From mboxrd@z Thu Jan 1 00:00:00 1970 From: bigeasy@linutronix.de (Sebastian Andrzej Siewior) Date: Fri, 5 Sep 2014 21:02:44 +0200 Subject: [PATCH 09/18] tty: serial: 8250_dma: handle error on TX submit In-Reply-To: <1409943773-7874-1-git-send-email-bigeasy@linutronix.de> References: <1409943773-7874-1-git-send-email-bigeasy@linutronix.de> Message-ID: <1409943773-7874-10-git-send-email-bigeasy@linutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Right now it is possible that serial8250_tx_dma() fails and returns -EBUSY. The caller (serial8250_start_tx()) will then enable UART_IER_THRI which will generate an interrupt once the TX FIFO is empty. In serial8250_handle_irq() nothing will happen because up->dma is set and so serial8250_tx_chars() won't be invoked. We end up with plenty of interrupts and some "too much work for irq" output. This patch introduces dma_tx_err in struct uart_8250_port to signal that the last invocation of serial8250_tx_dma() failed so we can fill the TX FIFO manually. Should the next invocation of serial8250_start_tx() succeed then the dma_tx_err flag along with the THRI bit is removed and DMA only usage may continue. Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250.h | 1 + drivers/tty/serial/8250/8250_core.c | 4 +++- drivers/tty/serial/8250/8250_dma.c | 30 +++++++++++++++++++++++++----- 3 files changed, 29 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index 1bcb4b2141a6..a63d198f8d03 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -41,6 +41,7 @@ struct uart_8250_dma { size_t tx_size; unsigned char tx_running:1; + unsigned char tx_err: 1; }; struct old_serial_port { diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index e8df7cd85ba7..2101134e5031 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1592,8 +1592,10 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) status = serial8250_rx_chars(up, status); } serial8250_modem_status(up); - if (!up->dma && (status & UART_LSR_THRE)) + if ((!up->dma || (up->dma && up->dma->tx_err)) && + (status & UART_LSR_THRE)) { serial8250_tx_chars(up); + } spin_unlock_irqrestore(&port->lock, flags); return 1; diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 148ffe4c232f..69e54abb6e71 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -36,8 +36,16 @@ static void __dma_tx_complete(void *param) if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) uart_write_wakeup(&p->port); - if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) - serial8250_tx_dma(p); + if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) { + int ret; + + ret = serial8250_tx_dma(p); + if (ret) { + dma->tx_err = 1; + p->ier |= UART_IER_THRI; + serial_port_out(&p->port, UART_IER, p->ier); + } + } spin_unlock_irqrestore(&p->port.lock, flags); } @@ -69,6 +77,7 @@ int serial8250_tx_dma(struct uart_8250_port *p) struct uart_8250_dma *dma = p->dma; struct circ_buf *xmit = &p->port.state->xmit; struct dma_async_tx_descriptor *desc; + int ret; if (uart_tx_stopped(&p->port) || dma->tx_running || uart_circ_empty(xmit)) @@ -80,8 +89,10 @@ int serial8250_tx_dma(struct uart_8250_port *p) dma->tx_addr + xmit->tail, dma->tx_size, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK); - if (!desc) - return -EBUSY; + if (!desc) { + ret = -EBUSY; + goto err; + } dma->tx_running = 1; @@ -94,8 +105,17 @@ int serial8250_tx_dma(struct uart_8250_port *p) UART_XMIT_SIZE, DMA_TO_DEVICE); dma_async_issue_pending(dma->txchan); - + if (dma->tx_err) { + dma->tx_err = 0; + if (p->ier & UART_IER_THRI) { + p->ier &= ~UART_IER_THRI; + serial_out(p, UART_IER, p->ier); + } + } return 0; +err: + dma->tx_err = 1; + return ret; } EXPORT_SYMBOL_GPL(serial8250_tx_dma); -- 2.1.0