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spi: spidev: Use separate TX and RX bounce buffers
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By using separate TX and RX bounce buffers, we avoid potential cache
flush and invalidation sequence issue that may be encountered when a
single bounce buffer is shared between TX and RX

Signed-off-by: Ray Jui <rjui@broadcom.com>
Reviewed-by: JD (Jiandong) Zheng <jdzheng@broadcom.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
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Ray Jui authored and Mark Brown committed Oct 13, 2014
1 parent a2285b8 commit 865f6d1
Showing 1 changed file with 52 additions and 27 deletions.
79 changes: 52 additions & 27 deletions drivers/spi/spidev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -82,10 +82,11 @@ struct spidev_data {
struct spi_device *spi;
struct list_head device_entry;

/* buffer is NULL unless this device is open (users > 0) */
/* TX/RX buffers are NULL unless this device is open (users > 0) */
struct mutex buf_lock;
unsigned users;
u8 *buffer;
u8 *tx_buffer;
u8 *rx_buffer;
};

static LIST_HEAD(device_list);
Expand Down Expand Up @@ -135,7 +136,7 @@ static inline ssize_t
spidev_sync_write(struct spidev_data *spidev, size_t len)
{
struct spi_transfer t = {
.tx_buf = spidev->buffer,
.tx_buf = spidev->tx_buffer,
.len = len,
};
struct spi_message m;
Expand All @@ -149,7 +150,7 @@ static inline ssize_t
spidev_sync_read(struct spidev_data *spidev, size_t len)
{
struct spi_transfer t = {
.rx_buf = spidev->buffer,
.rx_buf = spidev->rx_buffer,
.len = len,
};
struct spi_message m;
Expand Down Expand Up @@ -179,7 +180,7 @@ spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
if (status > 0) {
unsigned long missing;

missing = copy_to_user(buf, spidev->buffer, status);
missing = copy_to_user(buf, spidev->rx_buffer, status);
if (missing == status)
status = -EFAULT;
else
Expand All @@ -206,7 +207,7 @@ spidev_write(struct file *filp, const char __user *buf,
spidev = filp->private_data;

mutex_lock(&spidev->buf_lock);
missing = copy_from_user(spidev->buffer, buf, count);
missing = copy_from_user(spidev->tx_buffer, buf, count);
if (missing == 0)
status = spidev_sync_write(spidev, count);
else
Expand All @@ -224,7 +225,7 @@ static int spidev_message(struct spidev_data *spidev,
struct spi_transfer *k_tmp;
struct spi_ioc_transfer *u_tmp;
unsigned n, total;
u8 *buf;
u8 *tx_buf, *rx_buf;
int status = -EFAULT;

spi_message_init(&msg);
Expand All @@ -236,7 +237,8 @@ static int spidev_message(struct spidev_data *spidev,
* We walk the array of user-provided transfers, using each one
* to initialize a kernel version of the same transfer.
*/
buf = spidev->buffer;
tx_buf = spidev->tx_buffer;
rx_buf = spidev->rx_buffer;
total = 0;
for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
n;
Expand All @@ -250,20 +252,21 @@ static int spidev_message(struct spidev_data *spidev,
}

if (u_tmp->rx_buf) {
k_tmp->rx_buf = buf;
k_tmp->rx_buf = rx_buf;
if (!access_ok(VERIFY_WRITE, (u8 __user *)
(uintptr_t) u_tmp->rx_buf,
u_tmp->len))
goto done;
}
if (u_tmp->tx_buf) {
k_tmp->tx_buf = buf;
if (copy_from_user(buf, (const u8 __user *)
k_tmp->tx_buf = tx_buf;
if (copy_from_user(tx_buf, (const u8 __user *)
(uintptr_t) u_tmp->tx_buf,
u_tmp->len))
goto done;
}
buf += k_tmp->len;
tx_buf += k_tmp->len;
rx_buf += k_tmp->len;

k_tmp->cs_change = !!u_tmp->cs_change;
k_tmp->tx_nbits = u_tmp->tx_nbits;
Expand All @@ -290,17 +293,17 @@ static int spidev_message(struct spidev_data *spidev,
goto done;

/* copy any rx data out of bounce buffer */
buf = spidev->buffer;
rx_buf = spidev->rx_buffer;
for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
if (u_tmp->rx_buf) {
if (__copy_to_user((u8 __user *)
(uintptr_t) u_tmp->rx_buf, buf,
(uintptr_t) u_tmp->rx_buf, rx_buf,
u_tmp->len)) {
status = -EFAULT;
goto done;
}
}
buf += u_tmp->len;
rx_buf += u_tmp->len;
}
status = total;

Expand Down Expand Up @@ -508,22 +511,41 @@ static int spidev_open(struct inode *inode, struct file *filp)
break;
}
}
if (status == 0) {
if (!spidev->buffer) {
spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
if (!spidev->buffer) {

if (status) {
pr_debug("spidev: nothing for minor %d\n", iminor(inode));
goto err_find_dev;
}

if (!spidev->tx_buffer) {
spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
if (!spidev->tx_buffer) {
dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
status = -ENOMEM;
goto err_find_dev;
}
}
if (status == 0) {
spidev->users++;
filp->private_data = spidev;
nonseekable_open(inode, filp);

if (!spidev->rx_buffer) {
spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
if (!spidev->rx_buffer) {
dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
status = -ENOMEM;
goto err_alloc_rx_buf;
}
} else
pr_debug("spidev: nothing for minor %d\n", iminor(inode));
}

spidev->users++;
filp->private_data = spidev;
nonseekable_open(inode, filp);

mutex_unlock(&device_list_lock);
return 0;

err_alloc_rx_buf:
kfree(spidev->tx_buffer);
spidev->tx_buffer = NULL;
err_find_dev:
mutex_unlock(&device_list_lock);
return status;
}
Expand All @@ -542,8 +564,11 @@ static int spidev_release(struct inode *inode, struct file *filp)
if (!spidev->users) {
int dofree;

kfree(spidev->buffer);
spidev->buffer = NULL;
kfree(spidev->tx_buffer);
spidev->tx_buffer = NULL;

kfree(spidev->rx_buffer);
spidev->rx_buffer = NULL;

/* ... after we unbound from the underlying device? */
spin_lock_irq(&spidev->spi_lock);
Expand Down

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