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commit56406e017aupstream. The commit3bc04e28a0("usb: dwc2: host: Get aligned DMA in a more supported way") introduced a common way to align DMA allocations. The code in the commit aligns the struct dma_aligned_buffer but the actual DMA address pointed by data[0] gets aligned to an offset from the allocated boundary by the kmalloc_ptr and the old_xfer_buffer pointers. This is against the recommendation in Documentation/DMA-API.txt which states: Therefore, it is recommended that driver writers who don't take special care to determine the cache line size at run time only map virtual regions that begin and end on page boundaries (which are guaranteed also to be cache line boundaries). The effect of this is that architectures with non-coherent DMA caches may run into memory corruption or kernel crashes with Unhandled kernel unaligned accesses exceptions. Fix the alignment by positioning the DMA area in front of the allocation and use memory at the end of the area for storing the orginal transfer_buffer pointer. This may have the added benefit of increased performance as the DMA area is now fully aligned on all architectures. Tested with Lantiq xRX200 (MIPS) and RPi Model B Rev 2 (ARM). Fixes:3bc04e28a0("usb: dwc2: host: Get aligned DMA in a more supported way") Cc: <stable@vger.kernel.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> [ Antti: backported to 4.9: edited difference in whitespace ] Signed-off-by: Antti Seppälä <a.seppala@gmail.com> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.