[RFC] omap:

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Hi,

We are introducing a kernel driver for hardware spinlock, called hwspinlock.
It is designed to interface with the OMAP4 hardware spinlock module.  This
driver supports:
- Reserved spinlocks for internal use
- Dynamic allocation of unreserved locks
- Lock, unlock, and trylock functions, with or without disabling irqs/preempt
- Registered as a platform device driver

The device initialization will set aside some spinlocks as reserved for
special-purpose use.  All other locks can be used by anyone.  This is
configurable using a Kconfig option.  The device initialization file is:
                arch/arm/mach-omap2/hwspinlocks.c

The driver takes in data passed in device initialization.  The function
hwspinlock_probe() initializes the array of spinlock structures, each
containing a spinlock register address provided by the device initialization.
The device driver file is:
                arch/arm/plat-omap/hwspinlock.c

Here's an API summary:
int hwspinlock_lock(struct hwspinlock *);
        Attempt to lock a hardware spinlock.  If it is busy, the function will
        keep trying until it succeeds.  This is a blocking function.
int hwspinlock_trylock(struct hwspinlock *);
        Attempt to lock a hardware spinlock.  If it is busy, the function will
        return BUSY.  If it succeeds in locking, the function will return
        ACQUIRED.  This is a non-blocking function
int hwspinlock_unlock(struct hwspinlock *);
        Unlock a hardware spinlock.

int hwspinlock_lock_irqsave(struct hwspinlock *, unsigned long *);
        Same as hwspinlock_lock, but disables interrupts and preemption
int hwspinlock_trylock_irqsave(struct hwspinlock *, unsigned long *);
        Same as hwspinlock_trylock, but disables interrupts and preemption
int hwspinlock_unlock_irqrestore(struct hwspinlock *, unsigned long);
        Same as hwspinlock_unlock, but restores interrupts and preemption

struct hwspinlock *hwspinlock_request(void);
        Provides for "dynamic allocation" of an unreserved hardware spinlock.
        If no more locks are available, returns NULL.
struct hwspinlock *hwspinlock_request_specific(unsigned int);
        Provides for "static allocation" of a reserved hardware spinlock. This
        allows the system to use a specific reserved lock, identified by an ID.
        If the ID is invalid or if the desired lock is already allocated, this
        will return NULL.
int hwspinlock_free(struct hwspinlock *);
        Frees an allocated hardware spinlock (either reserved or unreserved).

Please see the below patch contents, or the attached patch, and provide feedback.

Signed-off-by: Simon Que <sque@xxxxxx>
Cc: Hari Kanigeri <h-kanigeri2@xxxxxx>

=====================================================================

diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
index 9f73d79..a13c188 100644
--- a/arch/arm/mach-omap2/Kconfig
+++ b/arch/arm/mach-omap2/Kconfig
@@ -182,3 +182,13 @@ config OMAP3_SDRC_AC_TIMING
          wish to say no.  Selecting yes without understanding what is
          going on could result in system crashes;

+config OMAP_HWSPINLOCK_NUM_RESERVED
+       int "Number of hardware spinlocks reserved for system use"
+       depends on ARCH_OMAP
+       default 8
+       range 0 32
+       help
+         Choose a number of hardware spinlocks to reserve for internal use.
+         The rest will be unreserved and availble for general use.  Make
+         that the number of reserved locks does not exceed the total number
+         available locks.
diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index 6725b3a..14af19a 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -170,3 +170,5 @@ obj-y                                       += $(nand-m) $(nand-y)

