[PATCH 01/12] parisc: Switch from GENERIC_CPU_DEVICES to GENERIC_ARCH_TOPOLOGY

[PATCH 01/12] parisc: Switch from GENERIC_CPU_DEVICES to GENERIC_ARCH_TOPOLOGY

[Helge Deller]

Switch away from the own cpu topology code to common code which is used
by ARM64 and RISCV. That allows us to enable hotplug later on too.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/Kconfig                |  2 +-
 arch/parisc/include/asm/topology.h | 20 +--------
 arch/parisc/kernel/processor.c     |  2 +
 arch/parisc/kernel/topology.c      | 72 +++++++-----------------------
 4 files changed, 19 insertions(+), 77 deletions(-)

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 00cb889bd9a6..6bd42c82a019 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -37,7 +37,7 @@ config PARISC
 	select GENERIC_PCI_IOMAP
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_SMP_IDLE_THREAD
-	select GENERIC_CPU_DEVICES
+	select GENERIC_ARCH_TOPOLOGY
 	select GENERIC_LIB_DEVMEM_IS_ALLOWED
 	select SYSCTL_ARCH_UNALIGN_ALLOW
 	select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/parisc/include/asm/topology.h b/arch/parisc/include/asm/topology.h
index 6f0750c74e47..734eddf096f7 100644
--- a/arch/parisc/include/asm/topology.h
+++ b/arch/parisc/include/asm/topology.h
@@ -4,25 +4,7 @@
 #ifdef CONFIG_PARISC_CPU_TOPOLOGY

 #include <linux/cpumask.h>
-
-struct cputopo_parisc {
-	int thread_id;
-	int core_id;
-	int socket_id;
-	cpumask_t thread_sibling;
-	cpumask_t core_sibling;
-};
-
-extern struct cputopo_parisc cpu_topology[NR_CPUS];
-
-#define topology_physical_package_id(cpu)	(cpu_topology[cpu].socket_id)
-#define topology_core_id(cpu)		(cpu_topology[cpu].core_id)
-#define topology_core_cpumask(cpu)	(&cpu_topology[cpu].core_sibling)
-#define topology_sibling_cpumask(cpu)	(&cpu_topology[cpu].thread_sibling)
-
-void init_cpu_topology(void);
-void store_cpu_topology(unsigned int cpuid);
-const struct cpumask *cpu_coregroup_mask(int cpu);
+#include <linux/arch_topology.h>

 #else

diff --git a/arch/parisc/kernel/processor.c b/arch/parisc/kernel/processor.c
index ccaf075d0750..d0bfd61a4623 100644
--- a/arch/parisc/kernel/processor.c
+++ b/arch/parisc/kernel/processor.c
@@ -19,6 +19,7 @@
 #include <linux/random.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
+#include <asm/topology.h>
 #include <asm/param.h>
 #include <asm/cache.h>
 #include <asm/hardware.h>	/* for register_parisc_driver() stuff */
@@ -459,5 +460,6 @@ static struct parisc_driver cpu_driver __refdata = {
  */
 void __init processor_init(void)
 {
+	reset_cpu_topology();
 	register_parisc_driver(&cpu_driver);
 }
diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c
index e88a6ce7c96d..72d9aeb54fbe 100644
--- a/arch/parisc/kernel/topology.c
+++ b/arch/parisc/kernel/topology.c
@@ -13,45 +13,11 @@
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/sched/topology.h>
+#include <linux/cpu.h>

 #include <asm/topology.h>

- /*
-  * cpu topology table
-  */
-struct cputopo_parisc cpu_topology[NR_CPUS] __read_mostly;
-EXPORT_SYMBOL_GPL(cpu_topology);
-
-const struct cpumask *cpu_coregroup_mask(int cpu)
-{
-	return &cpu_topology[cpu].core_sibling;
-}
-
-static void update_siblings_masks(unsigned int cpuid)
-{
-	struct cputopo_parisc *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
-	int cpu;
-
-	/* update core and thread sibling masks */
-	for_each_possible_cpu(cpu) {
-		cpu_topo = &cpu_topology[cpu];
-
-		if (cpuid_topo->socket_id != cpu_topo->socket_id)
-			continue;
-
-		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
-		if (cpu != cpuid)
-			cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
-
-		if (cpuid_topo->core_id != cpu_topo->core_id)
-			continue;
-
-		cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
-		if (cpu != cpuid)
-			cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
-	}
-	smp_wmb();
-}
+static DEFINE_PER_CPU(struct cpu, cpu_devices);

 static int dualcores_found __initdata;

@@ -62,7 +28,7 @@ static int dualcores_found __initdata;
  */
 void __init store_cpu_topology(unsigned int cpuid)
 {
-	struct cputopo_parisc *cpuid_topo = &cpu_topology[cpuid];
+	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
 	struct cpuinfo_parisc *p;
 	int max_socket = -1;
 	unsigned long cpu;
@@ -71,6 +37,12 @@ void __init store_cpu_topology(unsigned int cpuid)
 	if (cpuid_topo->core_id != -1)
 		return;

