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

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Date:   Tue, 9 Jun 2020 23:58:05 +0800
From:   dillon min <dillon.minfei@...il.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux@...linux.org.uk, Vladimir Murzin <vladimir.murzin@....com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        allison@...utok.net, info@...ux.net, tglx@...utronix.de, hch@....de
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] Use 'arm_nommu_dma_ops' to handle dma memroy if
 device offer consistent dma memory region

Hi Christoph Hellwig,

This is the patchset. for your reference.

thanks,

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