Re: [PATCH 2/2] ARM: local timers: add timer support using IO mapped register

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


On 8/10/2012 5:58 PM, Rohit Vaswani wrote:
The current arch_timer only support accessing through CP15 interface.
Add support for ARM processors that only support IO mapped register
interface


It looks like this patch attempts to address both (a) non-percpu arch timers, and (b) memory mapped arch timers in one go. These should probably be broken out into two distinct logical changes.

More below...

Signed-off-by: Rohit Vaswani <rvaswani@xxxxxxxxxxxxxx>
---
  .../devicetree/bindings/arm/arch_timer.txt         |    7 +
  arch/arm/kernel/arch_timer.c                       |  259 ++++++++++++++++----
  2 files changed, 223 insertions(+), 43 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt
index 52478c8..1c71799 100644
--- a/Documentation/devicetree/bindings/arm/arch_timer.txt
+++ b/Documentation/devicetree/bindings/arm/arch_timer.txt
@@ -14,6 +14,13 @@ The timer is attached to a GIC to deliver its per-processor interrupts.

  - clock-frequency : The frequency of the main counter, in Hz. Optional.

+- irq-is-not-percpu: Specify is the timer irq is *NOT* a percpu (PPI) interrupt
+  In the default case i.e without this property, the timer irq is treated as a
+  PPI interrupt. Optional.
+

The handling of non-percpu IRQs looks broken. The code does (enable/disable)_percpu_irq() on IRQs that may no longer be percpu.

+- If the node address and reg is specified, the arch_timer will try to use the memory
+  mapped timer. Optional.
+
  Example:

  	timer {
diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
index 1d0d9df..09604b7 100644
--- a/arch/arm/kernel/arch_timer.c
+++ b/arch/arm/kernel/arch_timer.c
@@ -18,6 +18,7 @@
  #include <linux/clockchips.h>
  #include <linux/interrupt.h>
  #include <linux/of_irq.h>
+#include <linux/of_address.h>
  #include <linux/io.h>

  #include <asm/cputype.h>
@@ -29,8 +30,17 @@
  static unsigned long arch_timer_rate;
  static int arch_timer_ppi;
  static int arch_timer_ppi2;
+static int is_irq_percpu;

  static struct clock_event_device __percpu **arch_timer_evt;
+static void __iomem *timer_base;
+

Are percpu memory mapped arch timers an impossibility?

+struct arch_timer_operations {
+	void (*reg_write)(int, u32);
+	u32 (*reg_read)(int);
+	cycle_t (*get_cntpct)(void);
+	cycle_t (*get_cntvct)(void);
+};

  /*
   * Architected system timer support.
@@ -44,7 +54,29 @@ static struct clock_event_device __percpu **arch_timer_evt;
  #define ARCH_TIMER_REG_FREQ		1
  #define ARCH_TIMER_REG_TVAL		2

-static void arch_timer_reg_write(int reg, u32 val)
+/* Iomapped Register Offsets */
+#define ARCH_TIMER_CNTP_LOW_REG		0x000
+#define ARCH_TIMER_CNTP_HIGH_REG	0x004
+#define ARCH_TIMER_CNTV_LOW_REG		0x008
+#define ARCH_TIMER_CNTV_HIGH_REG	0x00C
+#define ARCH_TIMER_CTRL_REG		0x02C
+#define ARCH_TIMER_FREQ_REG		0x010
+#define ARCH_TIMER_CNTP_TVAL_REG	0x028
+#define ARCH_TIMER_CNTV_TVAL_REG	0x038
+

ARCH_TIMER_CNTV_TVAL_REG appears to be unused here.

+static void timer_reg_write_mem(int reg, u32 val)
+{
+	switch (reg) {
+	case ARCH_TIMER_REG_CTRL:
+		__raw_writel(val, timer_base + ARCH_TIMER_CTRL_REG);
+		break;
+	case ARCH_TIMER_REG_TVAL:
+		__raw_writel(val, timer_base + ARCH_TIMER_CNTP_TVAL_REG);
+		break;
+	}
+}
+

Wouldn't an array of offsets to map from ARCH_TIMER_REG_* to these memory mapped registers eliminate the need to switch-case your way through each register?

