[PATCH 4/7] arm64: arch_timer: introduce generic errata handling infrastructure

Mark Rutland
2017-01-31T12:22:34Z

From: Ding Tianhong <dingtianhong@huawei.com>

Currently we have code inline in the arch timer probe path to cater for
Freescale erratum A-008585, complete with ifdeffery. This is a little
ugly, and will get worse as we try to add more errata handling.

This patch refactors the handling of Freescale erratum A-008585. Now the
erratum is described in a generic arch_timer_erratum_workaround
structure, and the probe path can iterate over these to detect errata
and enable workarounds.

This will simplify the addition and maintenance of code handling
Hisilicon erratum 161010101.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
[Mark: split patch, correct Kconfig, reword commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
---
arch/arm64/include/asm/arch_timer.h | 38 +++++----------
drivers/clocksource/Kconfig | 4 ++
drivers/clocksource/arm_arch_timer.c | 92 ++++++++++++++++++++++++------------
3 files changed, 80 insertions(+), 54 deletions(-)

diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index eaa5bbe..b4b3400 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -29,41 +29,29 @@

#include <clocksource/arm_arch_timer.h>

-#if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585)
+#if IS_ENABLED(CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND)
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 {
+ const char *id; /* Indicate the Erratum ID */
+ u32 (*read_cntp_tval_el0)(void);
+ u32 (*read_cntv_tval_el0)(void);
+ u64 (*read_cntvct_el0)(void);
+};
+
+extern const 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/Kconfig b/drivers/clocksource/Kconfig
index 4866f7a..e132bb3 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -325,10 +325,14 @@ config ARM_ARCH_TIMER_EVTSTREAM
This must be disabled for hardware validation purposes to detect any
hardware anomalies of missing events.

+config ARM_ARCH_TIMER_OOL_WORKAROUND
+ bool
+
config FSL_ERRATUM_A008585
bool "Workaround for Freescale/NXP Erratum A-008585"
default y
depends on ARM_ARCH_TIMER && ARM64
+ select ARM_ARCH_TIMER_OOL_WORKAROUND
help
This option enables a workaround for Freescale/NXP Erratum
A-008585 ("ARM generic timer may contain an erroneous
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 6a9d031..2af0739 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -96,27 +96,58 @@ 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;
-
-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);
-#endif /* CONFIG_FSL_ERRATUM_A008585 */
+#endif
+
+#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
+const struct arch_timer_erratum_workaround *timer_unstable_counter_workaround = NULL;
+EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
+
+DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
+EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
+
+static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+#ifdef CONFIG_FSL_ERRATUM_A008585
+ {
+ .id = "fsl,erratum-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
+};
+#endif /* CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND */

static __always_inline
void arch_timer_reg_write(int access, enum arch_timer_reg reg, u32 val,
@@ -267,8 +298,8 @@ 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,
+#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
+static __always_inline void erratum_set_next_event_generic(const int access,
unsigned long evt, struct clock_event_device *clk)
{
unsigned long ctrl;
@@ -286,20 +317,20 @@ 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_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 */
+#endif /* CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND */

static int arch_timer_set_next_event_virt(unsigned long evt,
struct clock_event_device *clk)
@@ -329,16 +360,16 @@ 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
+#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
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
}

@@ -371,7 +402,7 @@ 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";
@@ -591,7 +622,7 @@ static void __init arch_counter_register(unsigned type)

clocksource_counter.archdata.vdso_direct = true;

-#ifdef CONFIG_FSL_ERRATUM_A008585
+#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
/*
* Don't use the vdso fastpath if errata require using
* the out-of-line counter accessor.
@@ -879,12 +910,15 @@ 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) {
- static_branch_enable(&arch_timer_read_ool_enabled);
- pr_info("Enabling workaround for FSL erratum A-008585\n");
+#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
+ for (i = 0; i < ARRAY_SIZE(ool_workarounds); i++) {
+ if (of_property_read_bool(np, ool_workarounds[i].id)) {
+ timer_unstable_counter_workaround = &ool_workarounds[i];
+ static_branch_enable(&arch_timer_read_ool_enabled);
+ pr_info("arch_timer: Enabling workaround for %s\n",
+ timer_unstable_counter_workaround->id);
+ break;
+ }
}
#endif

--
1.9.1