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Commit 83167bef authored by Ryan Case's avatar Ryan Case Committed by Mukesh Kumar Savaliya
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tty: serial: qcom_geni_serial: Fix softlock 



Transfers were being divided into device FIFO sized (64 byte max)
operations which would poll for completion within a spin_lock_irqsave /
spin_unlock_irqrestore block. This both made things slow by waiting for
the FIFO to completely drain before adding further data and would also
result in softlocks on large transmissions.

This patch allows larger transfers with continuous FIFO additions as
space becomes available and removes polling from the interrupt handler.

Change-Id: I9225c86482550ca9f7433a585fdd0e4edf1b2f87
Signed-off-by: default avatarRyan Case <ryandcase@chromium.org>
Git-commit: a1fee899e5bed457afc20a6a2ff3915a95cc5942
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[msavaliy@codeaurora.org: Applied patch to downstream file - msm_geni_serial.c]
Signed-off-by: default avatarMukesh Kumar Savaliya <msavaliy@codeaurora.org>
parent eac6c82e

drivers/tty/serial/msm_geni_serial.c

+66 −20
Original line number Diff line number Diff line
@@ -170,6 +170,7 @@ struct msm_geni_serial_port { 
	int edge_count;

	bool manual_flow;

	struct msm_geni_serial_ver_info ver_info;

	u32 cur_tx_remaining;

};



static const struct uart_ops msm_geni_serial_pops;
@@ -771,8 +772,9 @@ static void msm_geni_serial_console_write(struct console *co, const char *s, 
{

	struct uart_port *uport;

	struct msm_geni_serial_port *port;

	int locked = 1;

	bool locked = true;

	unsigned long flags;

	unsigned int geni_status;



	WARN_ON(co->index < 0 || co->index >= GENI_UART_NR_PORTS);
@@ -786,11 +788,35 @@ static void msm_geni_serial_console_write(struct console *co, const char *s, 
	else

		spin_lock_irqsave(&uport->lock, flags);



	if (locked) {

	geni_status = readl_relaxed(uport->membase + SE_GENI_STATUS);



	/* Cancel the current write to log the fault */

	if (!locked) {

		geni_cancel_m_cmd(uport->membase);

		if (!msm_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS,

						M_CMD_CANCEL_EN, true)) {

			geni_abort_m_cmd(uport->membase);

			msm_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS,

							M_CMD_ABORT_EN, true);

			geni_write_reg_nolog(M_CMD_ABORT_EN, uport->membase,

							SE_GENI_M_IRQ_CLEAR);

		}

		writel_relaxed(M_CMD_CANCEL_EN, uport->membase +

							SE_GENI_M_IRQ_CLEAR);

	} else if ((geni_status & M_GENI_CMD_ACTIVE) && !port->cur_tx_remaining)

		/* It seems we can interrupt existing transfers unless all data

		 * has been sent, in which case we need to look for done first.

		 */

		msm_geni_serial_poll_cancel_tx(uport);



	__msm_geni_serial_console_write(uport, s, count);



	if (port->cur_tx_remaining)

		msm_geni_serial_setup_tx(uport, port->cur_tx_remaining);



	if (locked)

		spin_unlock_irqrestore(&uport->lock, flags);

}

}



static int handle_rx_console(struct uart_port *uport,

			unsigned int rx_fifo_wc,
@@ -1266,12 +1292,14 @@ static int msm_geni_serial_handle_rx(struct uart_port *uport, bool drop_rx) 
	return ret;

}



static int msm_geni_serial_handle_tx(struct uart_port *uport)

static int msm_geni_serial_handle_tx(struct uart_port *uport, bool done,

		bool active)

{

	struct msm_geni_serial_port *msm_port = GET_DEV_PORT(uport);

	struct circ_buf *xmit = &uport->state->xmit;

	unsigned int avail_fifo_bytes = 0;

	int avail_fifo_bytes = 0;

	unsigned int bytes_remaining = 0;

	unsigned int pending;

	int i = 0;

	unsigned int tx_fifo_status;

	unsigned int xmit_size;
@@ -1279,28 +1307,41 @@ static int msm_geni_serial_handle_tx(struct uart_port *uport) 
		(uart_console(uport) ? 1 : (msm_port->tx_fifo_width >> 3));

	int temp_tail = 0;



	xmit_size = uart_circ_chars_pending(xmit);

	tx_fifo_status = geni_read_reg_nolog(uport->membase,

					SE_GENI_TX_FIFO_STATUS);

