Hello,
On Thursday, March 22, 2012 2:45 PM Subash Patel wrote:
> I have found out an issue with dma_mmap_writecombine() and coherent devices.
>
> On 02/29/2012 08:34 PM, Marek Szyprowski wrote:
> > This patch converts dma_alloc/free/mmap_{coherent,writecombine}
> > functions to use generic alloc/free/mmap methods from dma_map_ops
> > structure. A new DMA_ATTR_WRITE_COMBINE DMA attribute have been
> > introduced to implement writecombine methods.
> >
> > Signed-off-by: Marek Szyprowski<m.szyprowski@xxxxxxxxxxx>
> > Signed-off-by: Kyungmin Park<kyungmin.park@xxxxxxxxxxx>
> > ---
> > arch/arm/common/dmabounce.c | 3 +
> > arch/arm/include/asm/dma-mapping.h | 107 ++++++++++++++++++++++++++----------
> > arch/arm/mm/dma-mapping.c | 53 ++++++------------
> > 3 files changed, 98 insertions(+), 65 deletions(-)
> >
> > diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
> > index 119f487..dbae5ad 100644
> > --- a/arch/arm/common/dmabounce.c
> > +++ b/arch/arm/common/dmabounce.c
> > @@ -449,6 +449,9 @@ static int dmabounce_set_mask(struct device *dev, u64 dma_mask)
> > }
> >
> > static struct dma_map_ops dmabounce_ops = {
> > + .alloc = arm_dma_alloc,
> > + .free = arm_dma_free,
> > + .mmap = arm_dma_mmap,
> > .map_page = dmabounce_map_page,
> > .unmap_page = dmabounce_unmap_page,
> > .sync_single_for_cpu = dmabounce_sync_for_cpu,
> > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > index 266cba6..4342b75 100644
> > --- a/arch/arm/include/asm/dma-mapping.h
> > +++ b/arch/arm/include/asm/dma-mapping.h
> > @@ -5,6 +5,7 @@
> >
> > #include<linux/mm_types.h>
> > #include<linux/scatterlist.h>
> > +#include<linux/dma-attrs.h>
> > #include<linux/dma-debug.h>
> >
> > #include<asm-generic/dma-coherent.h>
> > @@ -110,68 +111,115 @@ static inline void dma_free_noncoherent(struct device *dev, size_t
> size,
> > extern int dma_supported(struct device *dev, u64 mask);
> >
> > /**
> > - * dma_alloc_coherent - allocate consistent memory for DMA
> > + * arm_dma_alloc - allocate consistent memory for DMA
> > * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> > * @size: required memory size
> > * @handle: bus-specific DMA address
> > + * @attrs: optinal attributes that specific mapping properties
> > *
> > - * Allocate some uncached, unbuffered memory for a device for
> > - * performing DMA. This function allocates pages, and will
> > - * return the CPU-viewed address, and sets @handle to be the
> > - * device-viewed address.
> > + * Allocate some memory for a device for performing DMA. This function
> > + * allocates pages, and will return the CPU-viewed address, and sets @handle
> > + * to be the device-viewed address.
> > */
> > -extern void *dma_alloc_coherent(struct device *, size_t, dma_addr_t *, gfp_t);
> > +extern void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> > + gfp_t gfp, struct dma_attrs *attrs);
> > +
> > +#define dma_alloc_coherent(d,s,h,f) dma_alloc_attrs(d,s,h,f,NULL)
> > +
> > +static inline void *dma_alloc_attrs(struct device *dev, size_t size,
> > + dma_addr_t *dma_handle, gfp_t flag,
> > + struct dma_attrs *attrs)
> > +{
> > + struct dma_map_ops *ops = get_dma_ops(dev);
> > + void *cpu_addr;
> > + BUG_ON(!ops);
> > +
> > + cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
> > + debug_dma_alloc_coherent(dev, size, *dma_handle, cpu_addr);
> > + return cpu_addr;
> > +}
> >
> > /**
> > - * dma_free_coherent - free memory allocated by dma_alloc_coherent
> > + * arm_dma_free - free memory allocated by arm_dma_alloc
> > * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> > * @size: size of memory originally requested in dma_alloc_coherent
> > * @cpu_addr: CPU-view address returned from dma_alloc_coherent
> > * @handle: device-view address returned from dma_alloc_coherent
> > + * @attrs: optinal attributes that specific mapping properties
> > *
> > * Free (and unmap) a DMA buffer previously allocated by
> > - * dma_alloc_coherent().
> > + * arm_dma_alloc().
> > *
> > * References to memory and mappings associated with cpu_addr/handle
> > * during and after this call executing are illegal.