+#ifdef CONFIG_HOTPLUG_CPU
+	per_cpu(cpu_devices, cpuid).hotpluggable = 1;
+#endif
+	if (register_cpu(&per_cpu(cpu_devices, cpuid), cpuid))
+		printk("Failed to register CPU device");
+
 	/* create cpu topology mapping */
 	cpuid_topo->thread_id = -1;
 	cpuid_topo->core_id = 0;
@@ -86,25 +58,25 @@ void __init store_cpu_topology(unsigned int cpuid)
 			cpuid_topo->core_id = cpu_topology[cpu].core_id;
 			if (p->cpu_loc) {
 				cpuid_topo->core_id++;
-				cpuid_topo->socket_id = cpu_topology[cpu].socket_id;
+				cpuid_topo->package_id = cpu_topology[cpu].package_id;
 				dualcores_found = 1;
 				continue;
 			}
 		}

-		if (cpuid_topo->socket_id == -1)
-			max_socket = max(max_socket, cpu_topology[cpu].socket_id);
+		if (cpuid_topo->package_id == -1)
+			max_socket = max(max_socket, cpu_topology[cpu].package_id);
 	}

-	if (cpuid_topo->socket_id == -1)
-		cpuid_topo->socket_id = max_socket + 1;
+	if (cpuid_topo->package_id == -1)
+		cpuid_topo->package_id = max_socket + 1;

 	update_siblings_masks(cpuid);

 	pr_info("CPU%u: cpu core %d of socket %d\n",
 		cpuid,
 		cpu_topology[cpuid].core_id,
-		cpu_topology[cpuid].socket_id);
+		cpu_topology[cpuid].package_id);
 }

 static struct sched_domain_topology_level parisc_mc_topology[] = {
@@ -122,20 +94,6 @@ static struct sched_domain_topology_level parisc_mc_topology[] = {
  */
 void __init init_cpu_topology(void)
 {
-	unsigned int cpu;
-
-	/* init core mask and capacity */
-	for_each_possible_cpu(cpu) {
-		struct cputopo_parisc *cpu_topo = &(cpu_topology[cpu]);
-
-		cpu_topo->thread_id = -1;
-		cpu_topo->core_id =  -1;
-		cpu_topo->socket_id = -1;
-		cpumask_clear(&cpu_topo->core_sibling);
-		cpumask_clear(&cpu_topo->thread_sibling);
-	}
-	smp_wmb();
-
 	/* Set scheduler topology descriptor */
 	if (dualcores_found)
 		set_sched_topology(parisc_mc_topology);
--
2.35.1

[PATCH 02/12] parisc: Add __cpuinit section for HOTPLUG_CPU

[Helge Deller]

Provide a __cpuinit section which needs to be used instead of __init
when CPU hotplugging is enabled.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/include/asm/sections.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..4c28c7adaf5f 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -7,6 +7,12 @@

 extern char __alt_instructions[], __alt_instructions_end[];

+#ifdef CONFIG_HOTPLUG_CPU
+#define __cpuinit
+#else
+#define __cpuinit	__init
+#endif
+
 #ifdef CONFIG_64BIT

 #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
--
2.35.1

[PATCH 03/12] parisc: Move store_cpu_topology() into __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/topology.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c
index 72d9aeb54fbe..dc766fb55491 100644
--- a/arch/parisc/kernel/topology.c
+++ b/arch/parisc/kernel/topology.c
@@ -16,17 +16,18 @@
 #include <linux/cpu.h>

 #include <asm/topology.h>
+#include <asm/sections.h>

 static DEFINE_PER_CPU(struct cpu, cpu_devices);

-static int dualcores_found __initdata;
+static int dualcores_found;

 /*
  * store_cpu_topology is called at boot when only one cpu is running
  * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
  * which prevents simultaneous write access to cpu_topology array
  */
-void __init store_cpu_topology(unsigned int cpuid)
+void __cpuinit store_cpu_topology(unsigned int cpuid)
 {
 	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
 	struct cpuinfo_parisc *p;
--
2.35.1

[PATCH 04/12] parisc: Move start_cpu_itimer() into __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index 061119a56fbe..4101392bf74d 100644
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -150,7 +150,7 @@ static struct clocksource clocksource_cr16 = {
 	.flags			= CLOCK_SOURCE_IS_CONTINUOUS,
 };

-void __init start_cpu_itimer(void)
+void __cpuinit start_cpu_itimer(void)
 {
 	unsigned int cpu = smp_processor_id();
 	unsigned long next_tick = mfctl(16) + clocktick;
--
2.35.1

[PATCH 05/12] parisc: Move init_per_cpu() init __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/processor.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/processor.c b/arch/parisc/kernel/processor.c
index d0bfd61a4623..89284e79c159 100644
--- a/arch/parisc/kernel/processor.c
+++ b/arch/parisc/kernel/processor.c
@@ -29,6 +29,7 @@
 #include <asm/pdcpat.h>
 #include <asm/irq.h>		/* for struct irq_region */
 #include <asm/parisc-device.h>
+#include <asm/sections.h>

 struct system_cpuinfo_parisc boot_cpu_data __ro_after_init;
 EXPORT_SYMBOL(boot_cpu_data);
@@ -317,7 +318,7 @@ void __init collect_boot_cpu_data(void)
  *
  * o Enable CPU profiling hooks.
  */
-int __init init_per_cpu(int cpunum)
+int __cpuinit init_per_cpu(int cpunum)
 {
 	int ret;
 	struct pdc_coproc_cfg coproc_cfg;
--
2.35.1

