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Commit 6dc01aa6 authored by Chanho Min's avatar Chanho Min Committed by Greg Kroah-Hartman
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amba-pl011​/dma: Add check for the residue in DMA callback 



In DMA-operated uart, I found that rx data can be taken by the UART
interrupts during the DMA irq handler. pl011_int is occurred just
before it goes inside spin_lock_irq. When it returns to the callback,
DMA buffer already has been flushed. Then, pl011_dma_rx_chars gets
invalid data. So I add check for the residue as the patch bellow.

Signed-off-by: default avatarChanho Min <chanho.min@lge.com>
Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b26469a8

drivers/tty/serial/amba-pl011.c

+16 −1
Original line number Diff line number Diff line
@@ -827,7 +827,12 @@ static void pl011_dma_rx_callback(void *data) 
{

	struct uart_amba_port *uap = data;

	struct pl011_dmarx_data *dmarx = &uap->dmarx;

	struct dma_chan *rxchan = dmarx->chan;

	bool lastbuf = dmarx->use_buf_b;

	struct pl011_sgbuf *sgbuf = dmarx->use_buf_b ?

		&dmarx->sgbuf_b : &dmarx->sgbuf_a;

	size_t pending;

	struct dma_tx_state state;

	int ret;



	/*
@@ -838,11 +843,21 @@ static void pl011_dma_rx_callback(void *data) 
	 * we immediately trigger the next DMA job.

	 */

	spin_lock_irq(&uap->port.lock);

	/*

	 * Rx data can be taken by the UART interrupts during

	 * the DMA irq handler. So we check the residue here.

	 */

	rxchan->device->device_tx_status(rxchan, dmarx->cookie, &state);

	pending = sgbuf->sg.length - state.residue;

	BUG_ON(pending > PL011_DMA_BUFFER_SIZE);

	/* Then we terminate the transfer - we now know our residue */

	dmaengine_terminate_all(rxchan);



	uap->dmarx.running = false;

	dmarx->use_buf_b = !lastbuf;

	ret = pl011_dma_rx_trigger_dma(uap);



	pl011_dma_rx_chars(uap, PL011_DMA_BUFFER_SIZE, lastbuf, false);

	pl011_dma_rx_chars(uap, pending, lastbuf, false);

	spin_unlock_irq(&uap->port.lock);

	/*

	 * Do this check after we picked the DMA chars so we don't