56406e017a
The commit 3bc04e28a030 ("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: 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more supported way")
Cc: <stable@vger.kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.