[PATCH v2 3/4] arm64: arch_timer: Work around Erratum Hisilicon-161601
Ding Tianhong
dingtianhong at huawei.com
Thu Oct 27 00:34:10 PDT 2016
Erratum Hisilicon-161601 says that the ARM generic timer counter "has the
potential to contain an erroneous value when the timer value changes".
Accesses to TVAL (both read and write) are also affected due to the implicit counter
read. Accesses to CVAL are not affected.
The workaround is to reread the system count registers until the value of the second
read is larger than the first one by less than 32, the system counter can be guaranteed
not to return wrong value twice by back-to-back read and the error value is always larger
than the correct one by 32. Writes to TVAL are replaced with an equivalent write to CVAL.
The workaround is enabled if the hisilicon,erratum-161601 property is found in
the timer node in the device tree. This can be overridden with the
clocksource.arm_arch_timer.hisilicon-161601 boot parameter, which allows KVM
users to enable the workaround until a mechanism is implemented to
automatically communicate this information.
Fix some description for fsl erratum a008585.
v2: Significant rework based on feedback, including seperate the fsl erratum a008585
to another patch, update the erratum name and remove unwanted code.
Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
---
Documentation/arm64/silicon-errata.txt | 1 +
Documentation/kernel-parameters.txt | 9 ++++
arch/arm64/include/asm/arch_timer.h | 28 ++++++++++-
drivers/clocksource/Kconfig | 14 +++++-
drivers/clocksource/arm_arch_timer.c | 88 ++++++++++++++++++++++++++--------
5 files changed, 118 insertions(+), 22 deletions(-)
diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index 405da11..70c5d5e 100644
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -63,3 +63,4 @@ stable kernels.
| Cavium | ThunderX SMMUv2 | #27704 | N/A |
| | | | |
| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
+| Hisilicon | Hip05/Hip06/Hip07 | #161601 | HISILICON_ERRATUM_161601|
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6fa1d8a..735b4b6 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -707,6 +707,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
erratum. If unspecified, the workaround is
enabled based on the device tree.
+ clocksource.arm_arch_timer.hisilicon-161601=
+ [ARM64]
+ Format: <bool>
+ Enable/disable the workaround of Hisilicon
+ erratum 161601. This can be useful for KVM
+ guests, if the guest device tree doesn't show the
+ erratum. If unspecified, the workaround is
+ enabled based on the device tree.
+
clearcpuid=BITNUM [X86]
Disable CPUID feature X for the kernel. See
arch/x86/include/asm/cpufeatures.h for the valid bit
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index 118719d8..49b3041 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -29,7 +29,7 @@
#include <clocksource/arm_arch_timer.h>
-#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585)
+#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585) || IS_ENABLED(CONFIG_HISILICON_ERRATUM_161601)
extern struct static_key_false arch_timer_read_ool_enabled;
#define needs_timer_erratum_workaround() \
static_branch_unlikely(&arch_timer_read_ool_enabled)
@@ -65,11 +65,35 @@ extern struct arch_timer_erratum_workaround *erratum_workaround;
_new; \
})
+
+
+/*
+ * The number of retries is an arbitrary value well beyond the highest number
+ * of iterations the loop has been observed to take.
+ * Verify whether the value of the second read is larger than the first by
+ * less than 32 is the only way to confirm the value is correct, the system
+ * counter can be guaranteed not to return wrong value twice by back-to-back read
+ * and the error value is always larger than the correct one by 32.
+ */
+#define __hisi_161601_read_reg(reg) ({ \
+ u64 _old, _new; \
+ int _retries = 200; \
+ \
+ do { \
+ _old = read_sysreg(reg); \
+ _new = read_sysreg(reg); \
+ _retries--; \
+ } while (unlikely((_new - _old) >> 5) && _retries); \
+ \
+ WARN_ON_ONCE(!_retries); \
+ _new; \
+})
+
#define arch_timer_reg_read_stable(reg) \
({ \
u64 _val; \
if (needs_timer_erratum_workaround()) \
- _val = erratum_workaround->read_##reg(); \
+ _val = erratum_workaround->read_##reg();\
else \
_val = read_sysreg(reg); \
_val; \
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 8a753fd..4aafb6a 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -312,8 +312,20 @@ config FSL_ERRATUM_A008585
help
This option enables a workaround for Freescale/NXP Erratum
A-008585 ("ARM generic timer may contain an erroneous
- value"). The workaround will only be active if the
+ value"). The workaround will be active if the
fsl,erratum-a008585 property is found in the timer node.
