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 >
