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[0/2] Use 'arm_nommu_dma_ops' to handle dma memroy if device offer consistent dma memory region

Message ID 1591605038-8682-1-git-send-email-dillon.minfei@gmail.com
Headers show
Series Use 'arm_nommu_dma_ops' to handle dma memroy if device offer consistent dma memory region | expand

Message

Dillon Min June 8, 2020, 8:30 a.m. UTC 
From: dillon min <dillon.minfei@gmail.com>

when do mmap on /dev/fb0, we will get -6 error on cortex-m3/m4 or armv7m
platform without cache support, this is caused by following reason:

on armv7m platform, if no cache support, we will use dma direct mapping,
but, this is not support on !MMU hardware, just return '-ENXIO' error

so, add use_reserved_mem() for these armv7m hardware but no-cache support.
eg, stm32f429/stm32f469.

verified on stm32f469-disco board, mmap frambuffer to userspace.

dillon min (2):
  ARM: dts: stm32: Setup 4M bytes reserved memory for mmap
  arm-nommu: Add use_reserved_mem() to check if device support reserved
    memory

 arch/arm/boot/dts/stm32f469-disco.dts | 14 ++++++++++++++
 arch/arm/mm/dma-mapping-nommu.c       | 28 +++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)