> > */
> > -extern void dma_free_coherent(struct device *, size_t, void *, dma_addr_t);
> > +extern void arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
> > + dma_addr_t handle, struct dma_attrs *attrs);
> > +
> > +#define dma_free_coherent(d,s,c,h) dma_free_attrs(d,s,c,h,NULL)
> > +
> > +static inline void dma_free_attrs(struct device *dev, size_t size,
> > + void *cpu_addr, dma_addr_t dma_handle,
> > + struct dma_attrs *attrs)
> > +{
> > + struct dma_map_ops *ops = get_dma_ops(dev);
> > + BUG_ON(!ops);
> > +
> > + debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
> > + ops->free(dev, size, cpu_addr, dma_handle, attrs);
> > +}
> >
> > /**
> > - * dma_mmap_coherent - map a coherent DMA allocation into user space
> > + * arm_dma_mmap - map a coherent DMA allocation into user space
> > * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> > * @vma: vm_area_struct describing requested user mapping
> > * @cpu_addr: kernel CPU-view address returned from dma_alloc_coherent
> > * @handle: device-view address returned from dma_alloc_coherent
> > * @size: size of memory originally requested in dma_alloc_coherent
> > + * @attrs: optinal attributes that specific mapping properties
> > *
> > * Map a coherent DMA buffer previously allocated by dma_alloc_coherent
> > * into user space. The coherent DMA buffer must not be freed by the
> > * driver until the user space mapping has been released.
> > */
> > -int dma_mmap_coherent(struct device *, struct vm_area_struct *,
> > - void *, dma_addr_t, size_t);
> > +extern int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> > + void *cpu_addr, dma_addr_t dma_addr, size_t size,
> > + struct dma_attrs *attrs);
> >
> > +#define dma_mmap_coherent(d,v,c,h,s) dma_mmap_attrs(d,v,c,h,s,NULL)
> >
> > -/**
> > - * dma_alloc_writecombine - allocate writecombining memory for DMA
> > - * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> > - * @size: required memory size
> > - * @handle: bus-specific DMA address
> > - *
> > - * Allocate some uncached, buffered memory for a device for
> > - * performing DMA. This function allocates pages, and will
> > - * return the CPU-viewed address, and sets @handle to be the
> > - * device-viewed address.
> > - */
> > -extern void *dma_alloc_writecombine(struct device *, size_t, dma_addr_t *,
> > - gfp_t);
> > +static inline int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
> > + void *cpu_addr, dma_addr_t dma_addr,
> > + size_t size, struct dma_attrs *attrs)
> > +{
> > + struct dma_map_ops *ops = get_dma_ops(dev);
> > + BUG_ON(!ops);
> > + return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
> > +}
> >
> > -#define dma_free_writecombine(dev,size,cpu_addr,handle) \
> > - dma_free_coherent(dev,size,cpu_addr,handle)
> > +static inline void *dma_alloc_writecombine(struct device *dev, size_t size,
> > + dma_addr_t *dma_handle, gfp_t flag)
> > +{
> > + DEFINE_DMA_ATTRS(attrs);
> > + dma_set_attr(DMA_ATTR_WRITE_COMBINE,&attrs);
> > + return dma_alloc_attrs(dev, size, dma_handle, flag,&attrs);
> > +}
> >
> > -int dma_mmap_writecombine(struct device *, struct vm_area_struct *,
> > - void *, dma_addr_t, size_t);
> > +static inline void dma_free_writecombine(struct device *dev, size_t size,
> > + void *cpu_addr, dma_addr_t dma_handle)
> > +{
> > + DEFINE_DMA_ATTRS(attrs);
> > + dma_set_attr(DMA_ATTR_WRITE_COMBINE,&attrs);
> > + return dma_free_attrs(dev, size, cpu_addr, dma_handle,&attrs);
> > +}
> > +
> > +static inline int dma_mmap_writecombine(struct device *dev, struct vm_area_struct *vma,
> > + void *cpu_addr, dma_addr_t dma_addr, size_t size)
> > +{
> > + DEFINE_DMA_ATTRS(attrs);
> > + dma_set_attr(DMA_ATTR_WRITE_COMBINE,&attrs);
> > + return dma_mmap_attrs(dev, vma, cpu_addr, dma_addr, size,&attrs);
> > +}
> >
> For devices, which do not have a coherent/reserved pool, then the
> allocation in function __dma_alloc() happens, and the memory will be
> remapped by calling __dma_alloc_remap(). In the above function,
> arm_vmregion_find() will be called, and it succeeds to get the map and
> it will be mapped to used.
>
> This has issues with devices with coherent memory. If we have any device
> which has declared coherent memory, then the allocation happens from
> per-device coherent area. Eg: Exynos MFC which declares:
> s5p_mfc_reserve_mem(). In that case, dma_mmap_writecombine() fails, and
> hence vb2_dc_mmap() fails as well.
Right, I missed that case. Now I prepared a fix, I will send the patches in a minute.
Please check if it works for you.
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
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