 smc91x-$(CONFIG_SMC91X)                        := gpmc-smc91x.o
 obj-y                                  += $(smc91x-m) $(smc91x-y)
+
+obj-y                                  += hwspinlocks.o
\ No newline at end of file
diff --git a/arch/arm/mach-omap2/hwspinlocks.c b/arch/arm/mach-omap2/hwspinlocks.c
new file mode 100644
index 0000000..de813a0
--- /dev/null
+++ b/arch/arm/mach-omap2/hwspinlocks.c
@@ -0,0 +1,126 @@
+/*
+ * OMAP hardware spinlock driver
+ *
+ * Copyright (C) 2010 Texas Instruments. All rights reserved.
+ *
+ * Contact: Simon Que <sque@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+#include <plat/hwspinlock.h>
+
+/* Base address of HW spinlock module */
+#define HWSPINLOCK_BASE                (L4_44XX_BASE + 0xF6000)
+#define HWSPINLOCK_REGADDR(reg)                                \
+                       OMAP2_L4_IO_ADDRESS(HWSPINLOCK_BASE + (reg))
+
+/* Spinlock register offsets */
+#define HWSPINLOCK_REVISION                    0x0000
+#define HWSPINLOCK_SYSCONFIG                   0x0010
+#define HWSPINLOCK_SYSSTATUS                   0x0014
+#define HWSPINLOCK_LOCK_BASE                   0x0800
+
+/* Spinlock register addresses */
+#define HWSPINLOCK_REVISION_REG                        \
+       HWSPINLOCK_REGADDR(HWSPINLOCK_REVISION)
+#define HWSPINLOCK_SYSCONFIG_REG                       \
+       HWSPINLOCK_REGADDR(HWSPINLOCK_SYSCONFIG)
+#define HWSPINLOCK_SYSSTATUS_REG                       \
+       HWSPINLOCK_REGADDR(HWSPINLOCK_SYSSTATUS)
+#define HWSPINLOCK_LOCK_REG(i)                 \
+       HWSPINLOCK_REGADDR(HWSPINLOCK_LOCK_BASE + 0x4 * (i))
+
+/* Spinlock count code */
+#define HWSPINLOCK_32_REGS                             1
+#define HWSPINLOCK_64_REGS                             2
+#define HWSPINLOCK_128_REGS                            4
+#define HWSPINLOCK_256_REGS                            8
+#define HWSPINLOCK_NUMLOCKS_OFFSET                     24
+
+
+/* Initialization function */
+int __init hwspinlocks_init(void)
+{
+       int i;
+       int retval = 0;
+
+       struct platform_device *pdev;
+       struct hwspinlock_plat_info *pdata;
+       void __iomem *base;
+       int num_locks;
+       bool is_reserved;
+
+       /* Determine number of locks */
+       switch (__raw_readl(HWSPINLOCK_SYSSTATUS_REG) >>
+                                       HWSPINLOCK_NUMLOCKS_OFFSET) {
+       case HWSPINLOCK_32_REGS:
+               num_locks = 32;
+               break;
+       case HWSPINLOCK_64_REGS:
+               num_locks = 64;
+               break;
+       case HWSPINLOCK_128_REGS:
+               num_locks = 128;
+               break;
+       case HWSPINLOCK_256_REGS:
+               num_locks = 256;
+               break;
+       default:
+               return -EINVAL; /* Invalid spinlock count code */
+       }
+
+       /* Device drivers */
+       for (i = 0; i < num_locks; i++) {
+               pdev = platform_device_alloc("hwspinlock", i);
+
+               base = HWSPINLOCK_LOCK_REG(i);  /* Get register address */
+
+               /* Some locks are reserved for system use */
+               if (i < CONFIG_OMAP_HWSPINLOCK_NUM_RESERVED)
+                       is_reserved = true;
+               else
+                       is_reserved = false;
+
+               /* Pass data to device initialization */
+               pdata = kzalloc(sizeof(struct hwspinlock_plat_info),
+                                                               GFP_KERNEL);
+               pdata->num_locks = num_locks;
+               pdata->io_base = base;
+               pdata->is_reserved = is_reserved;
+               retval = platform_device_add_data(pdev, pdata, sizeof(*pdata));
+               if (retval)
+                       goto device_add_fail;
+
+               retval = platform_device_add(pdev);
+               if (retval)
+                       goto device_add_fail;
+               continue;
+device_add_fail:
+               platform_device_put(pdev);
+       }
+
+       return retval;
+}
+module_init(hwspinlocks_init);
+
diff --git a/arch/arm/plat-omap/Makefile b/arch/arm/plat-omap/Makefile
index a37abf5..fb98ff9 100644
--- a/arch/arm/plat-omap/Makefile
+++ b/arch/arm/plat-omap/Makefile
@@ -32,4 +32,5 @@ obj-y += $(i2c-omap-m) $(i2c-omap-y)
 obj-$(CONFIG_OMAP_MBOX_FWK) += mailbox.o
 obj-$(CONFIG_OMAP_REMOTE_PROC) += remoteproc.o

