I realized this morning after reading Ard's patch fixing the same issue
in ACPI that we can move the zone_dma_bits initialization later in the
init process. This permits the use of OF to parse dma-ranges in the
system. Something we though we couldn't do on previous iterations of
this.

The series sits on top of Ard's patch "arm64: mm: set ZONE_DMA size
based on early IORT scan."

--- Original cover letter

Using two distinct DMA zones turned out to be problematic. Here's an
attempt go back to a saner default.

I tested this on both a RPi4 and QEMU.

---

Changes since v1:
 - Parse dma-ranges instead of using machine compatible string

Nicolas Saenz Julienne (5):
  arm64: mm: Move zone_dma_bits initialization into zone_sizes_init()
  of/address: Introduce of_dma_lower_bus_limit()
  dma-direct: Turn zone_dma_bits default value into a define
  arm64: mm: Dynamically resize zone_dma_bits based on system's
    constraints
  mm: Update DMA zones description

 arch/arm64/include/asm/processor.h |  1 +
 arch/arm64/mm/init.c               | 12 ++++-------
 drivers/of/address.c               | 34 ++++++++++++++++++++++++++++++
 include/linux/dma-direct.h         |  3 +++
 include/linux/mmzone.h             |  5 +++--
 include/linux/of.h                 |  7 ++++++
 kernel/dma/direct.c                |  2 +-
 7 files changed, 53 insertions(+), 11 deletions(-)

-- 
2.28.0