> -----Original Message-----
> From: linux-omap-ow...@vger.kernel.org
> [mailto:linux-omap-ow...@vger.kernel.org] On Behalf Of Kanigeri, Hari
> Sent: Monday, July 19, 2010 10:20 PM
> To: Linux Omap; Tony Lindgren
> Cc: Shilimkar, Santosh; Cousson, Benoit; Que, Simon; Kanigeri, Hari
> Subject: [PATCH 3/5] omap:hwspinlock-added hwspinlock driver
>
> From: Simon Que <s...@ti.com>
>
> Created driver for OMAP hardware spinlock. This driver supports:
> - Reserved spinlocks for internal use
[sp] How do we reserver the spinlocks? I didn't see any API or parameter
used to reserve them.
If this refers to hwspinlock_request_specific(), then it isn't
really reservation. Reservation is usually is blocks and I would
expect range input.
How is this reservation made known to other processors who would
be attempting to use these spinlocks - in a multi processor scenario
e.g. OMAP4. Both processors need to be aware of this "reservation".
> - 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 uses hwmod to configure the devices.
> One device will be created for each IP. It will pass
> spinlock register offset
> info to the driver. The device initialization file is:
> arch/arm/mach-omap2/hwspinlocks.c
>
> The driver takes in register offset info passed in device
> initialization.
> It uses hwmod to obtain the base address of the hardware
> spinlock module.
> Then it reads info from the registers. The function
> hwspinlock_probe()
> initializes the array of spinlock structures, each containing
> a spinlock
> register address calculated from the base address and lock offsets.
> 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.
>
> struct hwspinlock *hwspinlock_request(void);
> Provides for "dynamic allocation" of a hardware
> spinlock. It returns
> the handle to the next available (unallocated)
> spinlock. If no more
> locks are available, it returns NULL.
> struct hwspinlock *hwspinlock_request_specific(unsigned int);
> Provides for "static allocation" of a specific hardware
> spinlock. This
> allows the system to use a specific spinlock,
> identified by an ID. If
> the ID is invalid or if the desired lock is already
> allocated, this
> will return NULL. Otherwise it returns a spinlock handle.
> int hwspinlock_free(struct hwspinlock *);
> Frees an allocated hardware spinlock (either reserved
> or unreserved).
>
> Signed-off-by: Simon Que <s...@ti.com>
> Signed-off-by: Hari Kanigeri <h-kanige...@ti.com>
> ---
> arch/arm/mach-omap2/hwspinlocks.c | 70 ++++++
> arch/arm/plat-omap/hwspinlock.c | 335
> ++++++++++++++++++++++++++
> arch/arm/plat-omap/include/plat/hwspinlock.h | 29 +++
> 3 files changed, 434 insertions(+), 0 deletions(-)
> create mode 100644 arch/arm/mach-omap2/hwspinlocks.c
> create mode 100644 arch/arm/plat-omap/hwspinlock.c
> create mode 100644 arch/arm/plat-omap/include/plat/hwspinlock.h
>
> diff --git a/arch/arm/mach-omap2/hwspinlocks.c
> b/arch/arm/mach-omap2/hwspinlocks.c
> new file mode 100644
> index 0000000..f0f05e1
> --- /dev/null
> +++ b/arch/arm/mach-omap2/hwspinlocks.c
> @@ -0,0 +1,70 @@
> +/*
> + * OMAP hardware spinlock device initialization
> + *
> + * Copyright (C) 2010 Texas Instruments. All rights reserved.
> + *
> + * Contact: Simon Que <s...@ti.com>
> + *
> + * 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>
> +#include <plat/omap_device.h>
> +#include <plat/omap_hwmod.h>
> +
> +/* Spinlock register offsets */
> +#define REVISION_OFFSET 0x0000
[sp] Don't see this being used in the patch.
> +#define SYSCONFIG_OFFSET 0x0010
[sp] Ditto.