-obj-$(CONFIG_OMAP_PM_NOOP) += omap-pm-noop.o
\ No newline at end of file
+obj-$(CONFIG_OMAP_PM_NOOP) += omap-pm-noop.o
+obj-y += hwspinlock.o
\ No newline at end of file
diff --git a/arch/arm/plat-omap/hwspinlock.c b/arch/arm/plat-omap/hwspinlock.c
new file mode 100644
index 0000000..327a524
--- /dev/null
+++ b/arch/arm/plat-omap/hwspinlock.c
@@ -0,0 +1,331 @@
+/*
+ * OMAP hardware spinlock driver
+ *
+ * Copyright (C) 2010 Texas Instruments. All rights reserved.
+ *
+ * Contact: Simon Que <sque@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <plat/hwspinlock.h>
+
+/* for managing a hardware spinlock module */
+struct hwspinlock_state {
+       bool is_init;                   /* For first-time initialization */
+       int num_locks;                  /* Total number of locks in system */
+       spinlock_t local_lock;          /* Local protection */
+};
+
+/* Points to the hardware spinlock module */
+static struct hwspinlock_state hwspinlock_state;
+static struct hwspinlock_state *hwspinlock_module = &hwspinlock_state;
+
+/* Spinlock object */
+struct hwspinlock {
+       void __iomem *io_base;
+       bool is_reserved;
+       bool is_allocated;
+       struct platform_device *pdev;
+};
+
+/* Array of spinlocks */
+static struct hwspinlock *hwspinlocks;
+
+/* API functions */
+
+/* Busy loop to acquire a spinlock */
+int hwspinlock_lock(struct hwspinlock *handle)
+{
+       int retval;
+
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       if (WARN_ON(in_atomic() || in_irq()))
+               return -EPERM;
+
+       /* Attempt to acquire the lock by reading from it */
+       do {
+               retval = __raw_readl(handle->io_base);
+       } while (retval == HWSPINLOCK_BUSY);
+
+       return 0;
+}
+EXPORT_SYMBOL(hwspinlock_lock);
+
+/* Attempt to acquire a spinlock once */
+int hwspinlock_trylock(struct hwspinlock *handle)
+{
+       int retval = 0;
+
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       if (WARN_ON(in_atomic() || in_irq()))
+               return -EPERM;
+
+       /* Attempt to acquire the lock by reading from it */
+       retval = __raw_readl(handle->io_base);
+
+       return retval;
+}
+EXPORT_SYMBOL(hwspinlock_trylock);
+
+/* Release a spinlock */
+int hwspinlock_unlock(struct hwspinlock *handle)
+{
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       /* Release it by writing 0 to it */
+       __raw_writel(0, handle->io_base);
+
+       return 0;
+}
+EXPORT_SYMBOL(hwspinlock_unlock);
+
+/* Busy loop to acquire a spinlock, disabling interrupts/preemption */
+int hwspinlock_lock_irqsave(struct hwspinlock *handle, unsigned long *flags)
+{
+       int retval;
+       unsigned long temp_flags;
+
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       if (WARN_ON(in_atomic() || in_irq()))
+               return -EPERM;
+
+       if (WARN_ON(flags == NULL))
+               return -EINVAL;
+
+       /* Attempt to acquire the lock by reading from it */
+       do {
+               preempt_disable();                      /* Disable preemption */
+               local_irq_save(temp_flags);             /* Disable interrupts */
+
+               retval = __raw_readl(handle->io_base);
+
+               /* Restore interrupts and preemption if not successful */
+               if (retval == HWSPINLOCK_BUSY) {
+                       local_irq_restore(temp_flags);
+                       preempt_enable();
+               }
+       } while (retval == HWSPINLOCK_BUSY);
+
+       *flags = temp_flags;            /* Return IRQ state */
+
+       return 0;
+}
+EXPORT_SYMBOL(hwspinlock_lock_irqsave);
+
