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drivers/misc: Aspeed LPC snoop output using misc chardev

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Provides the data bytes snooped over the LPC snoop bus to userspace
as a (blocking) misc character device.

Bytes output from the host using LPC I/O transactions to the snooped port
can be watched or retrieved from the character device using a simple
command like this:
~#  od -w1 -A n -t x1 /dev/aspeed-lpc-snoop0
 10
 de
 ad
 c0
 ff
 ee

Signed-off-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Benjamin Fair <benjaminfair@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Robert Lippert 2018-07-06 11:25:32 -07:00 committed by Greg Kroah-Hartman
parent 7f3838fb8c
commit 3772e5da44
1 changed files with 74 additions and 10 deletions
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84
drivers/misc/aspeed-lpc-snoop.c
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@ -16,12 +16,15 @@
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/kfifo.h>
#include <linux/mfd/syscon.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
#include <linux/regmap.h>
#define DEVICE_NAME "aspeed-lpc-snoop"
@ -59,20 +62,70 @@ struct aspeed_lpc_snoop_model_data {
unsigned int has_hicrb_ensnp;
};
struct aspeed_lpc_snoop_channel {
struct kfifo fifo;
wait_queue_head_t wq;
struct miscdevice miscdev;
};
struct aspeed_lpc_snoop {
struct regmap *regmap;
int irq;
struct kfifo snoop_fifo[NUM_SNOOP_CHANNELS];
struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
};
static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
{
return container_of(file->private_data,
struct aspeed_lpc_snoop_channel,
miscdev);
}
static ssize_t snoop_file_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
unsigned int copied;
int ret = 0;
if (kfifo_is_empty(&chan->fifo)) {
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
ret = wait_event_interruptible(chan->wq,
!kfifo_is_empty(&chan->fifo));
if (ret == -ERESTARTSYS)
return -EINTR;
}
ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
return ret ? ret : copied;
}
static unsigned int snoop_file_poll(struct file *file,
struct poll_table_struct *pt)
{
struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
poll_wait(file, &chan->wq, pt);
return !kfifo_is_empty(&chan->fifo) ? POLLIN : 0;
}
static const struct file_operations snoop_fops = {
.owner = THIS_MODULE,
.read = snoop_file_read,
.poll = snoop_file_poll,
.llseek = noop_llseek,
};
/* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
static void put_fifo_with_discard(struct kfifo *fifo, u8 val)
static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
{
if (!kfifo_initialized(fifo))
if (!kfifo_initialized(&chan->fifo))
return;
if (kfifo_is_full(fifo))
kfifo_skip(fifo);
kfifo_put(fifo, val);
if (kfifo_is_full(&chan->fifo))
kfifo_skip(&chan->fifo);
kfifo_put(&chan->fifo, val);
wake_up_interruptible(&chan->wq);
}
static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
@ -97,12 +150,12 @@ static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
if (reg & HICR6_STR_SNP0W) {
u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
put_fifo_with_discard(&lpc_snoop->snoop_fifo[0], val);
put_fifo_with_discard(&lpc_snoop->chan[0], val);
}
if (reg & HICR6_STR_SNP1W) {
u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
put_fifo_with_discard(&lpc_snoop->snoop_fifo[1], val);
put_fifo_with_discard(&lpc_snoop->chan[1], val);
}
return IRQ_HANDLED;
@ -139,12 +192,22 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
const struct aspeed_lpc_snoop_model_data *model_data =
of_device_get_match_data(dev);
init_waitqueue_head(&lpc_snoop->chan[channel].wq);
/* Create FIFO datastructure */
rc = kfifo_alloc(&lpc_snoop->snoop_fifo[channel],
rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
SNOOP_FIFO_SIZE, GFP_KERNEL);
if (rc)
return rc;
lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
lpc_snoop->chan[channel].miscdev.name =
devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
lpc_snoop->chan[channel].miscdev.parent = dev;
rc = misc_register(&lpc_snoop->chan[channel].miscdev);
if (rc)
return rc;
/* Enable LPC snoop channel at requested port */
switch (channel) {
case 0:
@ -191,7 +254,8 @@ static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
return;
}
kfifo_free(&lpc_snoop->snoop_fifo[channel]);
kfifo_free(&lpc_snoop->chan[channel].fifo);
misc_deregister(&lpc_snoop->chan[channel].miscdev);
}
static int aspeed_lpc_snoop_probe(struct platform_device *pdev)