+static void timer_reg_write_cp15(int reg, u32 val)
  {
  	switch (reg) {
  	case ARCH_TIMER_REG_CTRL:
@@ -58,7 +90,28 @@ static void arch_timer_reg_write(int reg, u32 val)
  	isb();
  }

-static u32 arch_timer_reg_read(int reg)
+static u32 timer_reg_read_mem(int reg)
+{
+	u32 val;
+
+	switch (reg) {
+	case ARCH_TIMER_REG_CTRL:
+		val = __raw_readl(timer_base + ARCH_TIMER_CTRL_REG);
+		break;
+	case ARCH_TIMER_REG_FREQ:
+		val = __raw_readl(timer_base + ARCH_TIMER_FREQ_REG);
+		break;
+	case ARCH_TIMER_REG_TVAL:
+		val = __raw_readl(timer_base + ARCH_TIMER_CNTP_TVAL_REG);
+		break;
+	default:
+		BUG();
+	}
+
+	return val;
+}
+

Same as above.

+static u32 timer_reg_read_cp15(int reg)
  {
  	u32 val;

@@ -79,6 +132,103 @@ static u32 arch_timer_reg_read(int reg)
  	return val;
  }

+static cycle_t arch_counter_get_cntpct_mem(void)
+{
+	u32 cvall, cvalh, thigh;
+
+	do {
+		cvalh = __raw_readl(timer_base + ARCH_TIMER_CNTP_HIGH_REG);
+		cvall = __raw_readl(timer_base + ARCH_TIMER_CNTP_LOW_REG);
+		thigh = __raw_readl(timer_base + ARCH_TIMER_CNTP_HIGH_REG);
+	} while (cvalh != thigh);
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+
+static cycle_t arch_counter_get_cntpct_cp15(void)
+{
+	u32 cvall, cvalh;
+
+	asm volatile("mrrc p15, 0, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+
+static cycle_t arch_counter_get_cntvct_mem(void)
+{
+	u32 cvall, cvalh, thigh;
+
+	do {
+		cvalh = __raw_readl(timer_base + ARCH_TIMER_CNTV_HIGH_REG);
+		cvall = __raw_readl(timer_base + ARCH_TIMER_CNTV_LOW_REG);
+		thigh = __raw_readl(timer_base + ARCH_TIMER_CNTV_HIGH_REG);
+	} while (cvalh != thigh);
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+

Repetitive - the logic is identical to arch_counter_get_cntpct_mem() above.

+static cycle_t arch_counter_get_cntvct_cp15(void)
+{
+	u32 cvall, cvalh;
+
+	asm volatile("mrrc p15, 1, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+
+static struct arch_timer_operations arch_timer_ops_cp15 = {
+	.reg_read = &timer_reg_read_cp15,
+	.reg_write = &timer_reg_write_cp15,
+	.get_cntpct = &arch_counter_get_cntpct_cp15,
+	.get_cntvct = &arch_counter_get_cntvct_cp15,
+};
+
+static struct arch_timer_operations arch_timer_ops_mem = {
+	.reg_read = &timer_reg_read_mem,
+	.reg_write = &timer_reg_write_mem,
+	.get_cntpct = &arch_counter_get_cntpct_mem,
+	.get_cntvct = &arch_counter_get_cntvct_mem,
+};
+
+static struct arch_timer_operations *arch_specific_timer = &arch_timer_ops_cp15;
+
+static inline void arch_timer_reg_write(int reg, u32 val)
+{
+	arch_specific_timer->reg_write(reg, val);
+}
+
+static inline u32 arch_timer_reg_read(int reg)
+{
+	return arch_specific_timer->reg_read(reg);
+}
+
+static inline cycle_t arch_counter_get_cntpct(void)
+{
+	return arch_specific_timer->get_cntpct();
+}
+
+static inline cycle_t arch_counter_get_cntvct(void)
+{
+	return arch_specific_timer->get_cntvct();
+}
+

The 4 pointer chasers above could lose some verbosity by being #defines.

+static u32 notrace arch_counter_get_cntvct32(void)
+{
+	cycle_t cntvct = arch_counter_get_cntpct();

Shouldn't that be arch_counter_get_cntvct() instead?