[PATCH 06/12] parisc: Move disable_sr_hashing_asm() into __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/pacache.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S
index b2ba6d633065..661b1834ac94 100644
--- a/arch/parisc/kernel/pacache.S
+++ b/arch/parisc/kernel/pacache.S
@@ -1264,7 +1264,11 @@ ENTRY_CFI(flush_kernel_icache_range_asm)
 	nop
 ENDPROC_CFI(flush_kernel_icache_range_asm)

+#ifdef CONFIG_HOTPLUG_CPU
+	.text
+#else
 	__INIT
+#endif

 	/* align should cover use of rfi in disable_sr_hashing_asm and
 	 * srdis_done.
--
2.35.1

[PATCH 07/12] parisc: Move disable_sr_hashing() into __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 456e879d34a8..6be03d3a2382 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -273,7 +273,7 @@ parisc_cache_init(void)
 	}
 }

-void __init disable_sr_hashing(void)
+void __cpuinit disable_sr_hashing(void)
 {
 	int srhash_type, retval;
 	unsigned long space_bits;
--
2.35.1

[PATCH 08/12] parisc: Move init_IRQ() into __cpuinit section

[Helge Deller]

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c
index eb18e16362f6..a8372db32492 100644
--- a/arch/parisc/kernel/irq.c
+++ b/arch/parisc/kernel/irq.c
@@ -582,7 +582,7 @@ static void claim_cpu_irqs(void)
 #endif
 }

-void __init init_IRQ(void)
+void __cpuinit init_IRQ(void)
 {
 	local_irq_disable();	/* PARANOID - should already be disabled */
 	mtctl(~0UL, 23);	/* EIRR : clear all pending external intr */
--
2.35.1

[PATCH 09/12] parisc: Ensure set_firmware_width() is called only once

[Helge Deller]

Make sure, that set_firmware_width() is only called once at
runtime. This prevents that if secondary CPUs are started later
get stuck in spinlocks.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/firmware.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/firmware.c b/arch/parisc/kernel/firmware.c
index 3370e347dde3..c6b11bdb8602 100644
--- a/arch/parisc/kernel/firmware.c
+++ b/arch/parisc/kernel/firmware.c
@@ -83,7 +83,7 @@ extern unsigned long pdc_result2[NUM_PDC_RESULT];

 /* Firmware needs to be initially set to narrow to determine the
  * actual firmware width. */
-int parisc_narrow_firmware __ro_after_init = 1;
+int parisc_narrow_firmware __ro_after_init = 2;
 #endif

 /* On most currently-supported platforms, IODC I/O calls are 32-bit calls
@@ -174,6 +174,11 @@ void set_firmware_width_unlocked(void)
 void set_firmware_width(void)
 {
 	unsigned long flags;
+
+	/* already initialized? */
+	if (parisc_narrow_firmware != 2)
+		return;
+
 	spin_lock_irqsave(&pdc_lock, flags);
 	set_firmware_width_unlocked();
 	spin_unlock_irqrestore(&pdc_lock, flags);
--
2.35.1

[PATCH 10/12] parisc: Move common_stext into text section when CONFIG_HOTPLUG_CPU=y

[Helge Deller]

Move the common_stext function into the non-init text section if hotplug
is enabled. This function is called from the firmware when secondary
CPUS are brought up when CPU hotplug is enabled.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/head.S | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/kernel/head.S b/arch/parisc/kernel/head.S
index b24f77748c22..e0a9e9657622 100644
--- a/arch/parisc/kernel/head.S
+++ b/arch/parisc/kernel/head.S
@@ -162,6 +162,15 @@ $pgt_fill_loop:
 	/* FALLTHROUGH */
 	.procend

+#ifdef CONFIG_HOTPLUG_CPU
+	/* common_stext is far away in another section... jump there */
+	load32		PA(common_stext), %rp
+	bv,n		(%rp)
+
+	/* common_stext and smp_slave_stext needs to be in text section */
+	.text
+#endif
+
 	/*
 	** Code Common to both Monarch and Slave processors.
 	** Entry:
@@ -371,8 +380,6 @@ smp_slave_stext:
 	.procend
 #endif /* CONFIG_SMP */

-ENDPROC(parisc_kernel_start)
-
 #ifndef CONFIG_64BIT
 	.section .data..ro_after_init

--
2.35.1

[PATCH 11/12] parisc: Rewrite arch_cpu_idle_dead() for CPU hotplugging

[Helge Deller]

Let the PDC firmware put the CPU into firmware idle loop with
pdc_cpu_rendezvous() function.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/process.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index ea3d83b6fb62..44fa89fbb280 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -38,6 +38,7 @@
 #include <linux/rcupdate.h>
 #include <linux/random.h>
 #include <linux/nmi.h>
+#include <linux/sched/hotplug.h>

 #include <asm/io.h>
 #include <asm/asm-offsets.h>
@@ -46,6 +47,7 @@
 #include <asm/pdc_chassis.h>
 #include <asm/unwind.h>
 #include <asm/sections.h>
+#include <asm/cacheflush.h>

 #define COMMAND_GLOBAL  F_EXTEND(0xfffe0030)
 #define CMD_RESET       5       /* reset any module */
@@ -158,10 +160,35 @@ void release_thread(struct task_struct *dead_task)
 int running_on_qemu __ro_after_init;
 EXPORT_SYMBOL(running_on_qemu);

