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+ Silicon Errata and Software Workarounds
+ =======================================
+
+Author: Will Deacon <will.deacon@arm.com>
+Date : 27 November 2015
+
+It is an unfortunate fact of life that hardware is often produced with
+so-called "errata", which can cause it to deviate from the architecture
+under specific circumstances. For hardware produced by ARM, these
+errata are broadly classified into the following categories:
+
+ Category A: A critical error without a viable workaround.
+ Category B: A significant or critical error with an acceptable
+ workaround.
+ Category C: A minor error that is not expected to occur under normal
+ operation.
+
+For more information, consult one of the "Software Developers Errata
+Notice" documents available on infocenter.arm.com (registration
+required).
+
+As far as Linux is concerned, Category B errata may require some special
+treatment in the operating system. For example, avoiding a particular
+sequence of code, or configuring the processor in a particular way. A
+less common situation may require similar actions in order to declassify
+a Category A erratum into a Category C erratum. These are collectively
+known as "software workarounds" and are only required in the minority of
+cases (e.g. those cases that both require a non-secure workaround *and*
+can be triggered by Linux).
+
+For software workarounds that may adversely impact systems unaffected by
+the erratum in question, a Kconfig entry is added under "Kernel
+Features" -> "ARM errata workarounds via the alternatives framework".
+These are enabled by default and patched in at runtime when an affected
+CPU is detected. For less-intrusive workarounds, a Kconfig option is not
+available and the code is structured (preferably with a comment) in such
+a way that the erratum will not be hit.
+
+This approach can make it slightly onerous to determine exactly which
+errata are worked around in an arbitrary kernel source tree, so this
+file acts as a registry of software workarounds in the Linux Kernel and
+will be updated when new workarounds are committed and backported to
+stable kernels.
+
+| Implementor | Component | Erratum ID | Kconfig |
++----------------+-----------------+-----------------+-------------------------+
+| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
+| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
+| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
+| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
+| ARM | Cortex-A57 | #852523 | N/A |
+| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
+| | | | |
+| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
+| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
It's not immediately obvious which hardware errata are worked around in the Linux kernel for an arbitrary kernel tree, so add a file to keep track of what we're working around. Signed-off-by: Will Deacon <will.deacon@arm.com> --- Documentation/arm64/silicon-errata.txt | 58 ++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 Documentation/arm64/silicon-errata.txt -- 2.1.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel