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The Renesas uPD72020x XHCI controller seems to suffer from a really annoying bug, where it may retain some of its DMA programming across a XHCI reset, and despite the driver correctly programming new DMA addresses. This is visible if the device has been using 64-bit DMA addresses, and is then switched to using 32-bit DMA addresses. The top 32 bits of the address (now zero) are ignored are replaced by the 32 bits from the *previous* programming. Sticking with 64-bit DMA always works, but doesn't seem very appropriate. A PCI reset of the device restores the normal functionality, which is done at probe time. Unfortunately, this has to be done before any quirk has been discovered, hence the intrusive nature of the fix. Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com> CC: stable@vger.kernel.org # v4.11+
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.