-void __cpuidle arch_cpu_idle_dead(void)
+/*
+ * Called from the idle thread for the CPU which has been shutdown.
+ */
+void arch_cpu_idle_dead(void)
 {
-	/* nop on real hardware, qemu will offline CPU. */
-	asm volatile("or %%r31,%%r31,%%r31\n":::);
+#ifdef CONFIG_HOTPLUG_CPU
+	idle_task_exit();
+
+	local_irq_disable();
+
+	/*
+	 * Tell __cpu_die() that this CPU is now safe to dispose of.
+	 */
+	(void)cpu_report_death();
+
+	/*
+	 * Ensure that the cache lines are written out.
+	 */
+	flush_cache_all_local();
+	flush_tlb_all_local(NULL);
+
+	/*
+	 * Let PDC firmware put CPU into firmware idle loop.
+	 */
+	__pdc_cpu_rendezvous();
+
+	pr_warn("PDC does not provide rendezvous function.\n");
+#endif
+	while (1);
 }

 void __cpuidle arch_cpu_idle(void)
--
2.35.1

[PATCH 12/12] parisc: Implement __cpu_die() and __cpu_disable() for CPU hotplugging

[Helge Deller]

Add relevant code to __cpu_die() and __cpu_disable() to finally enable
the CPU hotplugging features. Reset the irq count values in smp_callin()
to zero before bringing up the CPU.

Use "chcpu -d 1" to bring CPU1 down, and "chcpu -e 1" to bring it up.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/Kconfig           |  1 +
 arch/parisc/include/asm/smp.h |  9 +---
 arch/parisc/kernel/smp.c      | 80 +++++++++++++++++++++++++++++++++--
 3 files changed, 79 insertions(+), 11 deletions(-)

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 6bd42c82a019..ec5bb9626d06 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -56,6 +56,7 @@ config PARISC
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select GENERIC_SCHED_CLOCK
+	select GENERIC_IRQ_MIGRATION
 	select HAVE_UNSTABLE_SCHED_CLOCK if SMP
 	select LEGACY_TIMER_TICK
 	select CPU_NO_EFFICIENT_FFS
diff --git a/arch/parisc/include/asm/smp.h b/arch/parisc/include/asm/smp.h
index 2279ebe5e2da..94d1f21ce99a 100644
--- a/arch/parisc/include/asm/smp.h
+++ b/arch/parisc/include/asm/smp.h
@@ -44,12 +44,7 @@ static inline void smp_send_all_nop(void) { return; }

 #define NO_PROC_ID		0xFF		/* No processor magic marker */
 #define ANY_PROC_ID		0xFF		/* Any processor magic marker */
-static inline int __cpu_disable (void) {
-  return 0;
-}
-static inline void __cpu_die (unsigned int cpu) {
-  while(1)
-    ;
-}
+int __cpu_disable(void);
+void __cpu_die(unsigned int cpu);

 #endif /*  __ASM_SMP_H */
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index a32a882a2d58..60cc33fd345c 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -30,6 +30,7 @@
 #include <linux/ftrace.h>
 #include <linux/cpu.h>
 #include <linux/kgdb.h>
+#include <linux/sched/hotplug.h>

 #include <linux/atomic.h>
 #include <asm/current.h>
@@ -309,7 +310,7 @@ smp_cpu_init(int cpunum)
  * Slaves start using C here. Indirectly called from smp_slave_stext.
  * Do what start_kernel() and main() do for boot strap processor (aka monarch)
  */
-void __init smp_callin(unsigned long pdce_proc)
+void __cpuinit smp_callin(unsigned long pdce_proc)
 {
 	int slave_id = cpu_now_booting;

@@ -339,6 +340,19 @@ int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
 	const struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpuid);
 	long timeout;

+#ifdef CONFIG_HOTPLUG_CPU
+	int i;
+
+	/* reset irq statistics for this CPU */
+	memset(&per_cpu(irq_stat, cpuid), 0, sizeof(irq_cpustat_t));
+	for (i = 0; i < NR_IRQS; i++) {
+		struct irq_desc *desc = irq_to_desc(i);
+
+		if (desc && desc->kstat_irqs)
+			*per_cpu_ptr(desc->kstat_irqs, cpuid) = 0;
+	}
+#endif
+
 	/* Let _start know what logical CPU we're booting
 	** (offset into init_tasks[],cpu_data[])
 	*/
@@ -430,10 +444,68 @@ void smp_cpus_done(unsigned int cpu_max)

 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
-	if (cpu != 0 && cpu < parisc_max_cpus && smp_boot_one_cpu(cpu, tidle))
-		return -ENOSYS;
+	if (cpu_online(cpu))
+		return 0;
+
+	if (num_online_cpus() < parisc_max_cpus && smp_boot_one_cpu(cpu, tidle))
+		return -EIO;
+
+	return cpu_online(cpu) ? 0 : -EIO;
+}
+
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpu_disable(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	unsigned int cpu = smp_processor_id();
+
+	remove_cpu_topology(cpu);
+
+	/*
+	 * Take this CPU offline.  Once we clear this, we can't return,
+	 * and we must not schedule until we're ready to give up the cpu.
+	 */
+	set_cpu_online(cpu, false);
+
+	/*
+	 * disable IPI interrupt
+	 */
+	disable_percpu_irq(IPI_IRQ);
+
+	/*
+	 * migrate IRQs away from this CPU
+	 */
+	irq_migrate_all_off_this_cpu();
+
+	/*
+	 * Flush user cache and TLB mappings, and then remove this CPU
+	 * from the vm mask set of all processes.
+	 *
+	 * Caches are flushed to the Level of Unification Inner Shareable
+	 * to write-back dirty lines to unified caches shared by all CPUs.
+	 */
+	flush_cache_all_local();
+	flush_tlb_all_local(NULL);

