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Message-ID: <CACxGe6s2G_vEnmo5LwK79bwkEWSNsegfiojDAdQZV01Wapo0eg@mail.gmail.com>
Date: Wed, 30 Jul 2014 17:49:25 -0600
From: Grant Likely <grant.likely@...aro.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>
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
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?
g.
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