[PATCH v2 0/5] arm64: Default to 32-bit wide ZONE_DMA

[PATCH v2 0/5] arm64: Default to 32-bit wide ZONE_DMA

[Nicolas Saenz Julienne]

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

[PATCH v2 5/5] mm: Update DMA zones description

[Nicolas Saenz Julienne]

The default behavior for arm64 changed, so reflect that.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
---
 include/linux/mmzone.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index fb3bf696c05e..4ee2306351b9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -363,8 +363,9 @@ enum zone_type {
 	 *  - arm only uses ZONE_DMA, the size, up to 4G, may vary depending on
 	 *    the specific device.
 	 *
-	 *  - arm64 has a fixed 1G ZONE_DMA and ZONE_DMA32 for the rest of the
-	 *    lower 4G.
+	 *  - arm64 uses a single 4GB ZONE_DMA, except on the Raspberry Pi 4,
+	 *    in which ZONE_DMA covers the first GB and ZONE_DMA32 the rest of
+	 *    the lower 4GB.
 	 *
 	 *  - powerpc only uses ZONE_DMA, the size, up to 2G, may vary
 	 *    depending on the specific device.
-- 
2.28.0