[RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API
From: Guennadi Liakhovetski <hidden>
Date: 2010-08-20 20:05:38
Also in:
linux-media, linux-sh, lkml
Possibly related (same subject, not in this thread)
- 2010-08-28 · Re: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API · Marin Mitov <hidden>
- 2010-08-28 · Re: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API · FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
- 2010-08-28 · Re: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API · Marin Mitov <hidden>
- 2010-08-27 · Re: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API · Marin Mitov <hidden>
- 2010-08-27 · Re: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API · Uwe Kleine-König <hidden>
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
quoted hunk
Signed-off-by: Marin Mitov <redacted> ======================================================================--- 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 at vger.kernel.org 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/