-	return cpu_online(cpu) ? 0 : -ENOSYS;
+	/* disable all irqs, including timer irq */
+	local_irq_disable();
+#endif
+	return 0;
+}
+
+/*
+ * called on the thread which is asking for a CPU to be shutdown -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpu_die(unsigned int cpu)
+{
+	if (!cpu_wait_death(cpu, 5)) {
+		pr_crit("CPU%u: cpu didn't die\n", cpu);
+		return;
+	}
+	pr_debug("CPU%u: shutdown\n", cpu);
 }

 #ifdef CONFIG_PROC_FS
--
2.35.1

Re: [PATCH 01/12] parisc: Switch from GENERIC_CPU_DEVICES to GENERIC_ARCH_TOPOLOGY

[Helge Deller]

On 3/25/22 15:38, Helge Deller wrote:
> Switch away from the own cpu topology code to common code which is used
> by ARM64 and RISCV. That allows us to enable hotplug later on too.

With this series I was able to use CPU hotplugging on the PA-RISC machines.
I sucessfully tested it on qemu (32bit kernel) and on a 2-way C8000 (64bit kernel).

For qemu the patch I committed today is required:
https://github.com/hdeller/seabios-hppa/commit/5cec13f11d3917cf3bceaf68ce23e9fa5f206a35

There is still some issue with the irq balancing on qemu with the emulated GSC, e.g. in this
example with 3 CPUs you can only disable CPU0 or CPU2, which both don't use any IRQs.
During shutdown of CPU1 the irqs 17-20 needs to be moved to another CPU which doesn't
work reliable yet.

Example:

root@debian:~# cat /proc/interrupts
           CPU0       CPU1       CPU2
 17:          0          0          0        GSC-ASIC  parport0
 18:          0       1759          0         GSC-PCI  ttyS0
 19:          0       3572          0         GSC-PCI  sym53c8xx
 20:          0       2359          0         GSC-PCI  enp0s1
 64:        224     148358     128518             CPU  timer
 65:         16       4224        677             CPU  IPI
 66:          0          0          0             CPU  lasi
 67:          0       8758          0             CPU  Dino
STK:       2240       6080       3072   Kernel stack usage

root@debian:~# chcpu -d 2	# disables CPU2
CPU 2 disabled

root@debian:~# cat /proc/interrupts
           CPU0       CPU1
 17:          0          0        GSC-ASIC  parport0
 18:          0       1843         GSC-PCI  ttyS0
 19:          0       3662         GSC-PCI  sym53c8xx
 20:...

root@debian:~# chcpu -e 2	# enable CPU2
[    6.466714] Releasing cpu 2 now, hpa=fffb2000
CPU 2 enabled

root@debian:~# cat /proc/interrupts
           CPU0       CPU1       CPU2
 17:          0          0          0        GSC-ASIC  parport0
 18:          0       1915          0         GSC-PCI  ttyS0
 19:          0       3668          0         GSC-PCI  sym53c8xx
...

CPU hotplugging on the C8000 seems to work reliable.

Helge

Re: [PATCH 01/12] parisc: Switch from GENERIC_CPU_DEVICES to GENERIC_ARCH_TOPOLOGY

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:22 CET schrieb Helge Deller:
> Switch away from the own cpu topology code to common code which is used
> by ARM64 and RISCV. That allows us to enable hotplug later on too.

> diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c
> index e88a6ce7c96d..72d9aeb54fbe 100644
> --- a/arch/parisc/kernel/topology.c
> +++ b/arch/parisc/kernel/topology.c
> @@ -71,6 +37,12 @@ void __init store_cpu_topology(unsigned int cpuid)
>  	if (cpuid_topo->core_id != -1)
>  		return;
> 
> +#ifdef CONFIG_HOTPLUG_CPU
> +	per_cpu(cpu_devices, cpuid).hotpluggable = 1;
> +#endif
> +	if (register_cpu(&per_cpu(cpu_devices, cpuid), cpuid))
> +		printk("Failed to register CPU device");
> +

This seems to be missing a level, and I think also printing the id of the 
failing CPU wouldn't hurt either.


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Re: [PATCH 03/12] parisc: Move store_cpu_topology() into __cpuinit section

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:24 CET schrieb Helge Deller:
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
>  arch/parisc/kernel/topology.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c
> index 72d9aeb54fbe..dc766fb55491 100644
> --- a/arch/parisc/kernel/topology.c
> +++ b/arch/parisc/kernel/topology.c
> @@ -16,17 +16,18 @@
>  #include <linux/cpu.h>
> 
>  #include <asm/topology.h>
> +#include <asm/sections.h>
> 
>  static DEFINE_PER_CPU(struct cpu, cpu_devices);
> 
> -static int dualcores_found __initdata;
> +static int dualcores_found;

I wonder if that should not be something like __cpuinit_data.

