diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 8ef73e89d514..d89bb22589f6 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -260,14 +260,26 @@ asmlinkage void post_ttbr_update_workaround(void)
 			CONFIG_CAVIUM_ERRATUM_27456));
 }
 
-static int asids_init(void)
+static int asids_update_limit(void)
 {
-	asid_bits = get_cpu_asid_bits();
+	unsigned long num_available_asids = NUM_USER_ASIDS;
+
+	if (arm64_kernel_unmapped_at_el0())
+		num_available_asids /= 2;
 	/*
 	 * Expect allocation after rollover to fail if we don't have at least
 	 * one more ASID than CPUs. ASID #0 is reserved for init_mm.
 	 */
-	WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus());
+	WARN_ON(num_available_asids - 1 <= num_possible_cpus());
+	pr_info("ASID allocator initialised with %lu entries\n",
+		num_available_asids);
+	return 0;
+}
+arch_initcall(asids_update_limit);
+
+static int asids_init(void)
+{
+	asid_bits = get_cpu_asid_bits();
 	atomic64_set(&asid_generation, ASID_FIRST_VERSION);
 	asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), sizeof(*asid_map),
 			   GFP_KERNEL);
@@ -282,8 +294,6 @@ static int asids_init(void)
 	 */
 	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
 		set_kpti_asid_bits();
-
-	pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
 	return 0;
 }
 early_initcall(asids_init);
diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index acce8781c456..f5c7a845cd7b 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -24,8 +24,6 @@ static int arm_pmu_acpi_register_irq(int cpu)
 	int gsi, trigger;
 
 	gicc = acpi_cpu_get_madt_gicc(cpu);
-	if (WARN_ON(!gicc))
-		return -EINVAL;
 
 	gsi = gicc->performance_interrupt;
 
@@ -64,11 +62,10 @@ static void arm_pmu_acpi_unregister_irq(int cpu)
 	int gsi;
 
 	gicc = acpi_cpu_get_madt_gicc(cpu);
-	if (!gicc)
-		return;
 
 	gsi = gicc->performance_interrupt;
-	acpi_unregister_gsi(gsi);
+	if (gsi)
+		acpi_unregister_gsi(gsi);
 }
 
 #if IS_ENABLED(CONFIG_ARM_SPE_PMU)
diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
index 95dca2cb5265..90884d14f95f 100644
--- a/drivers/perf/fsl_imx8_ddr_perf.c
+++ b/drivers/perf/fsl_imx8_ddr_perf.c
@@ -388,9 +388,10 @@ static void ddr_perf_counter_enable(struct ddr_pmu *pmu, int config,
 
 	if (enable) {
 		/*
-		 * must disable first, then enable again
-		 * otherwise, cycle counter will not work
-		 * if previous state is enabled.
+		 * cycle counter is special which should firstly write 0 then
+		 * write 1 into CLEAR bit to clear it. Other counters only
+		 * need write 0 into CLEAR bit and it turns out to be 1 by
+		 * hardware. Below enable flow is harmless for all counters.
 		 */
 		writel(0, pmu->base + reg);
 		val = CNTL_EN | CNTL_CLEAR;
@@ -398,7 +399,8 @@ static void ddr_perf_counter_enable(struct ddr_pmu *pmu, int config,
 		writel(val, pmu->base + reg);
 	} else {
 		/* Disable counter */
-		writel(0, pmu->base + reg);
+		val = readl_relaxed(pmu->base + reg) & CNTL_EN_MASK;
+		writel(val, pmu->base + reg);
 	}
 }