@@ -97,6 +97,7 @@ CONFIG_SPARSEMEM_MANUAL=y
CONFIG_SPARSEMEM_VMEMMAP=y
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
CONFIG_SUN50I_A64_CCU=y
+CONFIG_SUN50I_ERRATUM_UNKNOWN1=y
CONFIG_SYSCTL_EXCEPTION_TRACE=y
CONFIG_THREAD_INFO_IN_TASK=y
CONFIG_UNMAP_KERNEL_AT_EL0=y
@@ -93,6 +93,7 @@ CONFIG_SPARSEMEM_VMEMMAP=y
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
CONFIG_SUN50I_A64_CCU=y
CONFIG_SUN50I_DE2_BUS=y
+CONFIG_SUN50I_ERRATUM_UNKNOWN1=y
CONFIG_SUN50I_H6_CCU=y
CONFIG_SUN50I_H6_R_CCU=y
CONFIG_SWIOTLB=y
new file mode 100644
@@ -0,0 +1,125 @@
+From f2e600c149fda3453344f89c7e9353fe278ebd32 Mon Sep 17 00:00:00 2001
+From: Christoffer Dall <christoffer.dall@linaro.org>
+Date: Wed, 18 Oct 2017 13:06:25 +0200
+Subject: [PATCH] arm64: Implement arch_counter_get_cntpct to read the physical
+ counter
+
+As we are about to use the physical counter on arm64 systems that have
+KVM support, implement arch_counter_get_cntpct() and the associated
+errata workaround functionality for stable timer reads.
+
+Cc: Will Deacon <will.deacon@arm.com>
+Cc: Mark Rutland <mark.rutland@arm.com>
+Acked-by: Catalin Marinas <catalin.marinas@arm.com>
+Acked-by: Marc Zyngier <marc.zyngier@arm.com>
+Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
+---
+ arch/arm64/include/asm/arch_timer.h | 8 +++-----
+ drivers/clocksource/arm_arch_timer.c | 23 +++++++++++++++++++++++
+ 2 files changed, 26 insertions(+), 5 deletions(-)
+
+diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
+index a652ce0a5cb2..04275de614db 100644
+--- a/arch/arm64/include/asm/arch_timer.h
++++ b/arch/arm64/include/asm/arch_timer.h
+@@ -52,6 +52,7 @@ struct arch_timer_erratum_workaround {
+ const char *desc;
+ u32 (*read_cntp_tval_el0)(void);
+ u32 (*read_cntv_tval_el0)(void);
++ u64 (*read_cntpct_el0)(void);
+ u64 (*read_cntvct_el0)(void);
+ int (*set_next_event_phys)(unsigned long, struct clock_event_device *);
+ int (*set_next_event_virt)(unsigned long, struct clock_event_device *);
+@@ -148,11 +149,8 @@ static inline void arch_timer_set_cntkctl(u32 cntkctl)
+
+ static inline u64 arch_counter_get_cntpct(void)
+ {
+- /*
+- * AArch64 kernel and user space mandate the use of CNTVCT.
+- */
+- BUG();
+- return 0;
++ isb();
++ return arch_timer_reg_read_stable(cntpct_el0);
+ }
+
+ static inline u64 arch_counter_get_cntvct(void)
+diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
+index fd4b7f684bd0..ff8f8a177156 100644
+--- a/drivers/clocksource/arm_arch_timer.c
++++ b/drivers/clocksource/arm_arch_timer.c
+@@ -217,6 +217,11 @@ static u32 notrace fsl_a008585_read_cntv_tval_el0(void)
+ return __fsl_a008585_read_reg(cntv_tval_el0);
+ }
+
++static u64 notrace fsl_a008585_read_cntpct_el0(void)
++{
++ return __fsl_a008585_read_reg(cntpct_el0);
++}
++
+ static u64 notrace fsl_a008585_read_cntvct_el0(void)
+ {
+ return __fsl_a008585_read_reg(cntvct_el0);
+@@ -258,6 +263,11 @@ static u32 notrace hisi_161010101_read_cntv_tval_el0(void)
+ return __hisi_161010101_read_reg(cntv_tval_el0);
+ }
+
++static u64 notrace hisi_161010101_read_cntpct_el0(void)
++{
++ return __hisi_161010101_read_reg(cntpct_el0);
++}
++
+ static u64 notrace hisi_161010101_read_cntvct_el0(void)
+ {
+ return __hisi_161010101_read_reg(cntvct_el0);
+@@ -288,6 +298,15 @@ static struct ate_acpi_oem_info hisi_161010101_oem_info[] = {
+ #endif
+
+ #ifdef CONFIG_ARM64_ERRATUM_858921
++static u64 notrace arm64_858921_read_cntpct_el0(void)
++{
++ u64 old, new;
++
++ old = read_sysreg(cntpct_el0);
++ new = read_sysreg(cntpct_el0);
++ return (((old ^ new) >> 32) & 1) ? old : new;
++}
++
+ static u64 notrace arm64_858921_read_cntvct_el0(void)
+ {
+ u64 old, new;
+@@ -346,6 +365,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .desc = "Freescale erratum a005858",