+/* Attempt to acquire a spinlock once, disabling interrupts/preemption */
+int hwspinlock_trylock_irqsave(struct hwspinlock *handle, unsigned long *flags)
+{
+       int retval = 0;
+       unsigned long temp_flags;
+
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       if (WARN_ON(in_atomic() || in_irq()))
+               return -EPERM;
+
+       if (WARN_ON(flags == NULL))
+               return -EINVAL;
+
+       preempt_disable();                      /* Disable preemption */
+       local_irq_save(temp_flags);             /* Disable interrupts */
+
+       /* Attempt to acquire the lock by reading from it */
+       retval = __raw_readl(handle->io_base);
+
+       /* Restore interrupts and preemption if not successful */
+       if (retval == HWSPINLOCK_BUSY) {
+               local_irq_restore(temp_flags);
+               preempt_enable();
+       } else
+               *flags = temp_flags;    /* Return IRQ state */
+
+       return retval;
+}
+EXPORT_SYMBOL(hwspinlock_trylock_irqsave);
+
+/* Unlock a spinlock that was locked with irq/preempt disabled */
+int hwspinlock_unlock_irqrestore(struct hwspinlock *handle, unsigned long
+                                                                       flags)
+{
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       /* Release it by writing 0 to it */
+       __raw_writel(0, handle->io_base);
+
+       /* Restore interrupts and preemption */
+       local_irq_restore(flags);
+       preempt_enable();
+
+       return 0;
+}
+EXPORT_SYMBOL(hwspinlock_unlock_irqrestore);
+
+/* Request an unclaimed spinlock */
+struct hwspinlock *hwspinlock_request(void)
+{
+       int i;
+       bool found = false;
+       struct hwspinlock *handle = NULL;
+       unsigned long flags;
+
+       spin_lock_irqsave(&hwspinlock_module->local_lock, flags);
+       /* Search for an unclaimed, unreserved lock */
+       for (i = 0; i < hwspinlock_module->num_locks && !found; i++) {
+               if (!hwspinlocks[i].is_allocated &&
+                                               !hwspinlocks[i].is_reserved) {
+                       found = true;
+                       handle = &hwspinlocks[i];
+               }
+       }
+       spin_unlock_irqrestore(&hwspinlock_module->local_lock, flags);
+
+       /* Return error if no more locks available */
+       if (!found)
+               return NULL;
+
+       handle->is_allocated = true;
+
+       return handle;
+}
+EXPORT_SYMBOL(hwspinlock_request);
+
+/* Request an unclaimed spinlock by ID */
+struct hwspinlock *hwspinlock_request_specific(unsigned int id)
+{
+       struct hwspinlock *handle = NULL;
+       unsigned long flags;
+
+       spin_lock_irqsave(&hwspinlock_module->local_lock, flags);
+
+       if (WARN_ON(!hwspinlocks[id].is_reserved))
+               goto exit;
+
+       if (WARN_ON(hwspinlocks[id].is_allocated))
+               goto exit;
+
+       handle = &hwspinlocks[id];
+       handle->is_allocated = true;
+
+exit:
+       spin_unlock_irqrestore(&hwspinlock_module->local_lock, flags);
+       return handle;
+}
+EXPORT_SYMBOL(hwspinlock_request_specific);
+
+/* Release a claimed spinlock */
+int hwspinlock_free(struct hwspinlock *handle)
+{
+       if (WARN_ON(handle == NULL))
+               return -EINVAL;
+
+       if (WARN_ON(!handle->is_allocated))
+               return -ENOMEM;
+
+       handle->is_allocated = false;
+
+       return 0;
+}
+EXPORT_SYMBOL(hwspinlock_free);
+
+/* Probe function */
+static int __devinit hwspinlock_probe(struct platform_device *pdev)
+{
+       struct hwspinlock_plat_info *pdata = pdev->dev.platform_data;
