ARM: tegra30: fix power up sequence for boot_secondary

PATCH New Joseph Lo 3 participants 5 messages Dec 20, 2012 – Jan 2, 2013

Subsystems (3)

Arm (32-bit) Arm sub-architectures Tegra architecture support

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Joseph Lo

author

2012-12-20 02:30 UTC #0 lore raw

PATCH 1/1 ARM: tegra30: fix power up sequence for boot_secondary

The power up sequence is different on the cold boot CPU and the CPU that resumed from the hotplug. For the cold boot CPU, it was been power gated as default. To power up the cold boot CPU, the power should be un-gated by un toggling the power gate register manually.

For the CPU that resumed from the hotplug, after un-halted the CPU. The flow controller will un-gate the power of the CPU. No need to manually control, just wait the power be resumed and continue the power up sequence after the CPU power is ready.

Based on the work by:
Varun Wadekar <[email protected]>

Signed-off-by Joseph Lo <[email protected]>

---
 arch/arm/mach-tegra/platsmp.c |   31 ++++++++++++++++++++++++++++++-
 1 files changed, 30 insertions(+), 1 deletions(-)

arch/arm/mach-tegra/platsmp.c +30 -1

index 6cedb3e..9bd4898 100644
@@ -23,6 +23,7 @@
 #include <asm/hardware/gic.h>
 #include <asm/mach-types.h>
 #include <asm/smp_scu.h>
+#include <asm/smp_plat.h>
 
 #include <mach/powergate.h>

@@ -36,6 +37,7 @@
 
 extern void tegra_secondary_startup(void);
 
+static cpumask_t tegra_cpu_init_mask;
 static void __iomem *scu_base = IO_ADDRESS(TEGRA_ARM_PERIF_BASE);
 
 #define EVP_CPU_RESET_VECTOR \

@@ -50,6 +52,7 @@ static void __cpuinit tegra_secondary_init(unsigned int cpu)
 	 */
 	gic_secondary_init(0);
 
+	cpumask_set_cpu(cpu, &tegra_cpu_init_mask);
 }
 
 static int tegra20_power_up_cpu(unsigned int cpu)

@@ -72,7 +75,27 @@ static int tegra30_power_up_cpu(unsigned int cpu)
 	if (pwrgateid < 0)
 		return pwrgateid;
 
-	/* If this is the first boot, toggle powergates directly. */
+	/*
+	 * If the CPU had booted and went through here after CPU
+	 * had been already un-gated by flow controller. Wait
+	 * for confirmation that the CPU is powered then remove
+	 * the IO clamps. On the cold boot entry, do not wait.
+	 */
+	if (cpumask_test_cpu(cpu, &tegra_cpu_init_mask)) {
+		timeout = jiffies + 5;
+		do {
+			if (!tegra_powergate_is_powered(pwrgateid))
+				goto remove_clamps;
+			udelay(10);
+		} while (time_before(jiffies, timeout));
+	}
+
+	/*
+	 * The power status of the cold boot CPU is power gating as
+	 * default. To power up the cold boot CPU, the power should
+	 * be un-gated by un-toggling the power gate register
+	 * manually.
+	 */
 	if (!tegra_powergate_is_powered(pwrgateid)) {
 		ret = tegra_powergate_power_on(pwrgateid);
 		if (ret)

@@ -87,6 +110,7 @@ static int tegra30_power_up_cpu(unsigned int cpu)
 		}
 	}
 
+remove_clamps:
 	/* CPU partition is powered. Enable the CPU clock. */
 	tegra_enable_cpu_clock(cpu);
 	udelay(10);

@@ -105,6 +129,8 @@ static int __cpuinit tegra_boot_secondary(unsigned int cpu, struct task_struct *
 {
 	int status;
 
+	cpu = cpu_logical_map(cpu);
+
 	/*
 	 * Force the CPU into reset. The CPU must remain in reset when the
 	 * flow controller state is cleared (which will cause the flow

@@ -165,6 +191,9 @@ static void __init tegra_smp_init_cpus(void)
 
 static void __init tegra_smp_prepare_cpus(unsigned int max_cpus)
 {
+	/* Always mark the boot CPU (CPU0) as initialized. */
+	cpumask_set_cpu(0, &tegra_cpu_init_mask);
+
 	tegra_cpu_reset_handler_init();
 	scu_enable(scu_base);
 }

Signature · 1 line

1.7.0.4

Stephen Warren

2012-12-20 16:55 UTC #1 lore raw

PATCH 1/1 ARM: tegra30: fix power up sequence for boot_secondary

Quoted 9 lines · Joseph Lo

The power up sequence is different on the cold boot CPU and the CPU that resumed from the hotplug. For the cold boot CPU, it was been power gated as default. To power up the cold boot CPU, the power should be un-gated by un toggling the power gate register manually.
For the CPU that resumed from the hotplug, after un-halted the CPU. The flow controller will un-gate the power of the CPU. No need to manually control, just wait the power be resumed and continue the power up sequence after the CPU power is ready.

I'd like Peter to review this too (CC'd). I guess it looks OK...

arch/arm/mach-tegra/platsmp.c static int tegra30_power_up_cpu(unsigned int cpu) · line 83

Quoted 13 lines

arch/arm/mach-tegra/platsmp.c +6 -1

@@ -72,7 +75,27 @@ static int tegra30_power_up_cpu(unsigned int cpu)
 	if (pwrgateid < 0)
 		return pwrgateid;
 
-	/* If this is the first boot, toggle powergates directly. */
+	/*
+	 * If the CPU had booted and went through here after CPU
+	 * had been already un-gated by flow controller. Wait
+	 * for confirmation that the CPU is powered then remove
+	 * the IO clamps. On the cold boot entry, do not wait.
+	 */

That comment is quite unclear. In particular the first sentence says "if something" rather than "if something then something". Can you please re-write it?