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Re: [PATCH 04/12] parisc: Move start_cpu_itimer() into __cpuinit section

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:25 CET schrieb Helge Deller:
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
>  arch/parisc/kernel/time.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
> index 061119a56fbe..4101392bf74d 100644
> --- a/arch/parisc/kernel/time.c
> +++ b/arch/parisc/kernel/time.c
> @@ -150,7 +150,7 @@ static struct clocksource clocksource_cr16 = {
>  	.flags			= CLOCK_SOURCE_IS_CONTINUOUS,
>  };
> 
> -void __init start_cpu_itimer(void)
> +void __cpuinit start_cpu_itimer(void)
>  {
>  	unsigned int cpu = smp_processor_id();
>  	unsigned long next_tick = mfctl(16) + clocktick;

I would have squashed this and 5, 7, and 8 together. None of these patches 
adds any sensible description and all do the same.

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Re: [PATCH 11/12] parisc: Rewrite arch_cpu_idle_dead() for CPU hotplugging

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:32 CET schrieb Helge Deller:
> Let the PDC firmware put the CPU into firmware idle loop with
> pdc_cpu_rendezvous() function.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
>  arch/parisc/kernel/process.c | 33 ++++++++++++++++++++++++++++++---
>  1 file changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index ea3d83b6fb62..44fa89fbb280 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -38,6 +38,7 @@
>  #include <linux/rcupdate.h>
>  #include <linux/random.h>
>  #include <linux/nmi.h>
> +#include <linux/sched/hotplug.h>
> 
>  #include <asm/io.h>
>  #include <asm/asm-offsets.h>
> @@ -46,6 +47,7 @@
>  #include <asm/pdc_chassis.h>
>  #include <asm/unwind.h>
>  #include <asm/sections.h>
> +#include <asm/cacheflush.h>
> 
>  #define COMMAND_GLOBAL  F_EXTEND(0xfffe0030)
>  #define CMD_RESET       5       /* reset any module */
> @@ -158,10 +160,35 @@ void release_thread(struct task_struct *dead_task)
>  int running_on_qemu __ro_after_init;
>  EXPORT_SYMBOL(running_on_qemu);
> 
> -void __cpuidle arch_cpu_idle_dead(void)
> +/*
> + * Called from the idle thread for the CPU which has been shutdown.
> + */
> +void arch_cpu_idle_dead(void)
>  {
> -	/* nop on real hardware, qemu will offline CPU. */
> -	asm volatile("or %%r31,%%r31,%%r31\n":::);
> +#ifdef CONFIG_HOTPLUG_CPU
> +	idle_task_exit();
> +
> +	local_irq_disable();
> +
> +	/*
> +	 * Tell __cpu_die() that this CPU is now safe to dispose of.
> +	 */
> +	(void)cpu_report_death();
> +
> +	/*
> +	 * Ensure that the cache lines are written out.
> +	 */
> +	flush_cache_all_local();
> +	flush_tlb_all_local(NULL);
> +
> +	/*
> +	 * Let PDC firmware put CPU into firmware idle loop.
> +	 */
> +	__pdc_cpu_rendezvous();

That could all be one-line comments for a higher code/line ratio ;)

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Re: [PATCH 12/12] parisc: Implement __cpu_die() and __cpu_disable() for CPU hotplugging

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:33 CET schrieb Helge Deller:
> Add relevant code to __cpu_die() and __cpu_disable() to finally enable
> the CPU hotplugging features. Reset the irq count values in smp_callin()
> to zero before bringing up the CPU.
> 
> Use "chcpu -d 1" to bring CPU1 down, and "chcpu -e 1" to bring it up.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
>  arch/parisc/Kconfig           |  1 +
>  arch/parisc/include/asm/smp.h |  9 +---
>  arch/parisc/kernel/smp.c      | 80 +++++++++++++++++++++++++++++++++--
>  3 files changed, 79 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
> index a32a882a2d58..60cc33fd345c 100644
> --- a/arch/parisc/kernel/smp.c
> +++ b/arch/parisc/kernel/smp.c
> @@ -430,10 +444,68 @@ void smp_cpus_done(unsigned int cpu_max)
> 
>  int __cpu_up(unsigned int cpu, struct task_struct *tidle)
>  {
> -	if (cpu != 0 && cpu < parisc_max_cpus && smp_boot_one_cpu(cpu, 
tidle))
> -		return -ENOSYS;
> +	if (cpu_online(cpu))
> +		return 0;
> +
> +	if (num_online_cpus() < parisc_max_cpus && smp_boot_one_cpu(cpu, 
tidle))
> +		return -EIO;

I had to look up parisc_max_cpus, and found this:

> static int parisc_max_cpus = 1;

Hm, signed?

> parisc_max_cpus = max_cpus;
>        if (!max_cpus)
>                printk(KERN_INFO "SMP mode deactivated.\n");

So parisc_max_cpus is now 0, which seems wrong. Shouldn't the check be before 
the assignment? This would have avoided the "cpu != 0" in the old code 
completely.

> +
> +	return cpu_online(cpu) ? 0 : -EIO;
> +}
> +
> +/*
> + * __cpu_disable runs on the processor to be shutdown.
> + */
> +int __cpu_disable(void)
> +{
> +#ifdef CONFIG_HOTPLUG_CPU
> +	unsigned int cpu = smp_processor_id();
> +
> +	remove_cpu_topology(cpu);
> +
> +	/*
> +	 * Take this CPU offline.  Once we clear this, we can't return,
> +	 * and we must not schedule until we're ready to give up the cpu.
> +	 */
> +	set_cpu_online(cpu, false);
> +
> +	/*
> +	 * disable IPI interrupt
> +	 */
> +	disable_percpu_irq(IPI_IRQ);
> +
> +	/*
> +	 * migrate IRQs away from this CPU
> +	 */
> +	irq_migrate_all_off_this_cpu();

While I really enjoy good code comments the last 2 seem a t bit wasteful, 
given that the code is basically exactly the same as the text.

> +	/*
> +	 * Flush user cache and TLB mappings, and then remove this CPU
> +	 * from the vm mask set of all processes.
> +	 *
> +	 * Caches are flushed to the Level of Unification Inner Shareable
> +	 * to write-back dirty lines to unified caches shared by all CPUs.
> +	 */
> +	flush_cache_all_local();
> +	flush_tlb_all_local(NULL);
> 
> -	return cpu_online(cpu) ? 0 : -ENOSYS;
> +	/* disable all irqs, including timer irq */
> +	local_irq_disable();
> +#endif
> +	return 0;
> +}
> +
> +/*
> + * called on the thread which is asking for a CPU to be shutdown -
> + * waits until shutdown has completed, or it is timed out.
> + */
> +void __cpu_die(unsigned int cpu)
> +{
> +	if (!cpu_wait_death(cpu, 5)) {
> +		pr_crit("CPU%u: cpu didn't die\n", cpu);
> +		return;
> +	}
> +	pr_debug("CPU%u: shutdown\n", cpu);
>  }
> 
>  #ifdef CONFIG_PROC_FS
> --
> 2.35.1


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Re: [PATCH 03/12] parisc: Move store_cpu_topology() into __cpuinit section

[Helge Deller]

On 3/25/22 17:52, Rolf Eike Beer wrote:
> Am Freitag, 25. März 2022, 15:38:24 CET schrieb Helge Deller:
>> Signed-off-by: Helge Deller <deller@gmx.de>
>> ---
>>  arch/parisc/kernel/topology.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c
>> index 72d9aeb54fbe..dc766fb55491 100644
>> --- a/arch/parisc/kernel/topology.c
>> +++ b/arch/parisc/kernel/topology.c
>> @@ -16,17 +16,18 @@
>>  #include <linux/cpu.h>
>>
>>  #include <asm/topology.h>
>> +#include <asm/sections.h>
>>
>>  static DEFINE_PER_CPU(struct cpu, cpu_devices);
>>
>> -static int dualcores_found __initdata;
>> +static int dualcores_found;
>
> I wonder if that should not be something like __cpuinit_data.

Heh ... all other platforms got rid of __cpuinit and __cpuinit_data.
I just wanted to keep it on parisc in order to have small code in case of UP.
That said, introducing a __cpuinit_data section for this single variable didn't made sense.

Helge

Re: [PATCH 04/12] parisc: Move start_cpu_itimer() into __cpuinit section

[Helge Deller]

On 3/25/22 17:53, Rolf Eike Beer wrote:
> Am Freitag, 25. März 2022, 15:38:25 CET schrieb Helge Deller:
>> Signed-off-by: Helge Deller <deller@gmx.de>
>> ---
>>  arch/parisc/kernel/time.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
>> index 061119a56fbe..4101392bf74d 100644
>> --- a/arch/parisc/kernel/time.c
>> +++ b/arch/parisc/kernel/time.c
>> @@ -150,7 +150,7 @@ static struct clocksource clocksource_cr16 = {
>>  	.flags			= CLOCK_SOURCE_IS_CONTINUOUS,
>>  };
>>
>> -void __init start_cpu_itimer(void)
>> +void __cpuinit start_cpu_itimer(void)
>>  {
>>  	unsigned int cpu = smp_processor_id();
>>  	unsigned long next_tick = mfctl(16) + clocktick;
>
> I would have squashed this and 5, 7, and 8 together. None of these patches
> adds any sensible description and all do the same.

Yes, maybe I'll do that. Keeping them seperate makes handling easier for me.

Helge

Re: [PATCH 11/12] parisc: Rewrite arch_cpu_idle_dead() for CPU hotplugging

[Helge Deller]

