On Thu, 19 Aug 2010, Marin Mitov wrote: > Hi all, > > struct device contains a member: struct dma_coherent_mem *dma_mem; > to hold information for a piece of memory declared dma-coherent. > Alternatively the same member could also be used to hold preallocated > dma-coherent memory for latter per-device use. > > This tric is already used in drivers/staging/dt3155v4l.c > dt3155_alloc_coherent()/dt3155_free_coherent() > > Here proposed for general use by popular demand from video4linux folks. > Helps for videobuf-dma-contig framework. Ok, so, we've got two solutions to this problem submitted on the same day;) Following this thread: http://marc.info/?t=128128236400002&r=1&w=2 on the ARM Linux kernel ML, I submitted a patch series http://thread.gmane.org/gmane.linux.ports.sh.devel/8595 with a couple of fixes and improvements, the actual new API and a use example. My approach is slightly different, in that instead of requiring drivers to issue two calls - one to reserve RAM (usually dma_alloc_coherent()) and one to assign it to a device, my patch follows the suggestion from Russell King from the first thread and unites these two operations. So, now we have a choice;) Unfortunately, these two patch series went to orthogonal sets of recepients, I'm trying to fix this by adding a couple of CC entries. Thanks Guennadi > > Signed-off-by: Marin Mitov <mitov@xxxxxxxxxxx> > > ====================================================================== > --- a/drivers/base/dma-coherent.c 2010-08-19 15:50:42.000000000 +0300 > +++ b/drivers/base/dma-coherent.c 2010-08-19 17:27:56.000000000 +0300 > @@ -93,6 +93,83 @@ void *dma_mark_declared_memory_occupied( > EXPORT_SYMBOL(dma_mark_declared_memory_occupied); > > /** > + * dma_reserve_coherent_memory() - reserve coherent memory for per-device use > + * > + * @dev: device from which we allocate memory > + * @size: size of requested memory area in bytes > + * @flags: same as in dma_declare_coherent_memory() > + * > + * This function reserves coherent memory allocating it early (during probe()) > + * to support latter allocations from per-device coherent memory pools. > + * For a given device one could use either dma_declare_coherent_memory() or > + * dma_reserve_coherent_memory(), but not both, becase the result of these > + * functions is stored in a single struct device member - dma_mem > + * > + * Returns DMA_MEMORY_MAP on success, or 0 if failed. > + * (same as dma_declare_coherent_memory() > + */ > +int dma_reserve_coherent_memory(struct device *dev, size_t size, int flags) > +{ > + struct dma_coherent_mem *mem; > + dma_addr_t dev_base; > + int pages = size >> PAGE_SHIFT; > + int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long); > + > + if ((flags & DMA_MEMORY_MAP) == 0) > + goto out; > + if (!size) > + goto out; > + if (dev->dma_mem) > + goto out; > + > + mem = kzalloc(sizeof(*mem), GFP_KERNEL); > + if (!mem) > + goto out; > + mem->virt_base = dma_alloc_coherent(dev, size, &dev_base, > + DT3155_COH_FLAGS); > + if (!mem->virt_base) > + goto err_alloc_coherent; > + mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL); > + if (!mem->bitmap) > + goto err_bitmap; > + > + mem->device_base = dev_base; > + mem->size = pages; > + mem->flags = flags; > + dev->dma_mem = mem; > + return DMA_MEMORY_MAP; > + > +err_bitmap: > + dma_free_coherent(dev, size, mem->virt_base, dev_base); > +err_alloc_coherent: > + kfree(mem); > +out: > + return 0; > +} > +EXPORT_SYMBOL(dma_reserve_coherent_memory); > + > +/** > + * dma_free_reserved_memory() - free the reserved dma-coherent memoty > + * > + * @dev: device for which we free the dma-coherent memory > + * > + * same as dma_release_declared_memory() > + */ > +void dma_free_reserved_memory(struct device *dev) > +{ > + struct dma_coherent_mem *mem = dev->dma_mem; > + > + if (!mem) > + return; > + dev->dma_mem = NULL; > + dma_free_coherent(dev, mem->size << PAGE_SHIFT, > + mem->virt_base, mem->device_base); > + kfree(mem->bitmap); > + kfree(mem); > +} > +EXPORT_SYMBOL(dma_free_reserved_memory); > + > +/** > * dma_alloc_from_coherent() - try to allocate memory from the per-device coherent area > * > * @dev: device from which we allocate memory > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