+ .read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
++ .read_cntpct_el0 = fsl_a008585_read_cntpct_el0,
+ .read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
+ .set_next_event_phys = erratum_set_next_event_tval_phys,
+ .set_next_event_virt = erratum_set_next_event_tval_virt,
+@@ -358,6 +378,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .desc = "HiSilicon erratum 161010101",
+ .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
++ .read_cntpct_el0 = hisi_161010101_read_cntpct_el0,
+ .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
+ .set_next_event_phys = erratum_set_next_event_tval_phys,
+ .set_next_event_virt = erratum_set_next_event_tval_virt,
+@@ -368,6 +389,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .desc = "HiSilicon erratum 161010101",
+ .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
++ .read_cntpct_el0 = hisi_161010101_read_cntpct_el0,
+ .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
+ .set_next_event_phys = erratum_set_next_event_tval_phys,
+ .set_next_event_virt = erratum_set_next_event_tval_virt,
+@@ -378,6 +400,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .match_type = ate_match_local_cap_id,
+ .id = (void *)ARM64_WORKAROUND_858921,
+ .desc = "ARM erratum 858921",
++ .read_cntpct_el0 = arm64_858921_read_cntpct_el0,
+ .read_cntvct_el0 = arm64_858921_read_cntvct_el0,
+ },
+ #endif
+--
+2.17.1
+
new file mode 100644
@@ -0,0 +1,528 @@
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+ Sat, 12 Jan 2019 21:17:21 -0500 (EST)
+From: Samuel Holland <samuel@sholland.org>
+To: Catalin Marinas <catalin.marinas@arm.com>,
+ Will Deacon <will.deacon@arm.com>,
+ Maxime Ripard <maxime.ripard@bootlin.com>, Chen-Yu Tsai <wens@csie.org>,
+ Rob Herring <robh+dt@kernel.org>, Mark Rutland <Mark.Rutland@arm.com>,
+ Daniel Lezcano <daniel.lezcano@linaro.org>,
+ Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <marc.zyngier@arm.com>
+Subject: [PATCH v3 1/2] arm64: arch_timer: Workaround for Allwinner A64 timer
+ instability
+Date: Sat, 12 Jan 2019 20:17:18 -0600
+Message-Id: <20190113021719.46457-2-samuel@sholland.org>
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+
+The Allwinner A64 SoC is known[1] to have an unstable architectural
+timer, which manifests itself most obviously in the time jumping forward
+a multiple of 95 years[2][3]. This coincides with 2^56 cycles at a
+timer frequency of 24 MHz, implying that the time went slightly backward
+(and this was interpreted by the kernel as it jumping forward and
+wrapping around past the epoch).
+
+Investigation revealed instability in the low bits of CNTVCT at the
+point a high bit rolls over. This leads to power-of-two cycle forward
+and backward jumps. (Testing shows that forward jumps are about twice as
+likely as backward jumps.) Since the counter value returns to normal
+after an indeterminate read, each "jump" really consists of both a
+forward and backward jump from the software perspective.
+
+Unless the kernel is trapping CNTVCT reads, a userspace program is able
+to read the register in a loop faster than it changes. A test program
+running on all 4 CPU cores that reported jumps larger than 100 ms was
+run for 13.6 hours and reported the following:
+
+ Count | Event
+-------+---------------------------
+ 9940 | jumped backward 699ms
+ 268 | jumped backward 1398ms
+ 1 | jumped backward 2097ms
+ 16020 | jumped forward 175ms
+ 6443 | jumped forward 699ms
+ 2976 | jumped forward 1398ms
+ 9 | jumped forward 356516ms
+ 9 | jumped forward 357215ms
+ 4 | jumped forward 714430ms
+ 1 | jumped forward 3578440ms
+
+This works out to a jump larger than 100 ms about every 5.5 seconds on
+each CPU core.
