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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:
parent
02ec6041a8
commit
eda0cd3546
1 changed files with 49 additions and 16 deletions
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@ -98,6 +98,7 @@ struct omap8250_priv {
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struct pm_qos_request pm_qos_request;
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struct work_struct qos_work;
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struct uart_8250_dma omap8250_dma;
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spinlock_t rx_dma_lock;
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};
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static u32 uart_read(struct uart_8250_port *up, u32 reg)
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@ -669,14 +670,21 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir);
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static void __dma_rx_do_complete(struct uart_8250_port *p, bool error)
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{
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struct omap8250_priv *priv = p->port.private_data;
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struct uart_8250_dma *dma = p->dma;
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struct tty_port *tty_port = &p->port.state->port;
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struct dma_tx_state state;
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int count;
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unsigned long flags;
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dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
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dma->rx_size, DMA_FROM_DEVICE);
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spin_lock_irqsave(&priv->rx_dma_lock, flags);
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if (!dma->rx_running)
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goto unlock;
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dma->rx_running = 0;
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dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
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dmaengine_terminate_all(dma->rxchan);
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@ -685,6 +693,9 @@ static void __dma_rx_do_complete(struct uart_8250_port *p, bool error)
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tty_insert_flip_string(tty_port, dma->rx_buf, count);
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p->port.icount.rx += count;
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unlock:
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spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
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if (!error)
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omap_8250_rx_dma(p, 0);
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@ -696,28 +707,45 @@ static void __dma_rx_complete(void *param)
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__dma_rx_do_complete(param, false);
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}
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static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
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{
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struct omap8250_priv *priv = p->port.private_data;
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struct uart_8250_dma *dma = p->dma;
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unsigned long flags;
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spin_lock_irqsave(&priv->rx_dma_lock, flags);
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if (!dma->rx_running) {
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spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
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return;
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}
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dmaengine_pause(dma->rxchan);
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spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
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__dma_rx_do_complete(p, true);
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}
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static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
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{
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struct omap8250_priv *priv = p->port.private_data;
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struct uart_8250_dma *dma = p->dma;
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int err = 0;
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struct dma_async_tx_descriptor *desc;
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unsigned long flags;
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switch (iir & 0x3f) {
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case UART_IIR_RLSI:
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/* 8250_core handles errors and break interrupts */
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if (dma->rx_running) {
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dmaengine_pause(dma->rxchan);
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__dma_rx_do_complete(p, true);
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}
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omap_8250_rx_dma_flush(p);
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return -EIO;
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case UART_IIR_RX_TIMEOUT:
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/*
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* If RCVR FIFO trigger level was not reached, complete the
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* transfer and let 8250_core copy the remaining data.
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*/
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if (dma->rx_running) {
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dmaengine_pause(dma->rxchan);
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__dma_rx_do_complete(p, true);
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}
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omap_8250_rx_dma_flush(p);
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return -ETIMEDOUT;
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case UART_IIR_RDI:
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/*
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@ -729,24 +757,25 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
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* the DMA won't do anything soon so we have to cancel the DMA
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* transfer and purge the FIFO manually.
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*/
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if (dma->rx_running) {
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dmaengine_pause(dma->rxchan);
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__dma_rx_do_complete(p, true);
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}
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omap_8250_rx_dma_flush(p);
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return -ETIMEDOUT;
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default:
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break;
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}
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spin_lock_irqsave(&priv->rx_dma_lock, flags);
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if (dma->rx_running)
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return 0;
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goto out;
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desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
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dma->rx_size, DMA_DEV_TO_MEM,
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DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
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if (!desc)
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return -EBUSY;
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if (!desc) {
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err = -EBUSY;
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goto out;
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}
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dma->rx_running = 1;
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desc->callback = __dma_rx_complete;
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@ -758,7 +787,9 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
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dma->rx_size, DMA_FROM_DEVICE);
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dma_async_issue_pending(dma->rxchan);
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return 0;
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out:
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spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
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return err;
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}
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static int omap_8250_tx_dma(struct uart_8250_port *p);
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@ -1065,6 +1096,8 @@ static int omap8250_probe(struct platform_device *pdev)
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priv->latency);
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INIT_WORK(&priv->qos_work, omap8250_uart_qos_work);
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spin_lock_init(&priv->rx_dma_lock);
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device_init_wakeup(&pdev->dev, true);
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pm_runtime_use_autosuspend(&pdev->dev);
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pm_runtime_set_autosuspend_delay(&pdev->dev, -1);
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