This reverts commit d7bd554f27.
It turns out that Tegra20 has a bug in the implementation of the MSI
target address register (which is worked around by the existence of the
struct tegra_pcie_soc.msi_base_shift parameter) that restricts the MSI
target memory to the lower 32 bits of physical memory on that particular
generation. The offending patch causes a regression on TrimSlice, which
is a Tegra20-based device and has a PCI network interface card.
An initial, simpler fix was to change the MSI target address for Tegra20
only, but it was pointed out that the offending commit also prevents the
use of 32-bit only MSI capable devices, even on later chips. Technically
this was never guaranteed to work with the prior code in the first place
because the allocated page could have resided beyond the 4 GiB boundary,
but it is still possible that this could've introduced a regression.
The proper fix that was settled on is to select a fixed address within
the lowest 32 bits of physical address space that is otherwise unused,
but testing of that patch has provided mixed results that are not fully
understood yet.
Given all of the above and the relative urgency to get this fixed in
v4.13, revert the offending commit until a universal fix is found.
Fixes: d7bd554f27 ("PCI: tegra: Do not allocate MSI target memory")
Reported-by: Tomasz Maciej Nowak <tmn505@gmail.com>
Reported-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org # 4.13.x
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.
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