	/* Both FIFO and framework buffer are drained */

	if (!xmit_size && !tx_fifo_status) {



	/* Complete the current tx command before taking newly added data */

	if (active)

		pending = msm_port->cur_tx_remaining;

	else

		pending = uart_circ_chars_pending(xmit);



	/* All data has been transmitted and acknowledged as received */

	if (!pending && !tx_fifo_status && done) {

		msm_geni_serial_stop_tx(uport);

		goto exit_handle_tx;

	}



	avail_fifo_bytes = (msm_port->tx_fifo_depth - msm_port->tx_wm) *

							fifo_width_bytes;

	temp_tail = xmit->tail & (UART_XMIT_SIZE - 1);

	avail_fifo_bytes = msm_port->tx_fifo_depth - (tx_fifo_status &

								TX_FIFO_WC);

	avail_fifo_bytes *= fifo_width_bytes;

	if (avail_fifo_bytes < 0)

		avail_fifo_bytes = 0;



	if (xmit_size > (UART_XMIT_SIZE - temp_tail))

		xmit_size = (UART_XMIT_SIZE - temp_tail);

	if (xmit_size > avail_fifo_bytes)

		xmit_size = avail_fifo_bytes;

	temp_tail = xmit->tail;

	xmit_size = min3((unsigned int)pending,

		(unsigned int)(UART_XMIT_SIZE - temp_tail),

		(unsigned int)avail_fifo_bytes);

	if (!xmit_size)

		goto exit_handle_tx;



	msm_geni_serial_setup_tx(uport, xmit_size);

	if (!msm_port->cur_tx_remaining) {

		msm_geni_serial_setup_tx(uport, pending);

		msm_port->cur_tx_remaining = pending;

	}



	bytes_remaining = xmit_size;



	while (i < xmit_size) {

		unsigned int tx_bytes;

		unsigned int buf = 0;
@@ -1311,17 +1352,18 @@ static int msm_geni_serial_handle_tx(struct uart_port *uport) 


		for (c = 0; c < tx_bytes ; c++)

			buf |= (xmit->buf[temp_tail + c] << (c * 8));



		geni_write_reg_nolog(buf, uport->membase, SE_GENI_TX_FIFOn);



		i += tx_bytes;

		bytes_remaining -= tx_bytes;

		uport->icount.tx += tx_bytes;

		temp_tail += tx_bytes;

		msm_port->cur_tx_remaining -= tx_bytes;

		/* Ensure FIFO write goes through */

		wmb();

	}

	xmit->tail = temp_tail & (UART_XMIT_SIZE - 1);

	if (uart_console(uport))

		msm_geni_serial_poll_cancel_tx(uport);

exit_handle_tx:

	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)

		uart_write_wakeup(uport);
@@ -1418,6 +1460,7 @@ static irqreturn_t msm_geni_serial_isr(int isr, void *dev) 
	struct uart_port *uport = dev;

	unsigned long flags;

	unsigned int m_irq_en;

	unsigned int geni_status;

	struct msm_geni_serial_port *msm_port = GET_DEV_PORT(uport);

	struct tty_port *tport = &uport->state->port;

	bool drop_rx = false;
@@ -1439,6 +1482,7 @@ static irqreturn_t msm_geni_serial_isr(int isr, void *dev) 
	dma = geni_read_reg_nolog(uport->membase, SE_GENI_DMA_MODE_EN);

	dma_tx_status = geni_read_reg_nolog(uport->membase, SE_DMA_TX_IRQ_STAT);

	dma_rx_status = geni_read_reg_nolog(uport->membase, SE_DMA_RX_IRQ_STAT);

	geni_status = readl_relaxed(uport->membase + SE_GENI_STATUS);



	geni_write_reg_nolog(m_irq_status, uport->membase, SE_GENI_M_IRQ_CLEAR);

	geni_write_reg_nolog(s_irq_status, uport->membase, SE_GENI_S_IRQ_CLEAR);
@@ -1459,7 +1503,9 @@ static irqreturn_t msm_geni_serial_isr(int isr, void *dev) 
	if (!dma) {

		if ((m_irq_status & m_irq_en) &

		    (M_TX_FIFO_WATERMARK_EN | M_CMD_DONE_EN))

			msm_geni_serial_handle_tx(uport);

			msm_geni_serial_handle_tx(uport,

					m_irq_status & M_CMD_DONE_EN,

					geni_status & M_GENI_CMD_ACTIVE);



		if ((s_irq_status & S_GP_IRQ_0_EN) ||

			(s_irq_status & S_GP_IRQ_1_EN)) {