+
+The largest jump (almost an hour!) was the following sequence of reads:
+ 0x0000007fffffffff → 0x00000093feffffff → 0x0000008000000000
+
+Note that the middle bits don't necessarily all read as all zeroes or
+all ones during the anomalous behavior; however the low 10 bits checked
+by the function in this patch have never been observed with any other
+value.
+
+Also note that smaller jumps are much more common, with backward jumps
+of 2048 (2^11) cycles observed over 400 times per second on each core.
+(Of course, this is partially explained by lower bits rolling over more
+frequently.) Any one of these could have caused the 95 year time skip.
+
+Similar anomalies were observed while reading CNTPCT (after patching the
+kernel to allow reads from userspace). However, the CNTPCT jumps are
+much less frequent, and only small jumps were observed. The same program
+as before (except now reading CNTPCT) observed after 72 hours:
+
+ Count | Event
+-------+---------------------------
+ 17 | jumped backward 699ms
+ 52 | jumped forward 175ms
+ 2831 | jumped forward 699ms
+ 5 | jumped forward 1398ms
+
+Further investigation showed that the instability in CNTPCT/CNTVCT also
+affected the respective timer's TVAL register. The following values were
+observed immediately after writing CNVT_TVAL to 0x10000000:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL | CNTV_TVAL Error
+--------------------+------------+--------------------+-----------------
+ 0x000000d4a2d8bfff | 0x10003fff | 0x000000d4b2d8bfff | +0x00004000
+ 0x000000d4a2d94000 | 0x0fffffff | 0x000000d4b2d97fff | -0x00004000
+ 0x000000d4a2d97fff | 0x10003fff | 0x000000d4b2d97fff | +0x00004000
+ 0x000000d4a2d9c000 | 0x0fffffff | 0x000000d4b2d9ffff | -0x00004000
+
+The pattern of errors in CNTV_TVAL seemed to depend on exactly which
+value was written to it. For example, after writing 0x10101010:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL | CNTV_TVAL Error
+--------------------+------------+--------------------+-----------------
+ 0x000001ac3effffff | 0x1110100f | 0x000001ac4f10100f | +0x1000000
+ 0x000001ac40000000 | 0x1010100f | 0x000001ac5110100f | -0x1000000
+ 0x000001ac58ffffff | 0x1110100f | 0x000001ac6910100f | +0x1000000
+ 0x000001ac66000000 | 0x1010100f | 0x000001ac7710100f | -0x1000000
+ 0x000001ac6affffff | 0x1110100f | 0x000001ac7b10100f | +0x1000000
+ 0x000001ac6e000000 | 0x1010100f | 0x000001ac7f10100f | -0x1000000
+
+I was also twice able to reproduce the issue covered by Allwinner's
+workaround[4], that writing to TVAL sometimes fails, and both CVAL and
+TVAL are left with entirely bogus values. One was the following values:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL
+--------------------+------------+--------------------------------------
+ 0x000000d4a2d6014c | 0x8fbd5721 | 0x000000d132935fff (615s in the past)
+Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
+
+========================================================================
+
+Because the CPU can read the CNTPCT/CNTVCT registers faster than they
+change, performing two reads of the register and comparing the high bits
+(like other workarounds) is not a workable solution. And because the
+timer can jump both forward and backward, no pair of reads can
+distinguish a good value from a bad one. The only way to guarantee a
+good value from consecutive reads would be to read _three_ times, and
+take the middle value only if the three values are 1) each unique and
+2) increasing. This takes at minimum 3 counter cycles (125 ns), or more
+if an anomaly is detected.
+
+However, since there is a distinct pattern to the bad values, we can
+optimize the common case (1022/1024 of the time) to a single read by
+simply ignoring values that match the error pattern. This still takes no
+more than 3 cycles in the worst case, and requires much less code. As an
+additional safety check, we still limit the loop iteration to the number
+of max-frequency (1.2 GHz) CPU cycles in three 24 MHz counter periods.
+
+For the TVAL registers, the simple solution is to not use them. Instead,
+read or write the CVAL and calculate the TVAL value in software.
