[PATCH v6 2/4] arm64: arch_timer: Introduce a generic erratum handing mechanism for fsl-a008585
Ding Tianhong
dingtianhong at huawei.com
Wed Jan 4 21:31:55 PST 2017
The workaround for hisilicon,161601 will check the return value of the system counter
by different way, in order to distinguish with the fsl-a008585 workaround, introduce
a new generic erratum handing mechanism for fsl-a008585 and rename some functions.
v2: Introducing a new generic erratum handling mechanism for fsl erratum a008585.
v3: Introducing the erratum_workaround_set_sne generic function for fsl erratum a008585
and make the #define __fsl_a008585_read_reg to be private to the .c file instead of
being globally visible. After discussion with Marc and Will, a consensus decision was
made to remove the commandline parameter for enabling fsl,erratum-a008585 erratum,
and make some generic name more specific, export timer_unstable_counter_workaround
for module access.
v5: Adapt the new documentation for kernel-parameters.txt.
v6: Mark the fsl_a008585_read_xxx_el0 with notrace, if CONFIG_FUNCTION_GRAPH_TRACER selected,
fsl_a008585_read_xxx_el0 will be related to ftrace_graph_caller which will calling sched_clock
to read system counter again, it will cause the system stall into an endless loop.
Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
---
Documentation/admin-guide/kernel-parameters.txt | 9 ---
arch/arm64/include/asm/arch_timer.h | 36 ++++--------
drivers/clocksource/arm_arch_timer.c | 78 +++++++++++++++----------
3 files changed, 58 insertions(+), 65 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 21e2d88..76437ad 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -539,15 +539,6 @@
loops can be debugged more effectively on production
systems.
- clocksource.arm_arch_timer.fsl-a008585=
- [ARM64]
- Format: <bool>
- Enable/disable the workaround of Freescale/NXP
- erratum A-008585. 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 eaa5bbe..f882c7c 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -31,39 +31,27 @@
#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585)
extern struct static_key_false arch_timer_read_ool_enabled;
-#define needs_fsl_a008585_workaround() \
+#define needs_unstable_timer_counter_workaround() \
static_branch_unlikely(&arch_timer_read_ool_enabled)
#else
-#define needs_fsl_a008585_workaround() false
+#define needs_unstable_timer_counter_workaround() false
#endif
-u32 __fsl_a008585_read_cntp_tval_el0(void);
-u32 __fsl_a008585_read_cntv_tval_el0(void);
-u64 __fsl_a008585_read_cntvct_el0(void);
-/*
- * The number of retries is an arbitrary value well beyond the highest number
- * of iterations the loop has been observed to take.
- */
-#define __fsl_a008585_read_reg(reg) ({ \
- u64 _old, _new; \
- int _retries = 200; \
- \
- do { \
- _old = read_sysreg(reg); \
- _new = read_sysreg(reg); \
- _retries--; \
- } while (unlikely(_old != _new) && _retries); \
- \
- WARN_ON_ONCE(!_retries); \
- _new; \
-})
+struct arch_timer_erratum_workaround {
+ int erratum; /* Indicate the Erratum ID */
+ u32 (*read_cntp_tval_el0)(void);
+ u32 (*read_cntv_tval_el0)(void);
+ u64 (*read_cntvct_el0)(void);
+};
+
+extern struct arch_timer_erratum_workaround *timer_unstable_counter_workaround;
#define arch_timer_reg_read_stable(reg) \
({ \
u64 _val; \
- if (needs_fsl_a008585_workaround()) \
- _val = __fsl_a008585_read_##reg(); \
+ if (needs_unstable_timer_counter_workaround()) \
+ _val = timer_unstable_counter_workaround->read_##reg();\
else \
_val = read_sysreg(reg); \
_val; \
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 02fef68..f9097b6 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -96,40 +96,53 @@ static int __init early_evtstrm_cfg(char *buf)
*/
#ifdef CONFIG_FSL_ERRATUM_A008585
-DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
-EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
-
-static int fsl_a008585_enable = -1;
+struct arch_timer_erratum_workaround *timer_unstable_counter_workaround = NULL;
+EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
-static int __init early_fsl_a008585_cfg(char *buf)
-{
- int ret;
- bool val;
+#define FSL_A008585 0x0001
- ret = strtobool(buf, &val);
- if (ret)
- return ret;
-
- fsl_a008585_enable = val;
- return 0;
-}
-early_param("clocksource.arm_arch_timer.fsl-a008585", early_fsl_a008585_cfg);
+DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
+EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
-u32 __fsl_a008585_read_cntp_tval_el0(void)
+/*
+ * The number of retries is an arbitrary value well beyond the highest number
+ * of iterations the loop has been observed to take.
