on arm32 by setting up the machine specific >> '.dma_zone_size = SZ_1G', which takes care of reserving the coherent >> memory area at the right spot. That said no buffer bouncing (needed for >> dma streaming) is available at the moment, but that's a story for >> another series. >> >> Unfortunately there is no such thing as 'dma_zone_size' in arm64. Only >> ZONE_DMA32 is created which is interpreted by dma-direct and the arm64 >> arch code as if all peripherals where be able to address the first 4GB >> of memory. >> >> In the light of this, the series implements the following changes: >> >> - Create both DMA zones in arm64, ZONE_DMA will contain the first 1G >> area and ZONE_DMA32 the rest of the 32 bit addressable memory. So far >> the RPi4 is the only arm64 device with such DMA addressing limitations >> so this hardcoded solution was deemed preferable. >> >> - Properly set ARCH_ZONE_DMA_BITS. >> >> - Reserve the CMA area in a place suitable for all peripherals. >> >> This series has been tested on multiple devices both by checking the >> zones setup matches the expectations and by double-checking physical >> addresses on pages allocated on the three relevant areas GFP_DMA, >> GFP_DMA32, GFP_KERNEL: >> >> - On an RPi4 with variations on the ram memory size. But also forcing >> the situation where all three memory zones are nonempty by setting a 3G >> ZONE_DMA32 ceiling on a 4G setup. Both with and without NUMA support. >> > i like to test this series on Raspberry Pi 4 and i have some questions > to get arm64 running: > > Do you use U-Boot? Which tree? If you want to use U-Boot, try v2019.10-rc4, it should have everything you need to boot your kernel. Regards, Matthias > Are there any config.txt tweaks necessary? > >