+
+Although the manufacturer is aware of at least part of the erratum[4],
+there is no official name for it. For now, use the kernel-internal name
+"UNKNOWN1".
+
+[1]: https://github.com/armbian/build/commit/a08cd6fe7ae9
+[2]: https://forum.armbian.com/topic/3458-a64-datetime-clock-issue/
+[3]: https://irclog.whitequark.org/linux-sunxi/2018-01-26
+[4]: https://github.com/Allwinner-Homlet/H6-BSP4.9-linux/blob/master/drivers/clocksource/arm_arch_timer.c#L272
+
+Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
+Tested-by: Andre Przywara <andre.przywara@arm.com>
+Signed-off-by: Samuel Holland <samuel@sholland.org>
+---
+ Documentation/arm64/silicon-errata.txt | 2 +
+ drivers/clocksource/Kconfig | 10 +++++
+ drivers/clocksource/arm_arch_timer.c | 55 ++++++++++++++++++++++++++
+ 3 files changed, 67 insertions(+)
+
+diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
+index 8f9577621144..4a269732d2a0 100644
+--- a/Documentation/arm64/silicon-errata.txt
++++ b/Documentation/arm64/silicon-errata.txt
+@@ -44,6 +44,8 @@ stable kernels.
+
+ | Implementor | Component | Erratum ID | Kconfig |
+ +----------------+-----------------+-----------------+-----------------------------+
++| Allwinner | A64/R18 | UNKNOWN1 | SUN50I_ERRATUM_UNKNOWN1 |
++| | | | |
+ | ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+ | ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+ | ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
+index 55c77e44bb2d..d20ff4da07c3 100644
+--- a/drivers/clocksource/Kconfig
++++ b/drivers/clocksource/Kconfig
+@@ -374,6 +374,16 @@ config ARM64_ERRATUM_858921
+ The workaround will be dynamically enabled when an affected
+ core is detected.
+
++config SUN50I_ERRATUM_UNKNOWN1
++ bool "Workaround for Allwinner A64 erratum UNKNOWN1"
++ default y
++ depends on ARM_ARCH_TIMER && ARM64 && ARCH_SUNXI
++ select ARM_ARCH_TIMER_OOL_WORKAROUND
++ help
++ This option enables a workaround for instability in the timer on
++ the Allwinner A64 SoC. The workaround will only be active if the
++ allwinner,erratum-unknown1 property is found in the timer node.
++
+ config ARM_GLOBAL_TIMER
+ bool "Support for the ARM global timer" if COMPILE_TEST
+ select TIMER_OF if OF
+diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
+index 9a7d4dc00b6e..a8b20b65bd4b 100644
+--- a/drivers/clocksource/arm_arch_timer.c
++++ b/drivers/clocksource/arm_arch_timer.c
+@@ -317,6 +317,48 @@ static u64 notrace arm64_1188873_read_cntvct_el0(void)
+ }
+ #endif
+
++#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
++/*
++ * The low bits of the counter registers are indeterminate while bit 10 or
++ * greater is rolling over. Since the counter value can jump both backward
++ * (7ff -> 000 -> 800) and forward (7ff -> fff -> 800), ignore register values
++ * with all ones or all zeros in the low bits. Bound the loop by the maximum
++ * number of CPU cycles in 3 consecutive 24 MHz counter periods.
