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Date: Mon, 17 Aug 2015 16:00:20 +0000
From: Anirudha Sarangi <anirudha.sarangi@...inx.com>
To: Peter Hurley <peter@...leysoftware.com>,
Michal Simek <michals@...inx.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"monstr@...str.eu" <monstr@...str.eu>,
Soren Brinkmann <sorenb@...inx.com>,
Jiri Slaby <jslaby@...e.com>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 4/4] serial: xuartps: Rewrite the interrupt handling
logic
Hi,
> -----Original Message-----
> From: Peter Hurley [mailto:peter@...leysoftware.com]
> Sent: Monday, August 17, 2015 9:26 PM
> To: Michal Simek
> Cc: linux-kernel@...r.kernel.org; monstr@...str.eu; Anirudha Sarangi; Soren
> Brinkmann; Jiri Slaby; linux-serial@...r.kernel.org; Greg Kroah-Hartman; linux-
> arm-kernel@...ts.infradead.org
> Subject: Re: [PATCH 4/4] serial: xuartps: Rewrite the interrupt handling logic
>
> On 08/17/2015 03:22 AM, Michal Simek wrote:
> > From: Anirudha Sarangi <anirudha.sarangi@...inx.com>
> >
> > The existing interrupt handling logic has followins issues.
> > - Upon a parity error with default configuration, the control
> > never comes out of the ISR thereby hanging Linux.
> > - The error handling logic around framing and parity error are buggy.
> > There are chances that the errors will never be captured.
> > - The existing ISR is just too long.
> > This patch fixes all these concerns.
>
> This patch is unreviewable. Please break this down into multiple patches.
>
Thanks. Let me give a shot. It is just breaking the single big ISR that has both Rx and Tx in a single function into smaller ones.
Not sure how I will create smaller patches, but I will try and get back.
Regards
Anirudha
> Regards,
> Peter Hurley
>
> > It separates out the Tx and Rx
> > hanling logic into separate functions. It ensures that the status
> > registers are cleared on all cases so that a hang situation never
> > arises.
> >
> > Signed-off-by: Anirudha Sarangi <anirudh@...inx.com>
> > Signed-off-by: Michal Simek <michal.simek@...inx.com>
> > ---
> >
> > drivers/tty/serial/xilinx_uartps.c | 194
> > ++++++++++++++++++++-----------------
> > 1 file changed, 104 insertions(+), 90 deletions(-)
> >
> > diff --git a/drivers/tty/serial/xilinx_uartps.c
> > b/drivers/tty/serial/xilinx_uartps.c
> > index 2dc26e5f1384..c771dbbf6161 100644
> > --- a/drivers/tty/serial/xilinx_uartps.c
> > +++ b/drivers/tty/serial/xilinx_uartps.c
> > @@ -173,61 +173,86 @@ struct cdns_uart {
> > clk_rate_change_nb);
> >
> > /**
> > - * cdns_uart_isr - Interrupt handler
> > - * @irq: Irq number
> > - * @dev_id: Id of the port
> > - *
> > - * Return: IRQHANDLED
> > + * cdns_uart_handle_tx - Handle the bytes to be Txed.
> > + * @dev_id: Id of the UART port
> > + * Return: None
> > */
> > -static irqreturn_t cdns_uart_isr(int irq, void *dev_id)
> > +static void cdns_uart_handle_tx(void *dev_id)
> > {
> > struct uart_port *port = (struct uart_port *)dev_id;
> > - unsigned long flags;
> > - unsigned int isrstatus, numbytes;
> > - unsigned int data;
> > - char status = TTY_NORMAL;
> > + unsigned int numbytes;
> >
> > - spin_lock_irqsave(&port->lock, flags);
> > + if (uart_circ_empty(&port->state->xmit)) {
> > + writel(CDNS_UART_IXR_TXEMPTY, port->membase +
> > + CDNS_UART_IDR_OFFSET);
> > + } else {
> > + numbytes = port->fifosize;
> > + /* Break if no more data available in the UART buffer */
> > + while (numbytes--) {
> > + if (uart_circ_empty(&port->state->xmit))
> > + break;
> > + /*
> > + * Get the data from the UART circular buffer
> > + * and write it to the cdns_uart's TX_FIFO
> > + * register.
