Messages in this thread | | | Date | Wed, 30 Jul 2014 07:33:34 +0200 | From | Marek Szyprowski <> | Subject | Re: [PATCH v2 RESEND 3/4] drivers: dma-coherent: add initialization from device tree |
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Hello,
On 2014-07-29 23:54, Grant Likely wrote: > On Mon, 14 Jul 2014 10:28:06 +0200, Marek Szyprowski <m.szyprowski@samsung.com> wrote: >> Initialization procedure of dma coherent pool has been split into two >> parts, so memory pool can now be initialized without assigning to >> particular struct device. Then initialized region can be assigned to >> more than one struct device. To protect from concurent allocations from >> different devices, a spinlock has been added to dma_coherent_mem >> structure. The last part of this patch adds support for handling >> 'shared-dma-pool' reserved-memory device tree nodes. >> >> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > I think this looks okay. It isn't in my area of expertise though. > Comments below. > >> --- >> drivers/base/dma-coherent.c | 137 ++++++++++++++++++++++++++++++++++++++------ >> 1 file changed, 118 insertions(+), 19 deletions(-) >> >> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c >> index 7d6e84a51424..7185a4f247e1 100644 >> --- a/drivers/base/dma-coherent.c >> +++ b/drivers/base/dma-coherent.c >> @@ -14,11 +14,14 @@ struct dma_coherent_mem { >> int size; >> int flags; >> unsigned long *bitmap; >> + spinlock_t spinlock; >> }; >> >> -int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, >> - dma_addr_t device_addr, size_t size, int flags) >> +static int dma_init_coherent_memory(phys_addr_t phys_addr, dma_addr_t device_addr, >> + size_t size, int flags, >> + struct dma_coherent_mem **mem) > This is a bit odd. Why wouldn't you return the dma_mem pointer directly > instead of passing in a **mem argument?
Because this function (as a direct successor of dma_declare_coherent_memory) doesn't return typical error codes, but some custom values like DMA_MEMORY_MAP, DMA_MEMORY_IO or zero (which means failure). I wanted to avoid confusion with typical error handling path and IS_ERR/ERR_PTR usage used widely in other functions. This probably should be unified with the rest of kernel some day, but right now I wanted to keep the patch simple and easy to review.
>> { >> + struct dma_coherent_mem *dma_mem = NULL; >> void __iomem *mem_base = NULL; >> int pages = size >> PAGE_SHIFT; >> int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long); >> @@ -27,27 +30,26 @@ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, >> goto out; >> if (!size) >> goto out; >> - if (dev->dma_mem) >> - goto out; >> - >> - /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */ >> >> mem_base = ioremap(phys_addr, size); >> if (!mem_base) >> goto out; >> >> - dev->dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL); >> - if (!dev->dma_mem) >> + dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL); >> + if (!dma_mem) >> goto out; >> - dev->dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL); >> - if (!dev->dma_mem->bitmap) >> + dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL); >> + if (!dma_mem->bitmap) >> goto free1_out; >> >> - dev->dma_mem->virt_base = mem_base; >> - dev->dma_mem->device_base = device_addr; >> - dev->dma_mem->pfn_base = PFN_DOWN(phys_addr); >> - dev->dma_mem->size = pages; >> - dev->dma_mem->flags = flags; >> + dma_mem->virt_base = mem_base; >> + dma_mem->device_base = device_addr; >> + dma_mem->pfn_base = PFN_DOWN(phys_addr); >> + dma_mem->size = pages; >> + dma_mem->flags = flags; >> + spin_lock_init(&dma_mem->spinlock); >> + >> + *mem = dma_mem; >> >> if (flags & DMA_MEMORY_MAP) >> return DMA_MEMORY_MAP; >> @@ -55,12 +57,51 @@ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, >> return DMA_MEMORY_IO; >> >> free1_out: >> - kfree(dev->dma_mem); >> + kfree(dma_mem); >> out: >> if (mem_base) >> iounmap(mem_base); >> return 0; >> } >> + >> +static void dma_release_coherent_memory(struct dma_coherent_mem *mem) >> +{ >> + if (!mem) >> + return; >> + iounmap(mem->virt_base); >> + kfree(mem->bitmap); >> + kfree(mem); >> +} >> + >> +static int dma_assign_coherent_memory(struct device *dev, >> + struct dma_coherent_mem *mem) >> +{ >> + if (dev->dma_mem) >> + return -EBUSY; >> + >> + dev->dma_mem = mem; >> + /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */ >> + >> + return 0; >> +} >> + >> +int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, >> + dma_addr_t device_addr, size_t size, int flags) >> +{ >> + struct dma_coherent_mem *mem; >> + int ret; >> + >> + ret = dma_init_coherent_memory(phys_addr, device_addr, size, flags, >> + &mem); >> + if (ret == 0) >> + return 0; >> + >> + if (dma_assign_coherent_memory(dev, mem) == 0) >> + return ret; >> + >> + dma_release_coherent_memory(mem); >> + return 0; >> +} >> EXPORT_SYMBOL(dma_declare_coherent_memory); >> >> void dma_release_declared_memory(struct device *dev) >> @@ -69,10 +110,8 @@ void dma_release_declared_memory(struct device *dev) >> >> if (!mem) >> return; >> + dma_release_coherent_memory(mem); >> dev->dma_mem = NULL; >> - iounmap(mem->virt_base); >> - kfree(mem->bitmap); >> - kfree(mem); >> } >> EXPORT_SYMBOL(dma_release_declared_memory); >> >> @@ -80,6 +119,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev, >> dma_addr_t device_addr, size_t size) >> { >> struct dma_coherent_mem *mem = dev->dma_mem; >> + unsigned long flags; >> int pos, err; >> >> size += device_addr & ~PAGE_MASK; >> @@ -87,8 +127,11 @@ void *dma_mark_declared_memory_occupied(struct device *dev, >> if (!mem) >> return ERR_PTR(-EINVAL); >> >> + spin_lock_irqsave(&mem->spinlock, flags); >> pos = (device_addr - mem->device_base) >> PAGE_SHIFT; >> err = bitmap_allocate_region(mem->bitmap, pos, get_order(size)); >> + spin_unlock_irqrestore(&mem->spinlock, flags); >> + >> if (err != 0) >> return ERR_PTR(err); >> return mem->virt_base + (pos << PAGE_SHIFT); >> @@ -115,6 +158,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size, >> { >> struct dma_coherent_mem *mem; >> int order = get_order(size); >> + unsigned long flags; >> int pageno; >> >> if (!dev) >> @@ -124,6 +168,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size, >> return 0; >> >> *ret = NULL; >> + spin_lock_irqsave(&mem->spinlock, flags); >> >> if (unlikely(size > (mem->size << PAGE_SHIFT))) >> goto err; >> @@ -138,10 +183,12 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size, >> *dma_handle = mem->device_base + (pageno << PAGE_SHIFT); >> *ret = mem->virt_base + (pageno << PAGE_SHIFT); >> memset(*ret, 0, size); >> + spin_unlock_irqrestore(&mem->spinlock, flags); >> >> return 1; >> >> err: >> + spin_unlock_irqrestore(&mem->spinlock, flags); >> /* >> * In the case where the allocation can not be satisfied from the >> * per-device area, try to fall back to generic memory if the >> @@ -171,8 +218,11 @@ int dma_release_from_coherent(struct device *dev, int order, void *vaddr) >> if (mem && vaddr >= mem->virt_base && vaddr < >> (mem->virt_base + (mem->size << PAGE_SHIFT))) { >> int page = (vaddr - mem->virt_base) >> PAGE_SHIFT; >> + unsigned long flags; >> >> + spin_lock_irqsave(&mem->spinlock, flags); >> bitmap_release_region(mem->bitmap, page, order); >> + spin_unlock_irqrestore(&mem->spinlock, flags); >> return 1; >> } >> return 0; >> @@ -218,3 +268,52 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma, >> return 0; >> } >> EXPORT_SYMBOL(dma_mmap_from_coherent); >> + >> +/* >> + * Support for reserved memory regions defined in device tree >> + */ >> +#ifdef CONFIG_OF_RESERVED_MEM >> +#include <linux/of.h> >> +#include <linux/of_fdt.h> >> +#include <linux/of_reserved_mem.h> >> + >> +static void rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev) >> +{ >> + struct dma_coherent_mem *mem = rmem->priv; > Will the reserved_mem->priv pointer ever point to some other kind of > structure? How do we know that the pointer here is always a > dma_coherent_mem struct (if there are other uses of priv, what is the > guarantee against another user assigning something to it?) Is it the > reserved_mem_ops below that provide the guarantee?
reserved_mem_ops are set by the given reserved memory driver and access to priv pointer is limited only to that driver. This pattern is used widely across the whole kernel, so I don't think that a separate pointer to particular structure type is needed.
> If it is a risk, then the alternative would be to put an explicit > dma_coherent_mem pointer into the reserved_mem structure.
If one messes with priv pointers, he should expect serious problems and we really cannot prevent him anyway.
>> + if (!mem && >> + dma_init_coherent_memory(rmem->base, rmem->base, rmem->size, >> + DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE, >> + &mem) != DMA_MEMORY_MAP) { >> + pr_info("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n", >> + &rmem->base, (unsigned long)rmem->size / SZ_1M); >> + return; >> + } >> + rmem->priv = mem; >> + dma_assign_coherent_memory(dev, mem); >> +} >> + >> +static void rmem_dma_device_release(struct reserved_mem *rmem, >> + struct device *dev) >> +{ >> + dev->dma_mem = NULL; >> +} >> + >> +static const struct reserved_mem_ops rmem_dma_ops = { >> + .device_init = rmem_dma_device_init, >> + .device_release = rmem_dma_device_release, >> +}; >> + >> +static int __init rmem_dma_setup(struct reserved_mem *rmem) >> +{ >> + unsigned long node = rmem->fdt_node; >> + >> + if (of_get_flat_dt_prop(node, "reusable", NULL)) >> + return -EINVAL; >> + >> + rmem->ops = &rmem_dma_ops; >> + pr_info("Reserved memory: created DMA memory pool at %pa, size %ld MiB\n", >> + &rmem->base, (unsigned long)rmem->size / SZ_1M); >> + return 0; >> +} >> +RESERVEDMEM_OF_DECLARE(dma, "shared-dma-pool", rmem_dma_setup); >> +#endif >> -- >> 1.9.2
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
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