++ */
++#define __sun50i_a64_read_reg(reg) ({ \
++ u64 _val; \
++ int _retries = 150; \
++ \
++ do { \
++ _val = read_sysreg(reg); \
++ _retries--; \
++ } while (((_val + 1) & GENMASK(9, 0)) <= 1 && _retries); \
++ \
++ WARN_ON_ONCE(!_retries); \
++ _val; \
++})
++
++static u64 notrace sun50i_a64_read_cntpct_el0(void)
++{
++ return __sun50i_a64_read_reg(cntpct_el0);
++}
++
++static u64 notrace sun50i_a64_read_cntvct_el0(void)
++{
++ return __sun50i_a64_read_reg(cntvct_el0);
++}
++
++static u32 notrace sun50i_a64_read_cntp_tval_el0(void)
++{
++ return read_sysreg(cntp_cval_el0) - sun50i_a64_read_cntpct_el0();
++}
++
++static u32 notrace sun50i_a64_read_cntv_tval_el0(void)
++{
++ return read_sysreg(cntv_cval_el0) - sun50i_a64_read_cntvct_el0();
++}
++#endif
++
+ #ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
+ DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
+ timer_unstable_counter_workaround);
+@@ -404,6 +404,19 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .read_cntvct_el0 = arm64_858921_read_cntvct_el0,
+ },
+ #endif
++#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
++ {
++ .match_type = ate_match_dt,
++ .id = "allwinner,erratum-unknown1",
++ .desc = "Allwinner erratum UNKNOWN1",
++ .read_cntp_tval_el0 = sun50i_a64_read_cntp_tval_el0,
++ .read_cntv_tval_el0 = sun50i_a64_read_cntv_tval_el0,
++ .read_cntpct_el0 = sun50i_a64_read_cntpct_el0,
++ .read_cntvct_el0 = sun50i_a64_read_cntvct_el0,
++ .set_next_event_phys = erratum_set_next_event_tval_phys,
++ .set_next_event_virt = erratum_set_next_event_tval_virt,
++ },
++#endif
+ };
+
+ typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
+
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+ Sat, 12 Jan 2019 21:17:22 -0500 (EST)
+From: Samuel Holland <samuel@sholland.org>
+To: Catalin Marinas <catalin.marinas@arm.com>,
+ Will Deacon <will.deacon@arm.com>,
+ Maxime Ripard <maxime.ripard@bootlin.com>, Chen-Yu Tsai <wens@csie.org>,
+ Rob Herring <robh+dt@kernel.org>, Mark Rutland <Mark.Rutland@arm.com>,
+ Daniel Lezcano <daniel.lezcano@linaro.org>,
+ Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <marc.zyngier@arm.com>
+Subject: [PATCH v3 2/2] arm64: dts: allwinner: a64: Enable A64 timer
+ workaround
+Date: Sat, 12 Jan 2019 20:17:19 -0600
+Message-Id: <20190113021719.46457-3-samuel@sholland.org>
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+Cc: devicetree@vger.kernel.org, linux-sunxi@googlegroups.com,
+ linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
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+
+As instability in the architectural timer has been observed on multiple
+devices using this SoC, inluding the Pine64 and the Orange Pi Win,
+enable the workaround in the SoC's device tree.
+
+Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
+Signed-off-by: Samuel Holland <samuel@sholland.org>
+---
+ arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
+index f3a66f888205..13eac92a8c55 100644
+--- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
++++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
+@@ -114,6 +114,7 @@
+
+ timer {
+ compatible = "arm,armv8-timer";
++ allwinner,erratum-unknown1;
+ interrupts = <GIC_PPI 13
+ (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_HIGH)>,
+ <GIC_PPI 14
new file mode 100644
@@ -0,0 +1,528 @@
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+ Sat, 12 Jan 2019 21:17:21 -0500 (EST)
+From: Samuel Holland <samuel@sholland.org>
+To: Catalin Marinas <catalin.marinas@arm.com>,
+ Will Deacon <will.deacon@arm.com>,
+ Maxime Ripard <maxime.ripard@bootlin.com>, Chen-Yu Tsai <wens@csie.org>,
+ Rob Herring <robh+dt@kernel.org>, Mark Rutland <Mark.Rutland@arm.com>,
+ Daniel Lezcano <daniel.lezcano@linaro.org>,
+ Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <marc.zyngier@arm.com>
+Subject: [PATCH v3 1/2] arm64: arch_timer: Workaround for Allwinner A64 timer
+ instability
+Date: Sat, 12 Jan 2019 20:17:18 -0600
+Message-Id: <20190113021719.46457-2-samuel@sholland.org>
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+
+The Allwinner A64 SoC is known[1] to have an unstable architectural
+timer, which manifests itself most obviously in the time jumping forward
+a multiple of 95 years[2][3]. This coincides with 2^56 cycles at a
+timer frequency of 24 MHz, implying that the time went slightly backward
+(and this was interpreted by the kernel as it jumping forward and
+wrapping around past the epoch).
+
+Investigation revealed instability in the low bits of CNTVCT at the
+point a high bit rolls over. This leads to power-of-two cycle forward
+and backward jumps. (Testing shows that forward jumps are about twice as
+likely as backward jumps.) Since the counter value returns to normal
+after an indeterminate read, each "jump" really consists of both a
+forward and backward jump from the software perspective.