> > + */
> > + writel(port->state->xmit.buf[port->state->xmit.tail],
> > + port->membase + CDNS_UART_FIFO_OFFSET);
> >
> > - /* Read the interrupt status register to determine which
> > - * interrupt(s) is/are active.
> > - */
> > - isrstatus = readl(port->membase + CDNS_UART_ISR_OFFSET);
> > + port->icount.tx++;
> >
> > - /*
> > - * There is no hardware break detection, so we interpret framing
> > - * error with all-zeros data as a break sequence. Most of the time,
> > - * there's another non-zero byte at the end of the sequence.
> > - */
> > - if (isrstatus & CDNS_UART_IXR_FRAMING) {
> > - while (!(readl(port->membase + CDNS_UART_SR_OFFSET) &
> > - CDNS_UART_SR_RXEMPTY)) {
> > - if (!readl(port->membase + CDNS_UART_FIFO_OFFSET))
> {
> > - port->read_status_mask |=
> CDNS_UART_IXR_BRK;
> > - isrstatus &= ~CDNS_UART_IXR_FRAMING;
> > - }
> > + /*
> > + * Adjust the tail of the UART buffer and wrap
> > + * the buffer if it reaches limit.
> > + */
> > + port->state->xmit.tail =
> > + (port->state->xmit.tail + 1) &
> > + (UART_XMIT_SIZE - 1);
> > }
> > - writel(CDNS_UART_IXR_FRAMING,
> > - port->membase + CDNS_UART_ISR_OFFSET);
> > - }
> >
> > - /* drop byte with parity error if IGNPAR specified */
> > - if (isrstatus & port->ignore_status_mask & CDNS_UART_IXR_PARITY)
> > - isrstatus &= ~(CDNS_UART_IXR_RXTRIG |
> CDNS_UART_IXR_TOUT);
> > + if (uart_circ_chars_pending(
> > + &port->state->xmit) < WAKEUP_CHARS)
> > + uart_write_wakeup(port);
> > + }
> > +}
> >
> > - isrstatus &= port->read_status_mask;
> > - isrstatus &= ~port->ignore_status_mask;
> > +/**
> > + * cdns_uart_handle_rx - Handle the received bytes along with Rx errors.
> > + * @dev_id: Id of the UART port
> > + * @isrstatus: The interrupt status register value as read
> > + * Return: None
> > + */
> > +static void cdns_uart_handle_rx(void *dev_id, unsigned int isrstatus)
> > +{
> > + struct uart_port *port = (struct uart_port *)dev_id;
> > + unsigned int data;
> > + unsigned int framerrprocessed = 0;
> > + char status = TTY_NORMAL;
> >
> > - if ((isrstatus & CDNS_UART_IXR_TOUT) ||
> > - (isrstatus & CDNS_UART_IXR_RXTRIG)) {
> > - /* Receive Timeout Interrupt */
> > - while (!(readl(port->membase + CDNS_UART_SR_OFFSET) &
> > - CDNS_UART_SR_RXEMPTY)) {
> > - data = readl(port->membase +
> CDNS_UART_FIFO_OFFSET);
> > + while ((readl(port->membase + CDNS_UART_SR_OFFSET) &
> > + CDNS_UART_SR_RXEMPTY) != CDNS_UART_SR_RXEMPTY) {
> > + data = readl(port->membase + CDNS_UART_FIFO_OFFSET);
> > + port->icount.rx++;
> > + /*
> > + * There is no hardware break detection, so we interpret
> > + * framing error with all-zeros data as a break sequence.
> > + * Most of the time, there's another non-zero byte at the
> > + * end of the sequence.
