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From:   dillon min <dillon.minfei@gmail.com>
Date:   Fri, 12 Jun 2020 10:15:08 +0800
Message-ID: <CAL9mu0+ZfW-DoO-DvhvGO-KeGMA+vuHga3FOxN_Ce7uStGPoqg@mail.gmail.com>
Subject: Re: [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device
 support reserved memory
To:     Vladimir Murzin <vladimir.murzin@arm.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Alexandre Torgue <alexandre.torgue@st.com>, info@metux.net,
        linux@armlinux.org.uk,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        tglx@linutronix.de, linux-stm32@st-md-mailman.stormreply.com,
        allison@lohutok.net
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On Thu, Jun 11, 2020 at 11:45 PM Vladimir Murzin
<vladimir.murzin@arm.com> wrote:
>
> On 6/10/20 9:19 AM, Vladimir Murzin wrote:
> > On 6/10/20 8:24 AM, Christoph Hellwig wrote:
> >> Ok, I finally found the original patch from Vladimir.  Comments below:
> >>
> >>> +++ b/kernel/dma/direct.c
> >>> @@ -456,14 +456,14 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
> >>>  #else /* CONFIG_MMU */
> >>>  bool dma_direct_can_mmap(struct device *dev)
> >>>  {
> >>> -   return false;
> >>> +   return true;
> >>>  }
> >>>
> >>>  int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
> >>>             void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >>>             unsigned long attrs)
> >>>  {
> >>> -   return -ENXIO;
> >>> +   return vm_iomap_memory(vma, vma->vm_start, (vma->vm_end - vma->vm_start));;
> >>
> >> I think we should try to reuse the mmu dma_direct_mmap implementation,
> >> which does about the same.  This version has been compile tested on
> >> arm-nommu only, let me know what you think: (btw, a nommu_defconfig of
> >> some kind for arm would be nice..)
> >
> > Catch-all nommu_defconfig is not easy for ARM, AFAIK folk carry few hacks
> > for randconfig...
> >
> > Meanwhile, known working NOMMU configs
> >
> > $ git grep "# CONFIG_MMU is not set" arch/arm/configs/
> > arch/arm/configs/efm32_defconfig:# CONFIG_MMU is not set
> > arch/arm/configs/lpc18xx_defconfig:# CONFIG_MMU is not set
> > arch/arm/configs/mps2_defconfig:# CONFIG_MMU is not set
> > arch/arm/configs/stm32_defconfig:# CONFIG_MMU is not set
> > arch/arm/configs/vf610m4_defconfig:# CONFIG_MMU is not set
> >
> >>
> >> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> >> index d006668c0027d2..e0dae570a51530 100644
> >> --- a/kernel/dma/Kconfig
> >> +++ b/kernel/dma/Kconfig
> >> @@ -71,6 +71,7 @@ config SWIOTLB
> >>  # in the pagetables
> >>  #
> >>  config DMA_NONCOHERENT_MMAP
> >> +    default y if !MMU
> >>      bool
> >
> > Nit: def_bool !MMU
> >
> >>
> >>  config DMA_REMAP
> >> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> >> index 0a4881e59aa7d6..9ec6a5c3fc578c 100644
> >> --- a/kernel/dma/direct.c
> >> +++ b/kernel/dma/direct.c
> >> @@ -459,7 +459,6 @@ int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,
> >>      return ret;
> >>  }
> >>
> >> -#ifdef CONFIG_MMU
> >>  bool dma_direct_can_mmap(struct device *dev)
> >>  {
> >>      return dev_is_dma_coherent(dev) ||
> >> @@ -485,19 +484,6 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
> >>      return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
> >>                      user_count << PAGE_SHIFT, vma->vm_page_prot);
> >>  }
> >> -#else /* CONFIG_MMU */
> >> -bool dma_direct_can_mmap(struct device *dev)
> >> -{
> >> -    return false;
> >> -}
> >> -
> >> -int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
> >> -            void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >> -            unsigned long attrs)
> >> -{
> >> -    return -ENXIO;
> >> -}
> >> -#endif /* CONFIG_MMU */
> >>
> >>  int dma_direct_supported(struct device *dev, u64 mask)
> >>  {
> >>
> >
> > LGTM. FWIW:
> >
> > Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
> >
> >
>
> @dillon, can you give it a try?
>
> I think Christoph would appreciate your Tested-by and that might speed up
> getting fix mainline.
>
sorry for the late response. Yes, it's working

Thanks Christoph

index 8f4bbdaf965e..3e0ecf0b5fb3 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -427,7 +427,6 @@ int dma_direct_get_sgtable(struct device *dev,
struct sg_table *sgt,
        return ret;
 }

-#ifdef CONFIG_MMU
 bool dma_direct_can_mmap(struct device *dev)
 {
        return dev_is_dma_coherent(dev) ||
@@ -453,19 +452,6 @@ int dma_direct_mmap(struct device *dev, struct
vm_area_struct *vma,
        return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
                        user_count << PAGE_SHIFT, vma->vm_page_prot);
 }
-#else /* CONFIG_MMU */
-bool dma_direct_can_mmap(struct device *dev)
-{
-       return false;
-}
-
-int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
-               void *cpu_addr, dma_addr_t dma_addr, size_t size,
-               unsigned long attrs)
-{
-       return -ENXIO;
-}
-#endif /* CONFIG_MMU */

Tested-by:  dillon min <dillon.minfei@gmail.com>

>
> Cheers
> Vladimir
>
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >
>