> +#define SYSSTATUS_OFFSET 0x0014
> +#define LOCK_BASE_OFFSET 0x0800
> +#define LOCK_OFFSET(i)
> (LOCK_BASE_OFFSET + 0x4 * (i))
> +
> +/* Initialization function */
> +int __init hwspinlocks_init(void)
> +{
> + int retval = 0;
> +
> + struct hwspinlock_plat_info *pdata;
> + struct omap_hwmod *oh;
> + char *oh_name, *pdev_name;
> +
> + oh_name = "spinlock";
> + oh = omap_hwmod_lookup(oh_name);
> + if (WARN_ON(oh == NULL))
> + return -EINVAL;
> +
> + pdev_name = "hwspinlock";
> +
> + /* Pass data to device initialization */
> + pdata = kzalloc(sizeof(struct hwspinlock_plat_info),
> GFP_KERNEL);
> + if (WARN_ON(pdata == NULL))
> + return -ENOMEM;
> + pdata->sysstatus_offset = SYSSTATUS_OFFSET;
> + pdata->lock_base_offset = LOCK_BASE_OFFSET;
> +
> + omap_device_build(pdev_name, 0, oh, pdata,
> + sizeof(struct hwspinlock_plat_info),
> NULL, 0, false);
> +
> + return retval;
> +}
> +module_init(hwspinlocks_init);
[sp] Why do we need a separate file for one function?
> diff --git a/arch/arm/plat-omap/hwspinlock.c
> b/arch/arm/plat-omap/hwspinlock.c
> new file mode 100644
> index 0000000..1883add
> --- /dev/null
> +++ b/arch/arm/plat-omap/hwspinlock.c
> @@ -0,0 +1,335 @@
> +/*
> + * OMAP hardware spinlock driver
> + *
> + * Copyright (C) 2010 Texas Instruments. All rights reserved.
> + *
> + * Contact: Simon Que <s...@ti.com>
> + *
> + * 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
> + *
> + * 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 uses hwmod to configure the
> devices. One device
> + * will be created for each IP. It will pass spinlock
> register offset info to
> + * the driver. The device initialization file is:
> + * arch/arm/mach-omap2/hwspinlocks.c
> + *
> + * The driver takes in register offset info passed in device
> initialization.
> + * It uses hwmod to obtain the base address of the hardware
> spinlock module.
> + * Then it reads info from the registers. The function
> hwspinlock_probe()
> + * initializes the array of spinlock structures, each
> containing a spinlock
> + * register address calculated from the base address and
> lock offsets.
> + *
> + * 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.
> + *
> + * struct hwspinlock *hwspinlock_request(void);
> + * Provides for "dynamic allocation" of a hardware
> spinlock. It returns
> + * the handle to the next available (unallocated)
> spinlock. If no more
> + * locks are available, it returns NULL.
> + * struct hwspinlock *hwspinlock_request_specific(unsigned int);
> + * Provides for "static allocation" of a specific
> hardware spinlock. This
> + * allows the system to use a specific spinlock,
> identified by an ID. If
> + * the ID is invalid or if the desired lock is already
> allocated, this
> + * will return NULL. Otherwise it returns a spinlock handle.
> + * int hwspinlock_free(struct hwspinlock *);
> + * Frees an allocated hardware spinlock (either
> reserved or unreserved).
> + */
> +
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#include <plat/hwspinlock.h>
> +
> +/* Spinlock count code */
> +#define SPINLOCK_32_REGS 1
> +#define SPINLOCK_64_REGS 2
> +#define SPINLOCK_128_REGS 4
> +#define SPINLOCK_256_REGS 8
> +#define SPINLOCK_NUMLOCKS_OFFSET 24
[sp] Shouldn't we combine this offset with other offset definitions?
> +
> +/* 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 */
> + void __iomem *io_base; /* Mapped base address */
> +};
[sp] The name seems to be misleading. The usage suggest that it
indicates the module state. We could use suffix _mod_state
or similar.
> +
> +/* Points to the hardware spinlock module */
> +static struct hwspinlock_state hwspinlock_state;
> +static struct hwspinlock_state *hwspinlock_module =
> &hwspinlock_state;
> +
> +/* Spinlock object */
> +struct hwspinlock {
> + bool is_init;
> + int id;
> + void __iomem *lock_reg;
> + bool is_allocated;
> + struct platform_device *pdev;
[sp] 2 different bools for "init" and "allocated" could be avoided
by a "state" field with possible values as xx_RESET, xx_INIT,
xx_ALLOC, ...
> +};
> +
> +/* Array of spinlocks */
> +static struct hwspinlock *hwspinlocks;
[sp] Do we really want to stress the compilers by making the
name of structure and variable to be same? This situation
is avoidable.
> +
> +/* 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_irq()))
> + return -EPERM;
> +
> + if (pm_runtime_get(&handle->pdev->dev) < 0)
> + return -ENODEV;
[sp] I may be missing discussions on this list; but
can you confirm if pm_runtime_get()/put() are
waiting to be merged on the master branch.
