Patchwork [V3,1/3] ARM: tegra114: Reprogram GIC CPU interface to bypass IRQ on CPU PM entry

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Submitter Joseph Lo
Date June 25, 2013, 9:23 a.m.
Message ID <1372152242-16373-2-git-send-email-josephl@nvidia.com>
Download mbox | patch
Permalink /patch/254074/
State Superseded, archived
Headers show

Comments

Joseph Lo - June 25, 2013, 9:23 a.m.
There is a difference between GICv1 and v2 when CPU in power management
mode (aka CPU power down on Tegra). For GICv1, IRQ/FIQ interrupt lines
going to CPU are same lines which are also used for wake-interrupt.
Therefore, we cannot disable the GIC CPU interface if we need to use same
interrupts for CPU wake purpose. This creates a race condition for CPU
power off entry. Also, in GICv1, disabling GICv1 CPU interface puts GICv1
into bypass mode such that incoming legacy IRQ/FIQ are sent to CPU, which
means disabling GIC CPU interface doesn't really disable IRQ/FIQ to CPU.

GICv2 provides a wake IRQ/FIQ (for wake-event purpose), which are not
disabled by GIC CPU interface. This is done by adding a bypass override
capability when the interrupts are disabled at the CPU interface. To
support this, there are four bits about IRQ/FIQ BypassDisable in CPU
interface Control Register. When the IRQ/FIQ not being driver by the
CPU interface, each interrupt output signal can be deasserted rather
than being driven by the legacy interrupt input.

So the wake-event can be used as wakeup signals to SoC (system power
controller).

To prevent race conditions and ensure proper interrupt routing on
Cortex-A15 CPUs when they are power-gated, add a CPU PM notifier
call-back to reprogram the GIC CPU interface on PM entry. The
GIC CPU interface will be reset back to its normal state by
the common GIC CPU PM exit callback when the CPU wakes up.

Based on the work by: Scott Williams <scwilliams@nvidia.com>

Signed-off-by: Joseph Lo <josephl@nvidia.com>
---
V3:
* no change
V2:
* no change
---
 arch/arm/mach-tegra/irq.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
Stephen Warren - June 25, 2013, 11:02 p.m.
On 06/25/2013 03:23 AM, Joseph Lo wrote:
> There is a difference between GICv1 and v2 when CPU in power management
> mode (aka CPU power down on Tegra). For GICv1, IRQ/FIQ interrupt lines
> going to CPU are same lines which are also used for wake-interrupt.
> Therefore, we cannot disable the GIC CPU interface if we need to use same
> interrupts for CPU wake purpose. This creates a race condition for CPU
> power off entry. Also, in GICv1, disabling GICv1 CPU interface puts GICv1
> into bypass mode such that incoming legacy IRQ/FIQ are sent to CPU, which
> means disabling GIC CPU interface doesn't really disable IRQ/FIQ to CPU.
> 
> GICv2 provides a wake IRQ/FIQ (for wake-event purpose), which are not
> disabled by GIC CPU interface. This is done by adding a bypass override
> capability when the interrupts are disabled at the CPU interface. To
> support this, there are four bits about IRQ/FIQ BypassDisable in CPU
> interface Control Register. When the IRQ/FIQ not being driver by the
> CPU interface, each interrupt output signal can be deasserted rather
> than being driven by the legacy interrupt input.
> 
...
> diff --git a/arch/arm/mach-tegra/irq.c b/arch/arm/mach-tegra/irq.c

> +static int tegra_gic_notifier(struct notifier_block *self,
> +			      unsigned long cmd, void *v)
> +{
> +	switch (cmd) {
> +	case CPU_PM_ENTER:
> +		writel_relaxed(0x1E0, tegra_gic_cpu_base + GIC_CPU_CTRL);