> > + */
> > + if (isrstatus & CDNS_UART_IXR_FRAMING) {
> > + if (!data) {
> > + port->read_status_mask |=
> CDNS_UART_IXR_BRK;
> > + framerrprocessed = 1;
> > + continue;
> > + }
> > + }
> > + isrstatus &= port->read_status_mask;
> > + isrstatus &= ~port->ignore_status_mask;
> >
> > - /* Non-NULL byte after BREAK is garbage (99%) */
> > - if (data && (port->read_status_mask &
> > - CDNS_UART_IXR_BRK)) {
> > + if ((isrstatus & CDNS_UART_IXR_TOUT) ||
> > + (isrstatus & CDNS_UART_IXR_RXTRIG)) {
> > + if (data &&
> > + (port->read_status_mask & CDNS_UART_IXR_BRK)) {
> > port->read_status_mask &=
> ~CDNS_UART_IXR_BRK;
> > port->icount.brk++;
> > if (uart_handle_break(port))
> > @@ -249,67 +274,56 @@ static irqreturn_t cdns_uart_isr(int irq, void *dev_id)
> > spin_lock(&port->lock);
> > }
> > #endif
> > -
> > - port->icount.rx++;
> > -
> > if (isrstatus & CDNS_UART_IXR_PARITY) {
> > port->icount.parity++;
> > status = TTY_PARITY;
> > - } else if (isrstatus & CDNS_UART_IXR_FRAMING) {
> > + }
> > + if ((isrstatus & CDNS_UART_IXR_FRAMING) &&
> > + !framerrprocessed) {
> > port->icount.frame++;
> > status = TTY_FRAME;
> > - } else if (isrstatus & CDNS_UART_IXR_OVERRUN) {
> > + }
> > + if (isrstatus & CDNS_UART_IXR_OVERRUN) {
> > port->icount.overrun++;
> > + tty_insert_flip_char(&port->state->port, 0,
> > + TTY_OVERRUN);
> > }
> > -
> > - uart_insert_char(port, isrstatus,
> CDNS_UART_IXR_OVERRUN,
> > - data, status);
> > + tty_insert_flip_char(&port->state->port, data, status);
> > }
> > - spin_unlock(&port->lock);
> > - tty_flip_buffer_push(&port->state->port);
> > - spin_lock(&port->lock);
> > }
> > + spin_unlock(&port->lock);
> > + tty_flip_buffer_push(&port->state->port);
> > + spin_lock(&port->lock);
> > +}
> >
> > - /* Dispatch an appropriate handler */
> > - if ((isrstatus & CDNS_UART_IXR_TXEMPTY) ==
> CDNS_UART_IXR_TXEMPTY) {
> > - if (uart_circ_empty(&port->state->xmit)) {
> > - writel(CDNS_UART_IXR_TXEMPTY,
> > - port->membase +
> CDNS_UART_IDR_OFFSET);
> > - } else {
> > - numbytes = port->fifosize;
> > - /* Break if no more data available in the UART buffer */
> > - while (numbytes--) {
> > - if (uart_circ_empty(&port->state->xmit))
> > - break;
> > - /* Get the data from the UART circular buffer
> > - * and write it to the cdns_uart's TX_FIFO
> > - * register.
> > - */
> > - writel(port->state->xmit.buf[
> > - port->state->xmit.tail],
> > - port->membase +
> CDNS_UART_FIFO_OFFSET);
> > -
> > - port->icount.tx++;
> > -
> > - /* Adjust the tail of the UART buffer and wrap
> > - * the buffer if it reaches limit.
> > - */
> > - port->state->xmit.tail =
> > - (port->state->xmit.tail + 1) &
> > - (UART_XMIT_SIZE - 1);
> > - }
> > +/**
> > + * cdns_uart_isr - Interrupt handler
> > + * @irq: Irq number
> > + * @dev_id: Id of the port
> > + *
> > + * Return: IRQHANDLED
> > + */
> > +static irqreturn_t cdns_uart_isr(int irq, void *dev_id) {
> > + struct uart_port *port = (struct uart_port *)dev_id;
> > + unsigned int isrstatus;
> >
> > - if (uart_circ_chars_pending(
> > - &port->state->xmit) < WAKEUP_CHARS)
> > - uart_write_wakeup(port);
> > - }
> > - }
> > + spin_lock(&port->lock);
> >
> > + /* Read the interrupt status register to determine which
> > + * interrupt(s) is/are active and clear them.
> > + */
> > + isrstatus = readl(port->membase + CDNS_UART_ISR_OFFSET);
> > writel(isrstatus, port->membase + CDNS_UART_ISR_OFFSET);
> >
> > - /* be sure to release the lock and tty before leaving */
> > - spin_unlock_irqrestore(&port->lock, flags);
> > + if (isrstatus & CDNS_UART_IXR_TXEMPTY) {
> > + cdns_uart_handle_tx(dev_id);
> > + isrstatus &= ~CDNS_UART_IXR_TXEMPTY;
> > + }
> > + if (isrstatus & CDNS_UART_IXR_MASK)
> > + cdns_uart_handle_rx(dev_id, isrstatus);
> >
> > + spin_unlock(&port->lock);
> > return IRQ_HANDLED;
> > }
> >
> >
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