+ This can be overridden with the clocksource.arm_arch_timer.fsl-a008585
+ boot parameter.
+
+config HISILICON_ERRATUM_161601
+ bool "Workaround for Hisilicon Erratum 161601"
+ default y
+ depends on ARM_ARCH_TIMER && ARM64
+ help
+ This option enables a workaround for Hisilicon Erratum
+ 161601. The workaround will be active if the hisilicon,erratum-161601
+ property is found in the timer node. This can be overridden with
+ the clocksource.arm_arch_timer.hisilicon-161601 boot parameter.
config ARM_GLOBAL_TIMER
bool "Support for the ARM global timer" if COMPILE_TEST
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index e4f7fa1..89f1895 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -94,13 +94,14 @@ early_param("clocksource.arm_arch_timer.evtstrm", early_evtstrm_cfg);
* Architected system timer support.
*/
-#ifdef CONFIG_FSL_ERRATUM_A008585
+#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585) || IS_ENABLED(CONFIG_HISILICON_ERRATUM_161601)
struct arch_timer_erratum_workaround *erratum_workaround = NULL;
DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
+#endif
-
+#ifdef CONFIG_FSL_ERRATUM_A008585
static u32 fsl_a008585_read_cntp_tval_el0(void)
{
return __fsl_a008585_read_reg(cntp_tval_el0);
@@ -139,6 +140,45 @@ static int __init early_fsl_a008585_cfg(char *buf)
early_param("clocksource.arm_arch_timer.fsl-a008585", early_fsl_a008585_cfg);
#endif /* CONFIG_FSL_ERRATUM_A008585 */
+#ifdef CONFIG_HISILICON_ERRATUM_161601
+static u32 hisi_161601_read_cntp_tval_el0(void)
+{
+ return __hisi_161601_read_reg(cntp_tval_el0);
+}
+
+static u32 hisi_161601_read_cntv_tval_el0(void)
+{
+ return __hisi_161601_read_reg(cntv_tval_el0);
+}
+
+static u64 hisi_161601_read_cntvct_el0(void)
+{
+ return __hisi_161601_read_reg(cntvct_el0);
+}
+
+static struct arch_timer_erratum_workaround arch_timer_hisi_161601 = {
+ .read_cntp_tval_el0 = hisi_161601_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = hisi_161601_read_cntv_tval_el0,
+ .read_cntvct_el0 = hisi_161601_read_cntvct_el0,
+};
+
+static int __init early_hisi_161601_cfg(char *buf)
+{
+ int ret;
+ bool val;
+
+ ret = strtobool(buf, &val);
+ if (ret)
+ return ret;
+
+ if (val)
+ erratum_workaround = &arch_timer_hisi_161601;
+
+ return 0;
+}
+early_param("clocksource.arm_arch_timer.hisilicon-161601", early_hisi_161601_cfg);
+#endif /* CONFIG_HISILICON_ERRATUM_161601 */
+
static __always_inline
void arch_timer_reg_write(int access, enum arch_timer_reg reg, u32 val,
struct clock_event_device *clk)
@@ -288,8 +328,8 @@ static __always_inline void set_next_event(const int access, unsigned long evt,
arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
}
-#ifdef CONFIG_FSL_ERRATUM_A008585
-static __always_inline void fsl_a008585_set_next_event(const int access,
+#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585) || IS_ENABLED(CONFIG_HISILICON_ERRATUM_161601)
+static __always_inline void erratum_set_next_event(const int access,
unsigned long evt, struct clock_event_device *clk)
{
unsigned long ctrl;
@@ -307,20 +347,20 @@ static __always_inline void fsl_a008585_set_next_event(const int access,
arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
}
-static int fsl_a008585_set_next_event_virt(unsigned long evt,
+static int erratum_set_next_event_virt(unsigned long evt,
struct clock_event_device *clk)
{
- fsl_a008585_set_next_event(ARCH_TIMER_VIRT_ACCESS, evt, clk);
+ erratum_set_next_event(ARCH_TIMER_VIRT_ACCESS, evt, clk);
return 0;
}
-static int fsl_a008585_set_next_event_phys(unsigned long evt,
+static int erratum_set_next_event_phys(unsigned long evt,
struct clock_event_device *clk)
{
- fsl_a008585_set_next_event(ARCH_TIMER_PHYS_ACCESS, evt, clk);
+ erratum_set_next_event(ARCH_TIMER_PHYS_ACCESS, evt, clk);
return 0;
}
-#endif /* CONFIG_FSL_ERRATUM_A008585 */
+#endif
static int arch_timer_set_next_event_virt(unsigned long evt,
struct clock_event_device *clk)
@@ -350,16 +390,16 @@ static int arch_timer_set_next_event_phys_mem(unsigned long evt,
return 0;
}
-static void fsl_a008585_set_sne(struct clock_event_device *clk)
+static void erratum_set_sne(struct clock_event_device *clk)
{
-#ifdef CONFIG_FSL_ERRATUM_A008585
+#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585) || IS_ENABLED(CONFIG_HISILICON_ERRATUM_161601)
if (!static_branch_unlikely(&arch_timer_read_ool_enabled))
return;
if (arch_timer_uses_ppi == VIRT_PPI)
- clk->set_next_event = fsl_a008585_set_next_event_virt;
+ clk->set_next_event = erratum_set_next_event_virt;
else
- clk->set_next_event = fsl_a008585_set_next_event_phys;
+ clk->set_next_event = erratum_set_next_event_phys;
#endif
}
@@ -392,7 +432,7 @@ static void __arch_timer_setup(unsigned type,
BUG();
}
- fsl_a008585_set_sne(clk);
+ erratum_set_sne(clk);
} else {
clk->features |= CLOCK_EVT_FEAT_DYNIRQ;
clk->name = "arch_mem_timer";
@@ -612,7 +652,7 @@ static void __init arch_counter_register(unsigned type)
clocksource_counter.archdata.vdso_direct = true;
-#ifdef CONFIG_FSL_ERRATUM_A008585
+#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585) || IS_ENABLED(CONFIG_HISILICON_ERRATUM_161601)
/*
* Don't use the vdso fastpath if errata require using
* the out-of-line counter accessor.
@@ -899,12 +939,22 @@ static int __init arch_timer_of_init(struct device_node *np)
arch_timer_c3stop = !of_property_read_bool(np, "always-on");
#ifdef CONFIG_FSL_ERRATUM_A008585
- if (!erratum_workaround && of_property_read_bool(np, "fsl,erratum-a008585"))
+ if (!erratum_workaround && of_property_read_bool(np, "fsl,erratum-a008585")) {
erratum_workaround = &arch_timer_fsl_a008585;
+ if (erratum_workaround) {
+ static_branch_enable(&arch_timer_read_ool_enabled);
+ pr_info("Enabling workaround for FSL erratum A-008585\n");
+ }
+ }
+#endif
- if (erratum_workaround) {
- static_branch_enable(&arch_timer_read_ool_enabled);
- pr_info("Enabling workaround for FSL erratum A-008585\n");
+#ifdef CONFIG_HISILICON_ERRATUM_161601
+ if (!erratum_workaround && of_property_read_bool(np, "hisilicon,erratum-161601")) {
+ erratum_workaround = &arch_timer_hisi_161601;
+ if (erratum_workaround) {
+ static_branch_enable(&arch_timer_read_ool_enabled);
+ pr_info("Enabling workaround for HISILICON erratum 161601\n");
+ }
}
#endif
--
1.9.0
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