From patchwork Fri Aug 15 17:42:34 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 4728731 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id EA3E89F38D for ; Fri, 15 Aug 2014 17:46:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0A0F02016C for ; Fri, 15 Aug 2014 17:46:56 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 96EAA20117 for ; Fri, 15 Aug 2014 17:46:54 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1XILXl-0001jl-9E; Fri, 15 Aug 2014 17:44:01 +0000 Received: from galois.linutronix.de ([2001:470:1f0b:db:abcd:42:0:1]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XILX9-0001R5-El for linux-arm-kernel@lists.infradead.org; Fri, 15 Aug 2014 17:43:24 +0000 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1XILWg-0006sE-SV; Fri, 15 Aug 2014 19:42:55 +0200 From: Sebastian Andrzej Siewior To: linux-serial@vger.kernel.org Subject: [PATCH 06/15] tty: serial: 8250_dma: handle error on TX submit Date: Fri, 15 Aug 2014 19:42:34 +0200 Message-Id: <1408124563-31541-7-git-send-email-bigeasy@linutronix.de> X-Mailer: git-send-email 2.0.1 In-Reply-To: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> References: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1, SHORTCIRCUIT=-0.0001 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140815_104323_726196_94F59D48 X-CRM114-Status: GOOD ( 14.70 ) X-Spam-Score: -0.7 (/) Cc: tony@atomide.com, Greg Kroah-Hartman , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, balbi@ti.com, Vinod Koul , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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_core.c | 2 +- drivers/tty/serial/8250/8250_dma.c | 30 +++++++++++++++++++++++++----- include/linux/serial_8250.h | 1 + 3 files changed, 27 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index ab003b6..7498ce1 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1600,7 +1600,7 @@ 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_tx_err) && (status & UART_LSR_THRE)) serial8250_tx_chars(up); spin_unlock_irqrestore(&port->lock, flags); diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 148ffe4..5c59b15 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) { + p->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 (p->dma_tx_err) { + p->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: + p->dma_tx_err = 1; + return ret; } EXPORT_SYMBOL_GPL(serial8250_tx_dma); diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index b161eee..02e82dc 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -85,6 +85,7 @@ struct uart_8250_port { unsigned char mcr_force; /* mask of forced bits */ unsigned char cur_iotype; /* Running I/O type */ unsigned char rpm_tx_active; + unsigned char dma_tx_err; /* * Some bits in registers are cleared on a read, so they must