Re: [PATCH 5/5] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP

From: Takashi Iwai <tiwai@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xtensa@linux-xtensa.org, Michal Simek <monstr@monstr.eu>,
	linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org,
	Takashi Iwai <tiwai@suse.de>, Robin Murphy <robin.murphy@arm.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org,
	linux-m68k@lists.linux-m68k.org, linuxppc-dev@lists.ozlabs.org,
	linux-arm-kernel@lists.infradead.org,
	Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH 5/5] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP
Date: Fri, 02 Aug 2019 08:24:02 +0000	[thread overview]
Message-ID: <s5hh870rn4t.wl-tiwai@suse.de> (raw)
In-Reply-To: <20190802070354.GA8280@lst.de>

On Fri, 02 Aug 2019 09:03:54 +0200,
Christoph Hellwig wrote:
> 
> Takashi,
> 
> any comments on the sounds/ side of this?

I wasn't careful enough to look at that change, sorry.

The code there tries to check whether dma_mmap_coherent() would always
fail on some platforms.  Then the driver clears the mmap capability
flag at the device open time and notifies user-space to fall back to
the dumb read/write mode.

So I'm afraid that simply dropping the check would cause the behavior
regression, e.g. on PARISC.

Is there any simple way to test whether dma_mmap_coherent() would work
or not in general on the target platform?  It's not necessarily in an
ifdef at all.

thanks,

Takashi

> On Thu, Jul 25, 2019 at 08:34:01AM +0200, Christoph Hellwig wrote:
> > Now that we never use a default ->mmap implementation, and non-coherent
> > architectures can control the presence of ->mmap support by enabling
> > ARCH_HAS_DMA_COHERENT_TO_PFN for the dma direct implementation there
> > is no need for a global config option to control the availability
> > of dma_common_mmap.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  arch/Kconfig            |  3 ---
> >  arch/c6x/Kconfig        |  1 -
> >  arch/m68k/Kconfig       |  1 -
> >  arch/microblaze/Kconfig |  1 -
> >  arch/parisc/Kconfig     |  1 -
> >  arch/sh/Kconfig         |  1 -
> >  arch/xtensa/Kconfig     |  1 -
> >  kernel/dma/mapping.c    |  4 ----
> >  sound/core/pcm_native.c | 10 +---------
> >  9 files changed, 1 insertion(+), 22 deletions(-)
> > 
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index a7b57dd42c26..ec2834206d08 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -790,9 +790,6 @@ config COMPAT_32BIT_TIME
> >  	  This is relevant on all 32-bit architectures, and 64-bit architectures
> >  	  as part of compat syscall handling.
> >  
> > -config ARCH_NO_COHERENT_DMA_MMAP
> > -	bool
> > -
> >  config ARCH_NO_PREEMPT
> >  	bool
> >  
> > diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig
> > index b4fb61c83494..e65e8d82442a 100644
> > --- a/arch/c6x/Kconfig
> > +++ b/arch/c6x/Kconfig
> > @@ -20,7 +20,6 @@ config C6X
> >  	select OF_EARLY_FLATTREE
> >  	select GENERIC_CLOCKEVENTS
> >  	select MODULES_USE_ELF_RELA
> > -	select ARCH_NO_COHERENT_DMA_MMAP
> >  	select MMU_GATHER_NO_RANGE if MMU
> >  
> >  config MMU
> > diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> > index c518d695c376..614b355ae338 100644
> > --- a/arch/m68k/Kconfig
> > +++ b/arch/m68k/Kconfig
> > @@ -8,7 +8,6 @@ config M68K
> >  	select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
> >  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
> >  	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
> > -	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
> >  	select ARCH_NO_PREEMPT if !COLDFIRE
> >  	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
> >  	select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE
> > diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
> > index d411de05b628..632c9477a0f6 100644
> > --- a/arch/microblaze/Kconfig
> > +++ b/arch/microblaze/Kconfig
> > @@ -9,7 +9,6 @@ config MICROBLAZE
> >  	select ARCH_HAS_SYNC_DMA_FOR_CPU
> >  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> >  	select ARCH_MIGHT_HAVE_PC_PARPORT
> > -	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
> >  	select ARCH_WANT_IPC_PARSE_VERSION
> >  	select BUILDTIME_EXTABLE_SORT
> >  	select TIMER_OF
> > diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
> > index 6d732e451071..e9dd88b7f81e 100644
> > --- a/arch/parisc/Kconfig
> > +++ b/arch/parisc/Kconfig
> > @@ -52,7 +52,6 @@ config PARISC
> >  	select GENERIC_SCHED_CLOCK
> >  	select HAVE_UNSTABLE_SCHED_CLOCK if SMP
> >  	select GENERIC_CLOCKEVENTS
> > -	select ARCH_NO_COHERENT_DMA_MMAP
> >  	select CPU_NO_EFFICIENT_FFS
> >  	select NEED_DMA_MAP_STATE
> >  	select NEED_SG_DMA_LENGTH
> > diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> > index 6b1b5941b618..f356ee674d89 100644
> > --- a/arch/sh/Kconfig
> > +++ b/arch/sh/Kconfig
> > @@ -5,7 +5,6 @@ config SUPERH
> >  	select ARCH_HAS_PTE_SPECIAL
> >  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> >  	select ARCH_MIGHT_HAVE_PC_PARPORT
> > -	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
> >  	select HAVE_PATA_PLATFORM
> >  	select CLKDEV_LOOKUP
> >  	select DMA_DECLARE_COHERENT
> > diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
> > index ebc135bda921..70653aed3005 100644
> > --- a/arch/xtensa/Kconfig
> > +++ b/arch/xtensa/Kconfig
> > @@ -5,7 +5,6 @@ config XTENSA
> >  	select ARCH_HAS_BINFMT_FLAT if !MMU
> >  	select ARCH_HAS_SYNC_DMA_FOR_CPU
> >  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> > -	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
> >  	select ARCH_USE_QUEUED_RWLOCKS
> >  	select ARCH_USE_QUEUED_SPINLOCKS
> >  	select ARCH_WANT_FRAME_POINTERS
> > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> > index 7dff1829c8c5..815446f76995 100644
> > --- a/kernel/dma/mapping.c
> > +++ b/kernel/dma/mapping.c
> > @@ -169,7 +169,6 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> >  		void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >  		unsigned long attrs)
> >  {
> > -#ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP
> >  	unsigned long user_count = vma_pages(vma);
> >  	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> >  	unsigned long off = vma->vm_pgoff;
> > @@ -198,9 +197,6 @@ int dma_common_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
> > -	return -ENXIO;
> > -#endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
> >  }
> >  
> >  /**
> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > index 860543a4c840..2dadc708343a 100644
> > --- a/sound/core/pcm_native.c
> > +++ b/sound/core/pcm_native.c
> > @@ -218,15 +218,7 @@ int snd_pcm_info_user(struct snd_pcm_substream *substream,
> >  
> >  static bool hw_support_mmap(struct snd_pcm_substream *substream)
> >  {
> > -	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
> > -		return false;
> > -	/* architecture supports dma_mmap_coherent()? */
> > -#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
> > -	if (!substream->ops->mmap &&
> > -	    substream->dma_buffer.dev.type = SNDRV_DMA_TYPE_DEV)
> > -		return false;
> > -#endif
> > -	return true;
> > +	return substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP;
> >  }
> >  
> >  static int constrain_mask_params(struct snd_pcm_substream *substream,
> > -- 
> > 2.20.1
> > 
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> ---end quoted text---
> 