> +
> + /* Attempt to acquire the lock by reading from it */
> + do {
> + retval = readl(handle->lock_reg);
> + } while (retval == HWSPINLOCK_BUSY);
[sp] The description did say that call is blocking but this
tight-loop could lead to deadlock situations.
Do we intend it this way?
> +
> + 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_irq()))
> + return -EPERM;
[sp] Would be good to add a comment - why it is not permitted?
> +
> + if (pm_runtime_get(&handle->pdev->dev) < 0)
> + return -ENODEV;
> +
> + /* Attempt to acquire the lock by reading from it */
> + retval = readl(handle->lock_reg);
> +
> + if (retval == HWSPINLOCK_BUSY)
> + pm_runtime_put(&handle->pdev->dev);
> +
> + 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 */
> + writel(0, handle->lock_reg);
> +
> + pm_runtime_put(&handle->pdev->dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(hwspinlock_unlock);
> +
> +/* 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) {
> + 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_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;
> + struct resource *res;
> + void __iomem *io_base;
> + int id;
> +
> + void __iomem *sysstatus_reg;
> +
> + /* Determine number of locks */
> + sysstatus_reg = ioremap(OMAP44XX_SPINLOCK_BASE +
> +
> pdata->sysstatus_offset, sizeof(u32));
[sp] Is this the only place where sysstatus_reg is used? If so,
do we really need to pass it via pdata?
> + switch (readl(sysstatus_reg) >> SPINLOCK_NUMLOCKS_OFFSET) {
[sp] ioremap() is not guaranteed to succeed. Check if return value
is valid before using it.
> + case SPINLOCK_32_REGS:
> + hwspinlock_module->num_locks = 32;
> + break;
> + case SPINLOCK_64_REGS:
> + hwspinlock_module->num_locks = 64;
> + break;
> + case SPINLOCK_128_REGS:
> + hwspinlock_module->num_locks = 128;
> + break;
> + case SPINLOCK_256_REGS:
> + hwspinlock_module->num_locks = 256;
> + break;
> + default:
> + return -EINVAL; /* Invalid spinlock count code */
> + }
> + iounmap(sysstatus_reg);
> +
> + /* 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);
> +
> + /* Get address info */
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +
> + /* Map spinlock module address space */
> + io_base = ioremap(res->start, resource_size(res));
> + hwspinlock_module->io_base = io_base;
> +
> + /* Set up each individual lock handle */
> + for (id = 0; id < hwspinlock_module->num_locks; id++) {
> + hwspinlocks[id].id = id;
> + hwspinlocks[id].pdev = pdev;
> +
> + hwspinlocks[id].is_init = true;
> + hwspinlocks[id].is_allocated = false;
> +
> + hwspinlocks[id].lock_reg = io_base + pdata->
> + lock_base_offset +
> sizeof(u32) * id;
> + }
> +
> + 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);
> +
> + return retval;
> +}
> +
> +/* Cleanup function */
> +static void __exit hwspinlock_exit(void)
> +{
> + int id;
> +
> + platform_driver_unregister(&hwspinlock_driver);
> +
> + for (id = 0; id < hwspinlock_module->num_locks; id++)
> + hwspinlocks[id].is_init = false;
> + iounmap(hwspinlock_module->io_base);
> +
> + /* 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..8c69ca5
> --- /dev/null
> +++ b/arch/arm/plat-omap/include/plat/hwspinlock.h
> @@ -0,0 +1,29 @@
> +/* hwspinlock.h */
> +
> +#ifndef HWSPINLOCK_H
> +#define HWSPINLOCK_H
> +
[sp] License is missing
> +#include <linux/platform_device.h>
> +#include <plat/omap44xx.h>
> +
> +/* Read values from the spinlock register */
> +#define HWSPINLOCK_ACQUIRED 0
> +#define HWSPINLOCK_BUSY 1
[sp] What is the value after initialization?
Also, what is the difference between acquired and busy?
If a spinlock is acquired, won't it be busy? OR vice-versa?
> +
> +/* Device data */
> +struct hwspinlock_plat_info {
> + u32 sysstatus_offset; /* System status
> register offset */
> + u32 lock_base_offset; /* Offset of spinlock
> registers */
> +};
> +
> +struct hwspinlock;
[sp] Any specific reason for forward declaration?
> +
> +int hwspinlock_lock(struct hwspinlock *handle);
> +int hwspinlock_trylock(struct hwspinlock *handle);
> +int hwspinlock_unlock(struct hwspinlock *handle);
> +
> +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
>
> --
> To unsubscribe from this list: send the line "unsubscribe
> linux-omap" in
> the body of a message to majord...@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
