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/*
* arch/arm/mach-tegra/sysfs-dcc.c
*
* Copyright (c) 2010-2013, NVIDIA CORPORATION, All rights reserved.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/sysfs.h>
#include <linux/workqueue.h>
#include <linux/kobject.h>
#include <linux/hrtimer.h>
#include <linux/slab.h>
#define DCC_TIMEOUT_US 100000 /* Delay time for DCC timeout (in uS) */
#define CP14_DSCR_WDTRFULL 0x20000000 /* Write Data Transfer Register Full */
#define SYSFS_DCC_DEBUG_PRINTS 0 /* Set non-zero to enable debug prints */
#if SYSFS_DCC_DEBUG_PRINTS
#define DEBUG_DCC(x) printk x
#else
#define DEBUG_DCC(x)
#endif
static int DebuggerConnected = 0; /* -1=not connected, 0=unknown, 1=connected */
static struct kobject *nvdcc_kobj;
static spinlock_t dcc_lock;
static struct list_head dcc_list;
static ssize_t sysfsdcc_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf);
static ssize_t sysfsdcc_store(struct kobject *kobj,
struct kobj_attribute *attr, const char *buf, size_t count);
static struct kobj_attribute nvdcc_attr =
__ATTR(dcc0, 0222, sysfsdcc_show, sysfsdcc_store);
static int write_to_dcc(u32 c)
{
volatile u32 dscr;
/* Have we already determined that there is no debugger connected? */
if (DebuggerConnected < 0)
{
return -ENXIO;
}
/* Read the DSCR. */
asm volatile ("mrc p14, 0, %0, c0, c1, 0" : "=r" (dscr) : : "cc");
/* If DSCR Bit 29 (wDTRFull) is set there is data in the write
* register. If it stays there for than the DCC_TIMEOUT_US
* period, ignore this write and disable further DCC accesses. */
if (dscr & CP14_DSCR_WDTRFULL)
{
ktime_t end = ktime_add_ns(ktime_get(), DCC_TIMEOUT_US * 1000);
ktime_t now;
for (;;)
{
/* Re-read the DSCR. */
asm volatile ("mrc p14, 0, %0, c0, c1, 0" : "=r" (dscr) : : "cc");
/* Previous data still there? */
if (dscr & CP14_DSCR_WDTRFULL)
{
now = ktime_get();
if (ktime_to_ns(now) >= ktime_to_ns(end))
{
goto fail;
}
}
else
{
if (DebuggerConnected == 0) {
/* Debugger connected */
spin_lock(&dcc_lock);
DebuggerConnected = 1;
spin_unlock(&dcc_lock);
}
break;
}
}
}
// Write the data into the DCC output register
asm volatile ("mcr p14, 0, %0, c0, c5, 0" : : "r" (c) : "cc");
return 0;
fail:
/* No debugged connected -- disable DCC */
spin_lock(&dcc_lock);
DebuggerConnected = -1;
spin_unlock(&dcc_lock);
return -ENXIO;
}
struct tegra_dcc_req {
struct list_head node;
const char *pBuf;
unsigned int size;
};
struct dcc_action {
struct tegra_dcc_req req;
struct work_struct work;
struct list_head node;
};
static void dcc_writer(struct work_struct *work)
{
struct dcc_action *action = container_of(work, struct dcc_action, work);
const char *p;
DEBUG_DCC(("+dcc_writer\n"));
spin_lock(&dcc_lock);
list_del(&action->req.node);
spin_unlock(&dcc_lock);
p = action->req.pBuf;
if (p)
while ((p < &(action->req.pBuf[action->req.size])) && (*p))
if (write_to_dcc(*p++))
break;
kfree(action->req.pBuf);
kfree(action);
DEBUG_DCC(("-dcc_writer\n"));
}
static ssize_t sysfsdcc_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
DEBUG_DCC(("!sysfsdcc_show\n"));
return -EACCES;
}
static ssize_t sysfsdcc_store(struct kobject *kobj,
struct kobj_attribute *attr, const char *buf, size_t count)
{
struct dcc_action *action;
char *pBuf;
ssize_t ret = count;
DEBUG_DCC(("+sysfsdcc_store: %p, %d\n", buf, count));
if (!buf || !count) {
ret = -EINVAL;
goto fail;
}
pBuf = kmalloc(count+1, GFP_KERNEL);
if (!pBuf) {
pr_debug("%s: insufficient memory\n", __func__);
ret = -ENOMEM;
goto fail;
}
action = kzalloc(sizeof(*action), GFP_KERNEL);
if (!action) {
kfree(pBuf);
pr_debug("%s: insufficient memory\n", __func__);
ret = -ENOMEM;
goto fail;
}
strncpy(pBuf, buf, count);
pBuf[count] = '\0';
action->req.pBuf = pBuf;
action->req.size = count;
INIT_WORK(&action->work, dcc_writer);
spin_lock(&dcc_lock);
list_add_tail(&action->req.node, &dcc_list);
spin_unlock(&dcc_lock);
/* DCC writes can only be performed from CPU0 */
schedule_work_on(0, &action->work);
fail:
DEBUG_DCC(("-sysfsdcc_store: %d\n", count));
return ret;
}
static int __init sysfsdcc_init(void)
{
spin_lock_init(&dcc_lock);
INIT_LIST_HEAD(&dcc_list);
DEBUG_DCC(("+sysfsdcc_init\n"));
nvdcc_kobj = kobject_create_and_add("dcc", kernel_kobj);
if (sysfs_create_file(nvdcc_kobj, &nvdcc_attr.attr))
{
DEBUG_DCC(("DCC: sysfs_create_file failed!\n"));
return -ENXIO;
}
DEBUG_DCC(("-sysfsdcc_init\n"));
return 0;
}
static void __exit sysfsdcc_exit(void)
{
DEBUG_DCC(("+sysfsdcc_exit\n"));
sysfs_remove_file(nvdcc_kobj, &nvdcc_attr.attr);
kobject_del(nvdcc_kobj);
DEBUG_DCC(("-sysfsdcc_exit\n"));
}
module_init(sysfsdcc_init);
module_exit(sysfsdcc_exit);
MODULE_LICENSE("GPL");
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