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Date: Thu, 31 Jul 2014 07:15:08 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Grant Likely <grant.likely@...aro.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
"devicetree@...r.kernel.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 2014-07-31 01:49, Grant Likely wrote:
> On Tue, Jul 29, 2014 at 11:33 PM, Marek Szyprowski
> <m.szyprowski@...sung.com> wrote:
>> 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.
> Yup, that's fine. I wanted to make sure.
>
> Do I need to be taking these patches through the DT tree? Do patches 3
> & 4 make sense without patch 2?
Patches 3 and 4 are independent from patch 1&2. Patch 4 depends on the
other CMA
patches, which has been merged to akpm tree. I think the easiest
solution would
be to get your Ack for both patches and I will ask Andrew Morton to take
them
together with other mm/CMA changes.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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