linux-kernel - Re: [PATCH] kernel/dma: export dma_alloc_from

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Message-ID: <1562841861.9534.2.camel@mtkswgap22>
Date:   Thu, 11 Jul 2019 18:44:21 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>,
        <wsd_upstream@...iatek.com>, <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] kernel/dma: export dma_alloc_from_contiguous to modules

On Thu, 2019-07-11 at 09:50 +0100, Robin Murphy wrote:
> On 11/07/2019 06:33, miles.chen@...iatek.com wrote:
> > From: Miles Chen <miles.chen@...iatek.com>
> > 
> > This change exports dma_alloc_from_contiguous and
> > dma_release_from_contiguous to modules.
> > 
> > Currently, we can add a reserve a memory node in dts files, make
> > it a CMA memory by setting compatible = "shared-dma-pool",
> > and setup the dev->cma_area by using of_reserved_mem_device_init_by_idx().
> > 
> > Export dma_alloc_from_contiguous and dma_release_from_contiguous, so we
> > can allocate/free from/to dev->cma_area in kernel modules.
> 
> As far as I understand, this was never intended for drivers to call 
> directly. If a device has its own private CMA area, then regular 
> dma_alloc_attrs() should allocate from that automatically; if that's not 
> happening already, then there's a bug somewhere.
> 
> Robin.

Thanks for your comment. 
After using dma_direct_ops, dma_alloc_attrs() works fine now.

Miles

> 
> > Signed-off-by: Miles Chen <miles.chen@...iatek.com>
> > ---
> >   kernel/dma/contiguous.c | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> > index b2a87905846d..d5920bdedc77 100644
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -197,6 +197,7 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
> >   
> >   	return cma_alloc(dev_get_cma_area(dev), count, align, no_warn);
> >   }
> > +EXPORT_SYMBOL_GPL(dma_alloc_from_contiguous);
> >   
> >   /**
> >    * dma_release_from_contiguous() - release allocated pages
> > @@ -213,6 +214,7 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
> >   {
> >   	return cma_release(dev_get_cma_area(dev), pages, count);
> >   }
> > +EXPORT_SYMBOL_GPL(dma_release_from_contiguous);
> >   
> >   /*
> >    * Support for reserved memory regions defined in device tree
> >