| Message ID | 1484826406-16348-2-git-send-email-dingtianhong@huawei.com |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: arch_timer: Add workaround for hisilicon-161010101 erratum | expand |
On Thu, Jan 19, 2017 at 07:46:43PM +0800, Ding Tianhong wrote: > This erratum describes a bug in logic outside the core, so MIDR can't be > used to identify its presence, and reading an SoC-specific revision > register from common arch timer code would be awkward. So, describe it > in the device tree. > > Signed-off-by: Ding Tianhong <dingtianhong@huawei.com> > Acked-by: Rob Herring <robh@kernel.org> > --- > Documentation/devicetree/bindings/arm/arch_timer.txt | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt > index ad440a2..9116934 100644 > --- a/Documentation/devicetree/bindings/arm/arch_timer.txt > +++ b/Documentation/devicetree/bindings/arm/arch_timer.txt > @@ -31,6 +31,14 @@ to deliver its interrupts via SPIs. > This also affects writes to the tval register, due to the implicit > counter read. > > +- hisilicon,erratum-161010101 : A boolean property. Indicates the presence of > + erratum 161010101, which says that reading the counter is unreliable unless > + reading twice on the register and the value of the second read is larger > + than the first by less than 32. If the verification is unsuccessful, then > + discard the value of this read and repeat this procedure until the verification > + is successful. This also affects writes to the tval register, due to the > + implicit counter read. This describes the workaround, which shouldn't be necessary. My understanding (from the cover letter) is that reads of the {virtual,physical} counters may return a value precisely 32 above the true value. So it would be better to say: - hisilicon,erratum-161010101 : A boolean property. Indicates the presence of Hisilicon erratum 161010101, which says that reading the counters is unreliable in some cases, and reads may return a value 32 beyond the correct value. This also affects writes to the tval registers, due to the implicit counter read. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 2017/1/19 20:10, Mark Rutland wrote: > On Thu, Jan 19, 2017 at 07:46:43PM +0800, Ding Tianhong wrote: >> This erratum describes a bug in logic outside the core, so MIDR can't be >> used to identify its presence, and reading an SoC-specific revision >> register from common arch timer code would be awkward. So, describe it >> in the device tree. >> >> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com> >> Acked-by: Rob Herring <robh@kernel.org> >> --- >> Documentation/devicetree/bindings/arm/arch_timer.txt | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt >> index ad440a2..9116934 100644 >> --- a/Documentation/devicetree/bindings/arm/arch_timer.txt >> +++ b/Documentation/devicetree/bindings/arm/arch_timer.txt >> @@ -31,6 +31,14 @@ to deliver its interrupts via SPIs. >> This also affects writes to the tval register, due to the implicit >> counter read. >> >> +- hisilicon,erratum-161010101 : A boolean property. Indicates the presence of >> + erratum 161010101, which says that reading the counter is unreliable unless >> + reading twice on the register and the value of the second read is larger >> + than the first by less than 32. If the verification is unsuccessful, then >> + discard the value of this read and repeat this procedure until the verification >> + is successful. This also affects writes to the tval register, due to the >> + implicit counter read. > > This describes the workaround, which shouldn't be necessary. > > My understanding (from the cover letter) is that reads of the > {virtual,physical} counters may return a value precisely 32 above the > true value. > > So it would be better to say: > > - hisilicon,erratum-161010101 : A boolean property. Indicates the > presence of Hisilicon erratum 161010101, which says that reading the > counters is unreliable in some cases, and reads may return a value 32 > beyond the correct value. This also affects writes to the tval > registers, due to the implicit counter read. > > Thanks, > Mark. Looks more accurate. Thanks. Ding > > . > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt index ad440a2..9116934 100644 --- a/Documentation/devicetree/bindings/arm/arch_timer.txt +++ b/Documentation/devicetree/bindings/arm/arch_timer.txt @@ -31,6 +31,14 @@ to deliver its interrupts via SPIs. This also affects writes to the tval register, due to the implicit counter read. +- hisilicon,erratum-161010101 : A boolean property. Indicates the presence of + erratum 161010101, which says that reading the counter is unreliable unless + reading twice on the register and the value of the second read is larger + than the first by less than 32. If the verification is unsuccessful, then + discard the value of this read and repeat this procedure until the verification + is successful. This also affects writes to the tval register, due to the + implicit counter read. + ** Optional properties: - arm,cpu-registers-not-fw-configured : Firmware does not initialize