Re: [PATCH v3 1/7] device: introduce per device dma_pfn_offset
From: Rob Herring <hidden>
Date: 2014-05-02 01:01:12
Also in:
linux-arm-kernel, lkml
On Thu, Apr 24, 2014 at 10:30 AM, Santosh Shilimkar [off-list ref] wrote:
On few architectures, there are few restrictions on DMAble area of system RAM. That also means that devices needs to know about this restrictions so that the dma_masks can be updated accordingly and dma address translation helpers can add/subtract the dma offset. In most of cases DMA addresses can be performed using offset value of Bus address space relatively to physical address space as following: PFN->DMA: __pfn_to_phys(pfn + [-]dma_pfn_offset) DMA->PFN: __phys_to_pfn(dma_addr) + [-]dma_pfn_offset So we introduce per device dma_pfn_offset which can be popullated by architecture init code while creating the devices. Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Russell King <redacted> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Olof Johansson <redacted> Cc: Grant Likely <redacted> Cc: Rob Herring <robh+dt@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Linus Walleij <redacted> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> Signed-off-by: Santosh Shilimkar <redacted>
Reviewed-by: Rob Herring <robh@kernel.org> Rob
quoted hunk ↗ jump to hunk
--- include/linux/device.h | 2 ++ 1 file changed, 2 insertions(+)diff --git a/include/linux/device.h b/include/linux/device.h index 233bbbe..85a52d6 100644 --- a/include/linux/device.h +++ b/include/linux/device.h@@ -691,6 +691,7 @@ struct acpi_dev_node { * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all * hardware supports 64-bit addresses for consistent allocations * such descriptors. + * @dma_pfn_offset: offset of DMA memory range relatively of RAM * @dma_parms: A low level driver may set these to teach IOMMU code about * segment limitations. * @dma_pools: Dma pools (if dma'ble device).@@ -756,6 +757,7 @@ struct device { not all hardware supports 64 bit addresses for consistent allocations such descriptors. */ + unsigned long dma_pfn_offset; struct device_dma_parameters *dma_parms; --1.7.9.5