+       int id = pdev->id;
+
+       /* Set up the spinlock count and array */
+       if (!hwspinlock_module->is_init) {
+               hwspinlock_module->num_locks = pdata->num_locks;
+
+               /* Allocate spinlock device objects */
+               hwspinlocks = kmalloc(sizeof(struct hwspinlock) *
+                               hwspinlock_module->num_locks, GFP_KERNEL);
+               if (WARN_ON(hwspinlocks == NULL))
+                       return -ENOMEM;
+
+               /* Initialize local lock */
+               spin_lock_init(&hwspinlock_module->local_lock);
+
+               /* Only do initialization once */
+               hwspinlock_module->is_init = true;
+       }
+
+       hwspinlocks[id].pdev                    = pdev;
+
+       hwspinlocks[id].is_reserved             = pdata->is_reserved;
+       hwspinlocks[id].is_allocated            = false;
+       hwspinlocks[id].io_base                 = pdata->io_base;
+
+       return 0;
+}
+
+static struct platform_driver hwspinlock_driver = {
+       .probe          = hwspinlock_probe,
+       .driver         = {
+               .name   = "hwspinlock",
+       },
+};
+
+/* Initialization function */
+static int __init hwspinlock_init(void)
+{
+       int retval = 0;
+
+       /* Register spinlock driver */
+       retval = platform_driver_register(&hwspinlock_driver);
+
+       /* Make sure the it was properly initialized */
+       if (WARN_ON(!hwspinlock_module->is_init))
+               return -EACCES;
+
+       return retval;
+}
+
+/* Cleanup function */
+static void __exit hwspinlock_exit(void)
+{
+       platform_driver_unregister(&hwspinlock_driver);
+
+       /* Free spinlock device objects */
+       if (hwspinlock_module->is_init)
+               kfree(hwspinlocks);
+}
+
+module_init(hwspinlock_init);
+module_exit(hwspinlock_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Hardware spinlock driver");
+MODULE_AUTHOR("Simon Que");
+MODULE_AUTHOR("Hari Kanigeri");
diff --git a/arch/arm/plat-omap/include/plat/hwspinlock.h b/arch/arm/plat-omap/include/plat/hwspinlock.h
new file mode 100644
index 0000000..1cdf7a8
--- /dev/null
+++ b/arch/arm/plat-omap/include/plat/hwspinlock.h
@@ -0,0 +1,35 @@
+/* hwspinlock.h */
+
+#ifndef HWSPINLOCK_H
+#define HWSPINLOCK_H
+
+#include <linux/platform_device.h>
+#include <plat/omap44xx.h>
+
+/* Read values from the spinlock register */
+#define HWSPINLOCK_ACQUIRED 0
+#define HWSPINLOCK_BUSY 1
+
+/* Device data */
+struct hwspinlock_plat_info {
+       int num_locks;                  /* Number of locks (initialization) */
+       void __iomem *io_base;          /* Address of spinlock register */
+       bool is_reserved;               /* Reserved for system use? */
+};
+
+struct hwspinlock;
+
+int hwspinlock_lock(struct hwspinlock *handle);
+int hwspinlock_trylock(struct hwspinlock *handle);
+int hwspinlock_unlock(struct hwspinlock *handle);
+
+int hwspinlock_lock_irqsave(struct hwspinlock *handle, unsigned long *flags);
+int hwspinlock_trylock_irqsave(struct hwspinlock *handle, unsigned long *flags);
+int hwspinlock_unlock_irqrestore(struct hwspinlock *handle, unsigned long
+                                                                       flags);
+
+struct hwspinlock *hwspinlock_request(void);
+struct hwspinlock *hwspinlock_request_specific(unsigned int id);
+int hwspinlock_free(struct hwspinlock *hwspinlock_ptr);
+
+#endif /* HWSPINLOCK_H */
--
1.7.0

Attachment: 0001-omap-hwspinlock-Added-hwspinlock-driver.patch
Description: 0001-omap-hwspinlock-Added-hwspinlock-driver.patch


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