+
+	/*
+	 * The sched_clock infrastructure only knows about counters
+	 * with at most 32bits. Forget about the upper 24 bits for the
+	 * time being...
+	 */
+	return (u32)(cntvct & (u32)~0);
+}
+
+static cycle_t arch_counter_read(struct clocksource *cs)
+{
+	return arch_counter_get_cntpct();
+}
+

Did the code really need to be moved around? Some of the functions in this file appear to be entirely unchanged, but show up as both added and removed lines.

  static irqreturn_t arch_timer_handler(int irq, void *dev_id)
  {
  	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
@@ -167,7 +317,9 @@ static int arch_timer_available(void)
  {
  	unsigned long freq;

-	if (!local_timer_is_architected())
+	if (timer_base)
+		arch_specific_timer = &arch_timer_ops_mem;
+	else if (!local_timer_is_architected())
  		return -ENXIO;

  	if (arch_timer_rate == 0) {
@@ -188,41 +340,6 @@ static int arch_timer_available(void)
  	return 0;
  }

-static inline cycle_t arch_counter_get_cntpct(void)
-{
-	u32 cvall, cvalh;
-
-	asm volatile("mrrc p15, 0, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
-
-	return ((cycle_t) cvalh << 32) | cvall;
-}
-
-static inline cycle_t arch_counter_get_cntvct(void)
-{
-	u32 cvall, cvalh;
-
-	asm volatile("mrrc p15, 1, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
-
-	return ((cycle_t) cvalh << 32) | cvall;
-}
-
-static u32 notrace arch_counter_get_cntvct32(void)
-{
-	cycle_t cntvct = arch_counter_get_cntvct();
-
-	/*
-	 * The sched_clock infrastructure only knows about counters
-	 * with at most 32bits. Forget about the upper 24 bits for the
-	 * time being...
-	 */
-	return (u32)(cntvct & (u32)~0);
-}
-
-static cycle_t arch_counter_read(struct clocksource *cs)
-{
-	return arch_counter_get_cntpct();
-}
-
  static struct clocksource clocksource_counter = {
  	.name	= "arch_sys_counter",
  	.rating	= 400,
@@ -262,8 +379,12 @@ static int __init arch_timer_register(void)

  	clocksource_register_hz(&clocksource_counter, arch_timer_rate);

-	err = request_percpu_irq(arch_timer_ppi, arch_timer_handler,
+	if (is_irq_percpu)
+		err = request_percpu_irq(arch_timer_ppi, arch_timer_handler,
  				 "arch_timer", arch_timer_evt);
+	else
+		err = request_irq(arch_timer_ppi, arch_timer_handler, 0,
+			"arch_timer", arch_timer_evt);
  	if (err) {
  		pr_err("arch_timer: can't register interrupt %d (%d)\n",
  		       arch_timer_ppi, err);
@@ -271,8 +392,13 @@ static int __init arch_timer_register(void)
  	}

  	if (arch_timer_ppi2) {
-		err = request_percpu_irq(arch_timer_ppi2, arch_timer_handler,
-					 "arch_timer", arch_timer_evt);
+		if (is_irq_percpu)
+			err = request_percpu_irq(arch_timer_ppi2,
+					arch_timer_handler, "arch_timer",
+					arch_timer_evt);
+		else
+			err = request_irq(arch_timer_ppi2, arch_timer_handler,
+					0, "arch_timer", arch_timer_evt);
  		if (err) {
  			pr_err("arch_timer: can't register interrupt %d (%d)\n",
  			       arch_timer_ppi2, err);
@@ -314,10 +440,40 @@ static const struct of_device_id arch_timer_of_match[] __initconst = {
  	{},
  };

+static int __init arch_timer_base_init(void)
+{
+	struct device_node *np;
+
+	if (!timer_base) {
+		np = of_find_matching_node(NULL, arch_timer_of_match);
+		if (!np) {
+			pr_err("arch_timer: can't find DT node\n");
+			return -ENODEV;
+		}
+
+		if (of_get_address(np, 0, NULL, NULL)) {
+			timer_base = of_iomap(np, 0);
+			if (!timer_base) {
+				pr_err("arch_timer: cant map timer base\n");
+				return -ENOMEM;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static inline void __init arch_timer_base_free(void)
+{
+	if (timer_base)
+		iounmap(timer_base);
+}
+
  int __init arch_timer_of_register(void)
  {
  	struct device_node *np;
  	u32 freq;
+	int ret;

  	np = of_find_matching_node(NULL, arch_timer_of_match);
  	if (!np) {
@@ -331,20 +487,37 @@ int __init arch_timer_of_register(void)

  	arch_timer_ppi = irq_of_parse_and_map(np, 0);
  	arch_timer_ppi2 = irq_of_parse_and_map(np, 1);
+
+	ret = arch_timer_base_init();
+	if (ret)
+		return ret;
+
+	is_irq_percpu = !(of_property_read_bool(np, "irq-is-not-percpu"));
+
  	pr_info("arch_timer: found %s irqs %d %d\n",
  		np->name, arch_timer_ppi, arch_timer_ppi2);

