Hi, > -----Original Message----- > From: Peter Hurley [mailto:peter@xxxxxxxxxxxxxxxxxx] > Sent: Monday, August 17, 2015 9:26 PM > To: Michal Simek > Cc: linux-kernel@xxxxxxxxxxxxxxx; monstr@xxxxxxxxx; Anirudha Sarangi; Soren > Brinkmann; Jiri Slaby; linux-serial@xxxxxxxxxxxxxxx; Greg Kroah-Hartman; linux- > arm-kernel@xxxxxxxxxxxxxxxxxxx > 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@xxxxxxxxxx> > > > > 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@xxxxxxxxxx> > > Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx> > > --- > > > > 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; > > } > > > > This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. 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