+ */
+#define __fsl_a008585_read_reg(reg) ({ \
+ u64 _old, _new; \
+ int _retries = 200; \
+ \
+ do { \
+ _old = read_sysreg(reg); \
+ _new = read_sysreg(reg); \
+ _retries--; \
+ } while (unlikely(_old != _new) && _retries); \
+ \
+ WARN_ON_ONCE(!_retries); \
+ _new; \
+})
+
+static u32 notrace fsl_a008585_read_cntp_tval_el0(void)
{
return __fsl_a008585_read_reg(cntp_tval_el0);
}
-u32 __fsl_a008585_read_cntv_tval_el0(void)
+static u32 notrace fsl_a008585_read_cntv_tval_el0(void)
{
return __fsl_a008585_read_reg(cntv_tval_el0);
}
-u64 __fsl_a008585_read_cntvct_el0(void)
+static u64 notrace fsl_a008585_read_cntvct_el0(void)
{
return __fsl_a008585_read_reg(cntvct_el0);
}
-EXPORT_SYMBOL(__fsl_a008585_read_cntvct_el0);
+
+static struct arch_timer_erratum_workaround arch_timer_fsl_a008585 = {
+ .erratum = FSL_A008585,
+ .read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
+ .read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
+};
#endif /* CONFIG_FSL_ERRATUM_A008585 */
static __always_inline
@@ -282,7 +295,7 @@ static __always_inline void set_next_event(const int access, unsigned long evt,
}
#ifdef CONFIG_FSL_ERRATUM_A008585
-static __always_inline void fsl_a008585_set_next_event(const int access,
+static __always_inline void erratum_set_next_event_generic(const int access,
unsigned long evt, struct clock_event_device *clk)
{
unsigned long ctrl;
@@ -300,17 +313,17 @@ 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_generic(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_generic(ARCH_TIMER_PHYS_ACCESS, evt, clk);
return 0;
}
#endif /* CONFIG_FSL_ERRATUM_A008585 */
@@ -343,16 +356,16 @@ 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_workaround_set_sne(struct clock_event_device *clk)
{
#ifdef CONFIG_FSL_ERRATUM_A008585
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
}
@@ -385,7 +398,7 @@ static void __arch_timer_setup(unsigned type,
BUG();
}
- fsl_a008585_set_sne(clk);
+ erratum_workaround_set_sne(clk);
} else {
clk->features |= CLOCK_EVT_FEAT_DYNIRQ;
clk->name = "arch_mem_timer";
@@ -894,9 +907,10 @@ 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 (fsl_a008585_enable < 0)
- fsl_a008585_enable = of_property_read_bool(np, "fsl,erratum-a008585");
- if (fsl_a008585_enable) {
+ if (!timer_unstable_counter_workaround && of_property_read_bool(np, "fsl,erratum-a008585"))
+ timer_unstable_counter_workaround = &arch_timer_fsl_a008585;
+
+ if (timer_unstable_counter_workaround) {
static_branch_enable(&arch_timer_read_ool_enabled);
pr_info("Enabling workaround for FSL erratum A-008585\n");
}
--
1.9.0
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