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Subject[PATCH 1/2] ARM: errata: Workaround errata A12 857271 / A17 857272
Date
From: Sonny Rao <sonnyrao@chromium.org>

This adds support for working around errata A12 857271 / A17 857272.
These errata were causing hangs on rk3288-based Chromebooks and it was
confirmed that this workaround fixed the problems. In the Chrome OS
3.14 kernel [1] this erratum was known as ERRATA_FOOBAR due to lack of
an official number from ARM (though the workaround of setting chicken
bit 10 came from ARM). In the meantime ARM came up with official
errata numbers but never published the workaround upstream.

Let's actually get the workaround landed.

[1] https://crrev.com/c/342753

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

arch/arm/Kconfig | 19 +++++++++++++++++++
arch/arm/mm/proc-v7.S | 10 ++++++++++
2 files changed, 29 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b509cd338219..4376fe74f95e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1172,6 +1172,15 @@ config ARM_ERRATA_825619
DMB NSHST or DMB ISHST instruction followed by a mix of Cacheable
and Device/Strongly-Ordered loads and stores might cause deadlock

+config ARM_ERRATA_857271
+ bool "ARM errata: A12: CPU might deadlock under some very rare internal conditions"
+ depends on CPU_V7
+ help
+ This option enables the workaround for the 857271 Cortex-A12
+ (all revs) erratum. Under very rare timing conditions, the CPU might
+ hang. The workaround is expected to have a negligible performance
+ impact.
+
config ARM_ERRATA_852421
bool "ARM errata: A17: DMB ST might fail to create order between stores"
depends on CPU_V7
@@ -1193,6 +1202,16 @@ config ARM_ERRATA_852423
config option from the A12 erratum due to the way errata are checked
for and handled.

+config ARM_ERRATA_857272
+ bool "ARM errata: A17: CPU might deadlock under some very rare internal conditions"
+ depends on CPU_V7
+ help
+ This option enables the workaround for the 857272 Cortex-A17 erratum.
+ This erratum is not known to be fixed in any A17 revision.
+ This is identical to Cortex-A12 erratum 857271. It is a separate
+ config option from the A12 erratum due to the way errata are checked
+ for and handled.
+
endmenu

source "arch/arm/common/Kconfig"
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 339eb17c9808..cd2accbab844 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -391,6 +391,11 @@ __ca12_errata:
mrc p15, 0, r10, c15, c0, 1 @ read diagnostic register
orr r10, r10, #1 << 24 @ set bit #24
mcr p15, 0, r10, c15, c0, 1 @ write diagnostic register
+#endif
+#ifdef CONFIG_ARM_ERRATA_857271
+ mrc p15, 0, r10, c15, c0, 1 @ read diagnostic register
+ orr r10, r10, #1 << 10 @ set bit #10
+ mcr p15, 0, r10, c15, c0, 1 @ write diagnostic register
#endif
b __errata_finish

@@ -406,6 +411,11 @@ __ca17_errata:
mrcle p15, 0, r10, c15, c0, 1 @ read diagnostic register
orrle r10, r10, #1 << 12 @ set bit #12
mcrle p15, 0, r10, c15, c0, 1 @ write diagnostic register
+#endif
+#ifdef CONFIG_ARM_ERRATA_857272
+ mrc p15, 0, r10, c15, c0, 1 @ read diagnostic register
+ orr r10, r10, #1 << 10 @ set bit #10
+ mcr p15, 0, r10, c15, c0, 1 @ write diagnostic register
#endif
b __errata_finish

--
2.21.0.593.g511ec345e18-goog
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