Also, it'd be good to explain (or at least briefly reference) the boot path for a cold-boot CPU and a warm boot CPU; I assume that somehow a cold boot CPU doesn't execute tegra_secondary_init(), but a warm boot CPU does?

arch/arm/mach-tegra/platsmp.c static int tegra30_power_up_cpu(unsigned int cpu) · line 85

Quoted 2 lines

arch/arm/mach-tegra/platsmp.c +2 -0

+	if (cpumask_test_cpu(cpu, &tegra_cpu_init_mask)) {
+		timeout = jiffies + 5;

Are the units/frequency of the jiffies variable always constant? Should "5" be not a constant, but instead a calculation involving HZ or msecs_to_jiffies()? Certainly, the few other uses of time_before() I looked at use HZ or msecs_to_jiffies().

Joseph Lo

author

2012-12-21 08:07 UTC #2 lore raw

PATCH 1/1 ARM: tegra30: fix power up sequence for boot_secondary

Quoted 19 lines · Stephen Warren

Quoted 9 lines · Joseph Lo
The power up sequence is different on the cold boot CPU and the CPU that resumed from the hotplug. For the cold boot CPU, it was been power gated as default. To power up the cold boot CPU, the power should be un-gated by un toggling the power gate register manually.
For the CPU that resumed from the hotplug, after un-halted the CPU. The flow controller will un-gate the power of the CPU. No need to manually control, just wait the power be resumed and continue the power up sequence after the CPU power is ready.
I'd like Peter to review this too (CC'd). I guess it looks OK...
Quoted 6 lines
arch/arm/mach-tegra/platsmp.c +0 -0
@@ -72,7 +75,27 @@ static int tegra30_power_up_cpu(unsigned int cpu)
 	if (pwrgateid < 0)
 		return pwrgateid;
 

Quoted 12 lines

arch/arm/mach-tegra/platsmp.c static int tegra30_power_up_cpu(unsigned int cpu) · line 83
Quoted 7 lines
arch/arm/mach-tegra/platsmp.c +6 -1
-	/* If this is the first boot, toggle powergates directly. */
+	/*
+	 * If the CPU had booted and went through here after CPU
+	 * had been already un-gated by flow controller. Wait
+	 * for confirmation that the CPU is powered then remove
+	 * the IO clamps. On the cold boot entry, do not wait.
+	 */
That comment is quite unclear. In particular the first sentence says "if something" rather than "if something then something". Can you please re-write it?

OK.

Quoted 5 lines

Also, it'd be good to explain (or at least briefly reference) the boot path for a cold-boot CPU and a warm boot CPU; I assume that somehow a cold boot CPU doesn't execute tegra_secondary_init(), but a warm boot CPU does?

The boot path was the same. Both of the conditions were booted from tegra_boot_secondary. Just the power sequence has been different. We add the code to recover the power up sequence of warm boot CPU.

Thanks,
Joseph

Stephen Warren

2012-12-21 21:12 UTC #3 lore raw

PATCH 1/1 ARM: tegra30: fix power up sequence for boot_secondary

Quoted 11 lines · Joseph Lo

Quoted 10 lines · Stephen Warren
Quoted 9 lines · Joseph Lo
The power up sequence is different on the cold boot CPU and the CPU that resumed from the hotplug. For the cold boot CPU, it was been power gated as default. To power up the cold boot CPU, the power should be un-gated by un toggling the power gate register manually.
For the CPU that resumed from the hotplug, after un-halted the CPU. The flow controller will un-gate the power of the CPU. No need to manually control, just wait the power be resumed and continue the power up sequence after the CPU power is ready.

...

Quoted 8 lines

Quoted 5 lines
Also, it'd be good to explain (or at least briefly reference) the boot path for a cold-boot CPU and a warm boot CPU; I assume that somehow a cold boot CPU doesn't execute tegra_secondary_init(), but a warm boot CPU does?
The boot path was the same. Both of the conditions were booted from tegra_boot_secondary. Just the power sequence has been different. We add the code to recover the power up sequence of warm boot CPU.

Ah, I see - tegra20_power_up_cpu() runs first to boot the secondary CPU, and tegra_secondary_init() runs on the secondary CPU during the boot process, which then sets tegra_cpu_init_mask which influences what tegra20_power_up_cpu() does next time around. It'd be useful to say that in the patch description.

Peter De Schrijver

2013-01-02 12:15 UTC #4 lore raw

PATCH 1/1 ARM: tegra30: fix power up sequence for boot_secondary

In reply to Joseph Lo

Quoted 10 lines · Joseph Lo

The power up sequence is different on the cold boot CPU and the CPU that resumed from the hotplug. For the cold boot CPU, it was been power gated as default. To power up the cold boot CPU, the power should be un-gated by un toggling the power gate register manually.
For the CPU that resumed from the hotplug, after un-halted the CPU. The flow controller will un-gate the power of the CPU. No need to manually control, just wait the power be resumed and continue the power up sequence after the CPU power is ready.

Quoted 4 lines

Based on the work by:
Varun Wadekar <[email protected]>
Signed-off-by Joseph Lo <[email protected]>

Acked-by Peter De Schrijver <[email protected]>