[PATCH v2] ARM: errata: Workaround errata A12 857271 / A17 857272

[PATCH v2] ARM: errata: Workaround errata A12 857271 / A17 857272

[Douglas Anderson]

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 this was treated as two errata: ERRATA_FOOBAR [1] and
ERRATA_CR711784 [2].  Apparently the two errata got lumped together at
some point in time.

Let's actually get the workaround landed.

[1] https://crrev.com/c/342753
[2] https://crbug.com/711784

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

Changes in v2:
- Squashed bits 10 and 11 into one errata.

 arch/arm/Kconfig      | 18 ++++++++++++++++++
 arch/arm/mm/proc-v7.S | 10 ++++++++++
 2 files changed, 28 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b509cd338219..59fdcd51d7ee 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1172,6 +1172,14 @@ 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 < 1% 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 +1201,16 @@ 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..2966086d8a45 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, #3 << 10		@ set bits #10 and #11
+	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, #3 << 10		@ set bits #10 and #11
+	mcr	p15, 0, r10, c15, c0, 1		@ write diagnostic register
 #endif
 	b	__errata_finish
 
-- 
2.21.0.593.g511ec345e18-goog


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Re: [PATCH v2] ARM: errata: Workaround errata A12 857271 / A17 857272

[Doug Anderson]

Hi,

On Tue, Apr 23, 2019 at 4:00 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> 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 this was treated as two errata: ERRATA_FOOBAR [1] and
> ERRATA_CR711784 [2].  Apparently the two errata got lumped together at
> some point in time.
>
> Let's actually get the workaround landed.
>
> [1] https://crrev.com/c/342753
> [2] https://crbug.com/711784
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
> ---
>
> Changes in v2:
> - Squashed bits 10 and 11 into one errata.
>
>  arch/arm/Kconfig      | 18 ++++++++++++++++++
>  arch/arm/mm/proc-v7.S | 10 ++++++++++
>  2 files changed, 28 insertions(+)

Breadcrumbs: this has been submitted to RMK's patch tracking system.  See:

https://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8861/1

-Doug

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