-	return arch_timer_register();
+	ret = arch_timer_register();
+	if (ret)
+		arch_timer_base_free();
+
+	return ret;
  }

  int __init arch_timer_sched_clock_init(void)
  {
  	int err;

-	err = arch_timer_available();
+	err = arch_timer_base_init();
  	if (err)
  		return err;

+	err = arch_timer_available();
+	if (err) {
+		arch_timer_base_free();
+		return err;
+	}
+
  	setup_sched_clock(arch_counter_get_cntvct32, 32, arch_timer_rate);
  	return 0;
  }


--
Cheers
- Cyril
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/


[Other Archives]     [Linux Kernel Newbies]     [Linux Driver Development]     [Linux Kbuild]     [Fedora Kernel]     [Linux Kernel Testers]     [Linux SH]     [Linux Omap]     [Linux Tape]     [Linux Input]     [Linux LEDS]     [Linux Kernel Janitors]     [Linux Kernel Packagers]     [Linux Doc]     [Linux Man Pages]     [Linux API]     [Linux Memory Management]     [Linux Modules]     [Linux Standards]     [Kernel Announce]     [Netdev]     [Git]     [Linux PCI]     Linux CAN Development     [Linux I2C]     [Linux RDMA]     [Linux NUMA]     [Netfilter]     [Netfilter Devel]     [SELinux]     [Bugtraq]     [FIO]     [Linux Perf Users]     [Linux Serial]     [Linux PPP]     [Linux ISDN]     [Linux Next]     [Kernel Stable Commits]     [Linux Tip Commits]     [Kernel MM Commits]     [Linux Security Module]     [AutoFS]     [Filesystem Development]     [Ext3 Filesystem]     [Linux bcache]     [Ext4 Filesystem]     [Linux BTRFS]     [Linux CEPH Filesystem]     [Linux XFS]     [XFS]     [Linux NFS]     [Linux CIFS]     [Ecryptfs]     [Linux NILFS]     [Linux Cachefs]     [Reiser FS]     [Initramfs]     [Linux FB Devel]     [Linux OpenGL]     [DRI Devel]     [Fastboot]     [Linux RT Users]     [Linux RT Stable]     [eCos]     [Corosync]     [Linux Clusters]     [LVS Devel]     [Hot Plug]     [Linux Virtualization]     [KVM]     [KVM PPC]     [KVM ia64]     [Linux Containers]     [Linux Hexagon]     [Linux Cgroups]     [Util Linux]     [Wireless]     [Linux Bluetooth]     [Bluez Devel]     [Ethernet Bridging]     [Embedded Linux]     [Barebox]     [Linux MMC]     [Linux IIO]     [Sparse]     [Smatch]     [Linux Arch]     [x86 Platform Driver]     [Linux ACPI]     [Linux IBM ACPI]     [LM Sensors]     [CPU Freq]     [Linux Power Management]     [Linmodems]     [Linux DCCP]     [Linux SCTP]     [ALSA Devel]     [Linux USB]     [Linux PA RISC]     [Linux Samsung SOC]     [MIPS Linux]     [IBM S/390 Linux]     [ARM Linux]     [ARM Kernel]     [ARM MSM]     [Tegra Devel]     [Sparc Linux]     [Linux Security]     [Linux Sound]     [Linux Media]     [Video 4 Linux]     [Linux IRDA Users]     [Linux for the blind]     [Linux RAID]     [Linux ATA RAID]     [Device Mapper]     [Linux SCSI]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Linux IDE]     [Linux SMP]     [Linux AXP]     [Linux Alpha]     [Linux M68K]     [Linux ia64]     [Linux 8086]     [Linux x86_64]     [Linux Config]     [Linux Apps]     [Linux MSDOS]     [Linux X.25]     [Linux Crypto]     [DM Crypt]     [Linux Trace Users]     [Linux Btrace]     [Linux Watchdog]     [Utrace Devel]     [Linux C Programming]     [Linux Assembly]     [Dash]     [DWARVES]     [Hail Devel]     [Linux Kernel Debugger]     [Linux gcc]     [Gcc Help]     [X.Org]     [Wine]

Add to Google Powered by Linux

[Older Kernel Discussion]     [Yosemite National Park Forum]     [Large Format Photos]     [Gimp]     [Yosemite Photos]     [Stuff]