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Date: Tue, 29 Jul 2014 15:54:32 -0600
From: Grant Likely <grant.likely@...aro.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
linaro-mm-sig@...ts.linaro.org, devicetree@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Michal Nazarewicz <mina86@...a86.com>,
Tomasz Figa <t.figa@...sung.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Laura Abbott <lauraa@...eaurora.org>,
Nishanth Peethambaran <nishanth.p@...il.com>,
Marc <marc.ceeeee@...il.com>,
Josh Cartwright <joshc@...eaurora.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Paul Mackerras <paulus@...ba.org>,
Jon Medhurst <tixy@...aro.org>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
"Aneesh Kumar K.V." <aneesh.kumar@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 RESEND 3/4] drivers: dma-coherent: add initialization
from device tree
On Mon, 14 Jul 2014 10:28:06 +0200, Marek Szyprowski <m.szyprowski@...sung.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@...sung.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?
> {
> + 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?
If it is a risk, then the alternative would be to put an explicit
dma_coherent_mem pointer into the reserved_mem structure.
> + 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
>
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