+
+Unless the kernel is trapping CNTVCT reads, a userspace program is able
+to read the register in a loop faster than it changes. A test program
+running on all 4 CPU cores that reported jumps larger than 100 ms was
+run for 13.6 hours and reported the following:
+
+ Count | Event
+-------+---------------------------
+ 9940 | jumped backward 699ms
+ 268 | jumped backward 1398ms
+ 1 | jumped backward 2097ms
+ 16020 | jumped forward 175ms
+ 6443 | jumped forward 699ms
+ 2976 | jumped forward 1398ms
+ 9 | jumped forward 356516ms
+ 9 | jumped forward 357215ms
+ 4 | jumped forward 714430ms
+ 1 | jumped forward 3578440ms
+
+This works out to a jump larger than 100 ms about every 5.5 seconds on
+each CPU core.
+
+The largest jump (almost an hour!) was the following sequence of reads:
+ 0x0000007fffffffff → 0x00000093feffffff → 0x0000008000000000
+
+Note that the middle bits don't necessarily all read as all zeroes or
+all ones during the anomalous behavior; however the low 10 bits checked
+by the function in this patch have never been observed with any other
+value.
+
+Also note that smaller jumps are much more common, with backward jumps
+of 2048 (2^11) cycles observed over 400 times per second on each core.
+(Of course, this is partially explained by lower bits rolling over more
+frequently.) Any one of these could have caused the 95 year time skip.
+
+Similar anomalies were observed while reading CNTPCT (after patching the
+kernel to allow reads from userspace). However, the CNTPCT jumps are
+much less frequent, and only small jumps were observed. The same program
+as before (except now reading CNTPCT) observed after 72 hours:
+
+ Count | Event
+-------+---------------------------
+ 17 | jumped backward 699ms
+ 52 | jumped forward 175ms
+ 2831 | jumped forward 699ms
+ 5 | jumped forward 1398ms
+
+Further investigation showed that the instability in CNTPCT/CNTVCT also
+affected the respective timer's TVAL register. The following values were
+observed immediately after writing CNVT_TVAL to 0x10000000:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL | CNTV_TVAL Error
+--------------------+------------+--------------------+-----------------
+ 0x000000d4a2d8bfff | 0x10003fff | 0x000000d4b2d8bfff | +0x00004000
+ 0x000000d4a2d94000 | 0x0fffffff | 0x000000d4b2d97fff | -0x00004000
+ 0x000000d4a2d97fff | 0x10003fff | 0x000000d4b2d97fff | +0x00004000
+ 0x000000d4a2d9c000 | 0x0fffffff | 0x000000d4b2d9ffff | -0x00004000
+
+The pattern of errors in CNTV_TVAL seemed to depend on exactly which
+value was written to it. For example, after writing 0x10101010:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL | CNTV_TVAL Error
+--------------------+------------+--------------------+-----------------
+ 0x000001ac3effffff | 0x1110100f | 0x000001ac4f10100f | +0x1000000
+ 0x000001ac40000000 | 0x1010100f | 0x000001ac5110100f | -0x1000000
+ 0x000001ac58ffffff | 0x1110100f | 0x000001ac6910100f | +0x1000000
+ 0x000001ac66000000 | 0x1010100f | 0x000001ac7710100f | -0x1000000
+ 0x000001ac6affffff | 0x1110100f | 0x000001ac7b10100f | +0x1000000
+ 0x000001ac6e000000 | 0x1010100f | 0x000001ac7f10100f | -0x1000000
+
+I was also twice able to reproduce the issue covered by Allwinner's
+workaround[4], that writing to TVAL sometimes fails, and both CVAL and
+TVAL are left with entirely bogus values. One was the following values:
+
+ CNTVCT | CNTV_TVAL | CNTV_CVAL
+--------------------+------------+--------------------------------------
+ 0x000000d4a2d6014c | 0x8fbd5721 | 0x000000d132935fff (615s in the past)
+Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
+
+========================================================================
+
+Because the CPU can read the CNTPCT/CNTVCT registers faster than they
+change, performing two reads of the register and comparing the high bits
+(like other workarounds) is not a workable solution. And because the
+timer can jump both forward and backward, no pair of reads can
+distinguish a good value from a bad one. The only way to guarantee a
+good value from consecutive reads would be to read _three_ times, and
+take the middle value only if the three values are 1) each unique and
+2) increasing. This takes at minimum 3 counter cycles (125 ns), or more
+if an anomaly is detected.
