On 15/02/17 09:59, Vladimir Murzin wrote:
> dma_declare_coherent_memory() and friends are designed to account
> difference in CPU and device addresses. However, when it is used with
> reserved memory regions there is assumption that CPU and device have
> the same view on address space. This assumption gets invalid when
> reserved memory for coherent DMA allocations is referenced by device
> with non-empty "dma-range" property.
>
> Simply feeding device address as rmem->base + dev->dma_pfn_offset
> would not work due to reserved memory region can be shared, so this
> patch turns device address to be expressed with help of CPU address
> and device's dma_pfn_offset.
>
> For the case where device tree is not used and device sees memory
> different to CPU we explicitly set device's dma_pfn_offset to
> accomplish such difference. The latter might look controversial, but
> it seems only a few drivers set device address different to CPU's:
> - drivers/usb/host/ohci-sm501.c
> - arch/sh/drivers/pci/fixups-dreamcast.c
> so they can be screwed only if dma_pfn_offset there is set and not in
> sync with device address range - we try to catch such cases with
> WARN_ON.
>
> Cc: Michal Nazarewicz <min...@mina86.com>
> Cc: Marek Szyprowski <m.szyprow...@samsung.com>
> Cc: Alan Stern <st...@rowland.harvard.edu>
> Cc: Yoshinori Sato <ys...@users.sourceforge.jp>
> Cc: Rich Felker <dal...@libc.org>
> Cc: Roger Quadros <rog...@ti.com>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Tested-by: Benjamin Gaignard <benjamin.gaign...@linaro.org>
> Tested-by: Andras Szemzo <s...@esh.hu>
> Tested-by: Alexandre TORGUE <alexandre.tor...@st.com>
> Signed-off-by: Vladimir Murzin <vladimir.mur...@arm.com>
> ---
> drivers/base/dma-coherent.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index 640a7e6..c59708c 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -18,6 +18,12 @@ struct dma_coherent_mem {
> spinlock_t spinlock;
> };
>
> +static inline dma_addr_t dma_get_device_base(struct device *dev,
> + struct dma_coherent_mem * mem)
> +{
> + return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
> +}
> +
> static bool dma_init_coherent_memory(
> phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
> struct dma_coherent_mem **mem)
> @@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct
> dma_coherent_mem *mem)
> static int dma_assign_coherent_memory(struct device *dev,
> struct dma_coherent_mem *mem)
> {
> + unsigned long dma_pfn_offset = mem->pfn_base -
> PFN_DOWN(mem->device_base);
> +
> if (dev->dma_mem)
> return -EBUSY;
>
> + if (dev->dma_pfn_offset)
> + WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset !=
> dma_pfn_offset));
> + else
> + dev->dma_pfn_offset = dma_pfn_offset;
This makes me rather uneasy - I can well imagine a device sharing the
CPU physical address map of external system memory, but having its own
view of its local coherent memory such that pfn_base != device_base
still. I know for a fact we've had internal FPGA tiles set up that way,
although whether it was entirely intentional is another matter... ;)
In that situation, setting dev->dma_pfn_offset like this would break
streaming DMA for such devices. Could we not keep the pool-specific
offset and the device-specific offset independent, apply whichever is
non-zero, and scream if both are set?
Robin.
> +
> dev->dma_mem = mem;
> /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>
> @@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device
> *dev,
> return ERR_PTR(-EINVAL);
>
> spin_lock_irqsave(&mem->spinlock, flags);
> - pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
> + pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
> err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
> spin_unlock_irqrestore(&mem->spinlock, flags);
>
> @@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t
> size,
> /*
> * Memory was found in the per-device area.
> */
> - *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
> + *dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
> *ret = mem->virt_base + (pageno << PAGE_SHIFT);
> dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
> spin_unlock_irqrestore(&mem->spinlock, flags);
>
