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Message-id: <53D883AE.6030209@samsung.com>
Date: Wed, 30 Jul 2014 07:33:34 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Grant Likely <grant.likely@...aro.org>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: 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
Hello,
On 2014-07-29 23:54, Grant Likely wrote:
> 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?
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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