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tty: serial: 8250: omap: synchronize rx_running 

The rx_running flag should show if DMA is currently active. However
there is a window between when the flag is set/cleared and when
the DMA is started/stopped. Because the flag is queried from both
hard and soft irq contexts, the driver can make incorrect
decisions and do things like start a DMA transfer using a buffer
that is already setup to be used for a DMA transfer.

This patch adds a spinlock to synchronize the rx_running flag and
close the above mentioned window.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
John Ogness 2015-04-27 13:52:33 +02:00 committed by Greg Kroah-Hartman
parent 02ec6041a8
commit eda0cd3546
1 changed files with 49 additions and 16 deletions
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65
drivers/tty/serial/8250/8250_omap.c
View File

@ -98,6 +98,7 @@ struct omap8250_priv {
struct pm_qos_request pm_qos_request;
struct work_struct qos_work;
struct uart_8250_dma omap8250_dma;
spinlock_t rx_dma_lock;
};
static u32 uart_read(struct uart_8250_port *up, u32 reg)
@ -669,14 +670,21 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir);
static void __dma_rx_do_complete(struct uart_8250_port *p, bool error)
{
struct omap8250_priv *priv = p->port.private_data;
struct uart_8250_dma *dma = p->dma;
struct tty_port *tty_port = &p->port.state->port;
struct dma_tx_state state;
int count;
unsigned long flags;
dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
dma->rx_size, DMA_FROM_DEVICE);
spin_lock_irqsave(&priv->rx_dma_lock, flags);
if (!dma->rx_running)
goto unlock;
dma->rx_running = 0;
dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
dmaengine_terminate_all(dma->rxchan);
@ -685,6 +693,9 @@ static void __dma_rx_do_complete(struct uart_8250_port *p, bool error)
tty_insert_flip_string(tty_port, dma->rx_buf, count);
p->port.icount.rx += count;
unlock:
spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
if (!error)
omap_8250_rx_dma(p, 0);
@ -696,28 +707,45 @@ static void __dma_rx_complete(void *param)
__dma_rx_do_complete(param, false);
}
static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
{
struct omap8250_priv *priv = p->port.private_data;
struct uart_8250_dma *dma = p->dma;
unsigned long flags;
spin_lock_irqsave(&priv->rx_dma_lock, flags);
if (!dma->rx_running) {
spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
return;
}
dmaengine_pause(dma->rxchan);
spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
__dma_rx_do_complete(p, true);
}
static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
{
struct omap8250_priv *priv = p->port.private_data;
struct uart_8250_dma *dma = p->dma;
int err = 0;
struct dma_async_tx_descriptor *desc;
unsigned long flags;
switch (iir & 0x3f) {
case UART_IIR_RLSI:
/* 8250_core handles errors and break interrupts */
if (dma->rx_running) {
dmaengine_pause(dma->rxchan);
__dma_rx_do_complete(p, true);
}
omap_8250_rx_dma_flush(p);
return -EIO;
case UART_IIR_RX_TIMEOUT:
/*
* If RCVR FIFO trigger level was not reached, complete the
* transfer and let 8250_core copy the remaining data.
*/
if (dma->rx_running) {
dmaengine_pause(dma->rxchan);
__dma_rx_do_complete(p, true);
}
omap_8250_rx_dma_flush(p);
return -ETIMEDOUT;
case UART_IIR_RDI:
/*
@ -729,24 +757,25 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
* the DMA won't do anything soon so we have to cancel the DMA
* transfer and purge the FIFO manually.
*/
if (dma->rx_running) {
dmaengine_pause(dma->rxchan);
__dma_rx_do_complete(p, true);
}
omap_8250_rx_dma_flush(p);
return -ETIMEDOUT;
default:
break;
}
spin_lock_irqsave(&priv->rx_dma_lock, flags);
if (dma->rx_running)
return 0;
goto out;
desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
dma->rx_size, DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EBUSY;
if (!desc) {
err = -EBUSY;
goto out;
}
dma->rx_running = 1;
desc->callback = __dma_rx_complete;
@ -758,7 +787,9 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
dma->rx_size, DMA_FROM_DEVICE);
dma_async_issue_pending(dma->rxchan);
return 0;
out:
spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
return err;
}
static int omap_8250_tx_dma(struct uart_8250_port *p);
@ -1065,6 +1096,8 @@ static int omap8250_probe(struct platform_device *pdev)
priv->latency);
INIT_WORK(&priv->qos_work, omap8250_uart_qos_work);
spin_lock_init(&priv->rx_dma_lock);
device_init_wakeup(&pdev->dev, true);
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_set_autosuspend_delay(&pdev->dev, -1);