On 3/25/22 17:56, Rolf Eike Beer wrote:
> Am Freitag, 25. März 2022, 15:38:32 CET schrieb Helge Deller:
>> Let the PDC firmware put the CPU into firmware idle loop with
>> pdc_cpu_rendezvous() function.
>>
>> Signed-off-by: Helge Deller <deller@gmx.de>
>> ---
>>  arch/parisc/kernel/process.c | 33 ++++++++++++++++++++++++++++++---
>>  1 file changed, 30 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
>> index ea3d83b6fb62..44fa89fbb280 100644
>> --- a/arch/parisc/kernel/process.c
>> +++ b/arch/parisc/kernel/process.c
>> @@ -38,6 +38,7 @@
>>  #include <linux/rcupdate.h>
>>  #include <linux/random.h>
>>  #include <linux/nmi.h>
>> +#include <linux/sched/hotplug.h>
>>
>>  #include <asm/io.h>
>>  #include <asm/asm-offsets.h>
>> @@ -46,6 +47,7 @@
>>  #include <asm/pdc_chassis.h>
>>  #include <asm/unwind.h>
>>  #include <asm/sections.h>
>> +#include <asm/cacheflush.h>
>>
>>  #define COMMAND_GLOBAL  F_EXTEND(0xfffe0030)
>>  #define CMD_RESET       5       /* reset any module */
>> @@ -158,10 +160,35 @@ void release_thread(struct task_struct *dead_task)
>>  int running_on_qemu __ro_after_init;
>>  EXPORT_SYMBOL(running_on_qemu);
>>
>> -void __cpuidle arch_cpu_idle_dead(void)
>> +/*
>> + * Called from the idle thread for the CPU which has been shutdown.
>> + */
>> +void arch_cpu_idle_dead(void)
>>  {
>> -	/* nop on real hardware, qemu will offline CPU. */
>> -	asm volatile("or %%r31,%%r31,%%r31\n":::);
>> +#ifdef CONFIG_HOTPLUG_CPU
>> +	idle_task_exit();
>> +
>> +	local_irq_disable();
>> +
>> +	/*
>> +	 * Tell __cpu_die() that this CPU is now safe to dispose of.
>> +	 */
>> +	(void)cpu_report_death();
>> +
>> +	/*
>> +	 * Ensure that the cache lines are written out.
>> +	 */
>> +	flush_cache_all_local();
>> +	flush_tlb_all_local(NULL);
>> +
>> +	/*
>> +	 * Let PDC firmware put CPU into firmware idle loop.
>> +	 */
>> +	__pdc_cpu_rendezvous();
>
> That could all be one-line comments for a higher code/line ratio ;)

Yes. The syntax is mostly copied from other arches, where it's like this.

Helge

Re: [PATCH 12/12] parisc: Implement __cpu_die() and __cpu_disable() for CPU hotplugging

[Helge Deller]

On 3/25/22 18:10, Rolf Eike Beer wrote:
> Am Freitag, 25. März 2022, 15:38:33 CET schrieb Helge Deller:
>> Add relevant code to __cpu_die() and __cpu_disable() to finally enable
>> the CPU hotplugging features. Reset the irq count values in smp_callin()
>> to zero before bringing up the CPU.
>>
>> Use "chcpu -d 1" to bring CPU1 down, and "chcpu -e 1" to bring it up.
>>
>> Signed-off-by: Helge Deller <deller@gmx.de>
>> ---
>>  arch/parisc/Kconfig           |  1 +
>>  arch/parisc/include/asm/smp.h |  9 +---
>>  arch/parisc/kernel/smp.c      | 80 +++++++++++++++++++++++++++++++++--
>>  3 files changed, 79 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
>> index a32a882a2d58..60cc33fd345c 100644
>> --- a/arch/parisc/kernel/smp.c
>> +++ b/arch/parisc/kernel/smp.c
>> @@ -430,10 +444,68 @@ void smp_cpus_done(unsigned int cpu_max)
>>
>>  int __cpu_up(unsigned int cpu, struct task_struct *tidle)
>>  {
>> -	if (cpu != 0 && cpu < parisc_max_cpus && smp_boot_one_cpu(cpu,
> tidle))
>> -		return -ENOSYS;
>> +	if (cpu_online(cpu))
>> +		return 0;
>> +
>> +	if (num_online_cpus() < parisc_max_cpus && smp_boot_one_cpu(cpu,
> tidle))
>> +		return -EIO;
>
> I had to look up parisc_max_cpus, and found this:
>
>> static int parisc_max_cpus = 1;
>
> Hm, signed?
>
>> parisc_max_cpus = max_cpus;
>>        if (!max_cpus)
>>                printk(KERN_INFO "SMP mode deactivated.\n");
>
> So parisc_max_cpus is now 0, which seems wrong. Shouldn't the check be before
> the assignment? This would have avoided the "cpu != 0" in the old code
> completely.

No, the old
	cpu != 0 && ....smp_boot_one_cpu(cpu, tidle))
was to avoid that smp_boot_one_cpu() gets called for the monarch cpu.

Anyway, you are right, the code could need cleanups.
But in my patch series I wanted to keep the changes minimal in the first place.

>
>> +
>> +	return cpu_online(cpu) ? 0 : -EIO;
>> +}
>> +
>> +/*
>> + * __cpu_disable runs on the processor to be shutdown.
>> + */
>> +int __cpu_disable(void)
>> +{
>> +#ifdef CONFIG_HOTPLUG_CPU
>> +	unsigned int cpu = smp_processor_id();
>> +
>> +	remove_cpu_topology(cpu);
>> +
>> +	/*
>> +	 * Take this CPU offline.  Once we clear this, we can't return,
>> +	 * and we must not schedule until we're ready to give up the cpu.
>> +	 */
>> +	set_cpu_online(cpu, false);
>> +
>> +	/*
>> +	 * disable IPI interrupt
>> +	 */
>> +	disable_percpu_irq(IPI_IRQ);
>> +
>> +	/*
>> +	 * migrate IRQs away from this CPU
>> +	 */
>> +	irq_migrate_all_off_this_cpu();
>
> While I really enjoy good code comments the last 2 seem a t bit wasteful,
> given that the code is basically exactly the same as the text.

Yep.

Helge

Re: [PATCH 09/12] parisc: Ensure set_firmware_width() is called only once

[Rolf Eike Beer]

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Am Freitag, 25. März 2022, 15:38:30 CET schrieb Helge Deller:
> Make sure, that set_firmware_width() is only called once at
> runtime. This prevents that if secondary CPUs are started later
> get stuck in spinlocks.

The second sentence seems to be missing a word.

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