+
+However, since there is a distinct pattern to the bad values, we can
+optimize the common case (1022/1024 of the time) to a single read by
+simply ignoring values that match the error pattern. This still takes no
+more than 3 cycles in the worst case, and requires much less code. As an
+additional safety check, we still limit the loop iteration to the number
+of max-frequency (1.2 GHz) CPU cycles in three 24 MHz counter periods.
+
+For the TVAL registers, the simple solution is to not use them. Instead,
+read or write the CVAL and calculate the TVAL value in software.
+
+Although the manufacturer is aware of at least part of the erratum[4],
+there is no official name for it. For now, use the kernel-internal name
+"UNKNOWN1".
+
+[1]: https://github.com/armbian/build/commit/a08cd6fe7ae9
+[2]: https://forum.armbian.com/topic/3458-a64-datetime-clock-issue/
+[3]: https://irclog.whitequark.org/linux-sunxi/2018-01-26
+[4]: https://github.com/Allwinner-Homlet/H6-BSP4.9-linux/blob/master/drivers/clocksource/arm_arch_timer.c#L272
+
+Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
+Tested-by: Andre Przywara <andre.przywara@arm.com>
+Signed-off-by: Samuel Holland <samuel@sholland.org>
+---
+ Documentation/arm64/silicon-errata.txt | 2 +
+ drivers/clocksource/Kconfig | 10 +++++
+ drivers/clocksource/arm_arch_timer.c | 55 ++++++++++++++++++++++++++
+ 3 files changed, 67 insertions(+)
+
+diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
+index 8f9577621144..4a269732d2a0 100644
+--- a/Documentation/arm64/silicon-errata.txt
++++ b/Documentation/arm64/silicon-errata.txt
+@@ -44,6 +44,8 @@ stable kernels.
+
+ | Implementor | Component | Erratum ID | Kconfig |
+ +----------------+-----------------+-----------------+-----------------------------+
++| Allwinner | A64/R18 | UNKNOWN1 | SUN50I_ERRATUM_UNKNOWN1 |
++| | | | |
+ | ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+ | ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+ | ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
+index 55c77e44bb2d..d20ff4da07c3 100644
+--- a/drivers/clocksource/Kconfig
++++ b/drivers/clocksource/Kconfig
+@@ -365,6 +365,16 @@ config ARM64_ERRATUM_858921
+ The workaround will be dynamically enabled when an affected
+ core is detected.
+
++config SUN50I_ERRATUM_UNKNOWN1
++ bool "Workaround for Allwinner A64 erratum UNKNOWN1"
++ default y
++ depends on ARM_ARCH_TIMER && ARM64 && ARCH_SUNXI
++ select ARM_ARCH_TIMER_OOL_WORKAROUND
++ help
++ This option enables a workaround for instability in the timer on
++ the Allwinner A64 SoC. The workaround will only be active if the
++ allwinner,erratum-unknown1 property is found in the timer node.
++
+ config ARM_GLOBAL_TIMER
+ bool "Support for the ARM global timer" if COMPILE_TEST
+ select TIMER_OF if OF
+diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
+index 9a7d4dc00b6e..a8b20b65bd4b 100644
+--- a/drivers/clocksource/arm_arch_timer.c
++++ b/drivers/clocksource/arm_arch_timer.c
+@@ -319,6 +319,48 @@ static u64 notrace arm64_1188873_read_cntvct_el0(void)
+ }
+ #endif
+
++#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
++/*
++ * The low bits of the counter registers are indeterminate while bit 10 or
++ * greater is rolling over. Since the counter value can jump both backward
++ * (7ff -> 000 -> 800) and forward (7ff -> fff -> 800), ignore register values
++ * with all ones or all zeros in the low bits. Bound the loop by the maximum
++ * number of CPU cycles in 3 consecutive 24 MHz counter periods.
