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On Tegra186 and later, a portion of the SYSRAM may be reserved for use by TZ. Non-TZ memory accesses to this portion, including speculative accesses, trigger SErrors that bring down the system. This does also happen in practice occasionally (due to speculative accesses). To fix the issue, add a flag to the SRAM driver to only map the device tree-specified reserved areas depending on a flag set based on the compatibility string. This would not affect non-Tegra systems that rely on the entire thing being memory mapped. If 64K pages are being used, we cannot exactly map the 4K regions that are placed in SYSRAM - ioremap code instead aligns to closest 64K pages. However, since in practice the non-accessible memory area is 64K aligned, these mappings do not overlap with the non-accessible memory area and things work out. Reviewed-by: Mian Yousaf Kaukab <ykaukab@suse.de> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com> Link: https://lore.kernel.org/r/20210715103423.1811101-1-mperttunen@nvidia.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
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.