I assume that 0x1e0 is the "four bits" for IRQ/FIQ bypass disable that
are mentioned in the commit description. are there #defines that can be
used instead of literal 0x1e0 here?
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Joseph Lo - June 26, 2013, 11:19 a.m.
On Wed, 2013-06-26 at 07:02 +0800, Stephen Warren wrote:
> On 06/25/2013 03:23 AM, Joseph Lo wrote:
> > There is a difference between GICv1 and v2 when CPU in power management
> > mode (aka CPU power down on Tegra). For GICv1, IRQ/FIQ interrupt lines
> > going to CPU are same lines which are also used for wake-interrupt.
> > Therefore, we cannot disable the GIC CPU interface if we need to use same
> > interrupts for CPU wake purpose. This creates a race condition for CPU
> > power off entry. Also, in GICv1, disabling GICv1 CPU interface puts GICv1
> > into bypass mode such that incoming legacy IRQ/FIQ are sent to CPU, which
> > means disabling GIC CPU interface doesn't really disable IRQ/FIQ to CPU.
> > 
> > GICv2 provides a wake IRQ/FIQ (for wake-event purpose), which are not
> > disabled by GIC CPU interface. This is done by adding a bypass override
> > capability when the interrupts are disabled at the CPU interface. To
> > support this, there are four bits about IRQ/FIQ BypassDisable in CPU
> > interface Control Register. When the IRQ/FIQ not being driver by the
> > CPU interface, each interrupt output signal can be deasserted rather
> > than being driven by the legacy interrupt input.
> > 
> ...
> > diff --git a/arch/arm/mach-tegra/irq.c b/arch/arm/mach-tegra/irq.c
> 
> > +static int tegra_gic_notifier(struct notifier_block *self,
> > +			      unsigned long cmd, void *v)
> > +{
> > +	switch (cmd) {
> > +	case CPU_PM_ENTER:
> > +		writel_relaxed(0x1E0, tegra_gic_cpu_base + GIC_CPU_CTRL);
> 
> I assume that 0x1e0 is the "four bits" for IRQ/FIQ bypass disable that
> are mentioned in the commit description. are there #defines that can be
> used instead of literal 0x1e0 here?

The common "arm-gic.h" didn't have the new define for GICv2 yet. So I
didn't define something like GIC_CPU_{FIQ,IRQ}BypDisGrp{0,1} for Tegra.

Thanks,
Joseph

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Patch

diff --git a/arch/arm/mach-tegra/irq.c b/arch/arm/mach-tegra/irq.c
index 0de4eed..1a74d56 100644
--- a/arch/arm/mach-tegra/irq.c
+++ b/arch/arm/mach-tegra/irq.c
@@ -18,10 +18,12 @@ 
  */
 
 #include <linux/kernel.h>
+#include <linux/cpu_pm.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/io.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/irqchip/arm-gic.h>
 #include <linux/syscore_ops.h>
 
@@ -65,6 +67,7 @@  static u32 cpu_ier[TEGRA_MAX_NUM_ICTLRS];
 static u32 cpu_iep[TEGRA_MAX_NUM_ICTLRS];
 
 static u32 ictlr_wake_mask[TEGRA_MAX_NUM_ICTLRS];
+static void __iomem *tegra_gic_cpu_base;
 #endif
 
 bool tegra_pending_sgi(void)
@@ -213,8 +216,43 @@  int tegra_legacy_irq_syscore_init(void)
 
 	return 0;
 }
+
+static int tegra_gic_notifier(struct notifier_block *self,
+			      unsigned long cmd, void *v)
+{
+	switch (cmd) {
+	case CPU_PM_ENTER:
+		writel_relaxed(0x1E0, tegra_gic_cpu_base + GIC_CPU_CTRL);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block tegra_gic_notifier_block = {
+	.notifier_call = tegra_gic_notifier,
+};
+
+static const struct of_device_id tegra114_dt_gic_match[] __initconst = {
+	{ .compatible = "arm,cortex-a15-gic" },
+	{ }
+};
+
+static void tegra114_gic_cpu_pm_registration(void)
+{
+	struct device_node *dn;
+
+	dn = of_find_matching_node(NULL, tegra114_dt_gic_match);
+	if (!dn)
+		return;
+
+	tegra_gic_cpu_base = of_iomap(dn, 1);
+
+	cpu_pm_register_notifier(&tegra_gic_notifier_block);
+}
 #else
 #define tegra_set_wake NULL
+static void tegra114_gic_cpu_pm_registration(void) { }
 #endif
 
 void __init tegra_init_irq(void)
@@ -252,4 +290,6 @@  void __init tegra_init_irq(void)
 	if (!of_have_populated_dt())
 		gic_init(0, 29, distbase,
 			IO_ADDRESS(TEGRA_ARM_PERIF_BASE + 0x100));
+
+	tegra114_gic_cpu_pm_registration();
 }