++ */
++#define __sun50i_a64_read_reg(reg) ({ \
++ u64 _val; \
++ int _retries = 150; \
++ \
++ do { \
++ _val = read_sysreg(reg); \
++ _retries--; \
++ } while (((_val + 1) & GENMASK(9, 0)) <= 1 && _retries); \
++ \
++ WARN_ON_ONCE(!_retries); \
++ _val; \
++})
++
++static u64 notrace sun50i_a64_read_cntpct_el0(void)
++{
++ return __sun50i_a64_read_reg(cntpct_el0);
++}
++
++static u64 notrace sun50i_a64_read_cntvct_el0(void)
++{
++ return __sun50i_a64_read_reg(cntvct_el0);
++}
++
++static u32 notrace sun50i_a64_read_cntp_tval_el0(void)
++{
++ return read_sysreg(cntp_cval_el0) - sun50i_a64_read_cntpct_el0();
++}
++
++static u32 notrace sun50i_a64_read_cntv_tval_el0(void)
++{
++ return read_sysreg(cntv_cval_el0) - sun50i_a64_read_cntvct_el0();
++}
++#endif
++
+ #ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
+ DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *, timer_unstable_counter_workaround);
+ EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
+@@ -408,6 +408,19 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
+ .read_cntvct_el0 = arm64_858921_read_cntvct_el0,
+ },
+ #endif
++#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
++ {
++ .match_type = ate_match_dt,
++ .id = "allwinner,erratum-unknown1",
++ .desc = "Allwinner erratum UNKNOWN1",
++ .read_cntp_tval_el0 = sun50i_a64_read_cntp_tval_el0,
++ .read_cntv_tval_el0 = sun50i_a64_read_cntv_tval_el0,
++ .read_cntpct_el0 = sun50i_a64_read_cntpct_el0,
++ .read_cntvct_el0 = sun50i_a64_read_cntvct_el0,
++ .set_next_event_phys = erratum_set_next_event_tval_phys,
++ .set_next_event_virt = erratum_set_next_event_tval_virt,
++ },
++#endif
+ };
+
+ typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
+
+From patchwork Sun Jan 13 02:17:19 2019
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+ Sat, 12 Jan 2019 21:17:22 -0500 (EST)
+From: Samuel Holland <samuel@sholland.org>
+To: Catalin Marinas <catalin.marinas@arm.com>,
+ Will Deacon <will.deacon@arm.com>,
+ Maxime Ripard <maxime.ripard@bootlin.com>, Chen-Yu Tsai <wens@csie.org>,
+ Rob Herring <robh+dt@kernel.org>, Mark Rutland <Mark.Rutland@arm.com>,
+ Daniel Lezcano <daniel.lezcano@linaro.org>,
+ Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <marc.zyngier@arm.com>
+Subject: [PATCH v3 2/2] arm64: dts: allwinner: a64: Enable A64 timer
+ workaround
+Date: Sat, 12 Jan 2019 20:17:19 -0600
+Message-Id: <20190113021719.46457-3-samuel@sholland.org>
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+As instability in the architectural timer has been observed on multiple
+devices using this SoC, inluding the Pine64 and the Orange Pi Win,
+enable the workaround in the SoC's device tree.
+
+Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
+Signed-off-by: Samuel Holland <samuel@sholland.org>
+---
+ arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
+index f3a66f888205..13eac92a8c55 100644
+--- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
++++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
+@@ -159,6 +159,7 @@
+
+ timer {
+ compatible = "arm,armv8-timer";
++ allwinner,erratum-unknown1;
+ interrupts = <GIC_PPI 13
+ (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_HIGH)>,
+ <GIC_PPI 14
Backport A64 unstable timer patches from linux 5.1 Signed-off-by: Oskari Lemmela <oskari@lemmela.net> --- target/linux/sunxi/cortexa53/config-4.14 | 1 + target/linux/sunxi/cortexa53/config-4.19 | 1 + ...arch_counter_get_cntpct-to-read-the-.patch | 125 +++++ ...-for-Allwinner-A64-timer-instability.patch | 528 ++++++++++++++++++ ...-for-Allwinner-A64-timer-instability.patch | 528 ++++++++++++++++++ 5 files changed, 1183 insertions(+) create mode 100644 target/linux/sunxi/patches-4.14/031-arm64-Implement-arch_counter_get_cntpct-to-read-the-.patch create mode 100644 target/linux/sunxi/patches-4.14/100-arm64-arch_timer-Workaround-for-Allwinner-A64-timer-instability.patch create mode 100644 target/linux/sunxi/patches-4.19/100-arm64-arch_timer-Workaround-for-Allwinner-A64-timer-instability.patch