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

[dillon min]

Hi Christoph Hellwig,

This is the patchset. for your reference.

thanks,

On Mon, Jun 8, 2020 at 4:30 PM <dillon.minfei@xxxxxxxxx> wrote:
>
> From: dillon min <dillon.minfei@xxxxxxxxx>
>
> 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(-)
>
> --
> 2.7.4
>