From patchwork Fri Sep 5 19:02:47 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: 4854411 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 05A04C0338 for ; Fri, 5 Sep 2014 19:28:47 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4226E2012F for ; Fri, 5 Sep 2014 19:28:46 +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 6DE932012D for ; Fri, 5 Sep 2014 19:28:45 +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 1XPz9w-0005dw-6b; Fri, 05 Sep 2014 19:27:00 +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 1XPz9t-0005Fu-9T for linux-arm-kernel@lists.infradead.org; Fri, 05 Sep 2014 19:26:57 +0000 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1XPymw-0002uU-1M; Fri, 05 Sep 2014 21:03:14 +0200 From: Sebastian Andrzej Siewior To: linux-serial@vger.kernel.org Subject: [PATCH 12/18] tty: serial: 8250_dma: optimize the xmit path due to UART_BUG_DMA_TX Date: Fri, 5 Sep 2014 21:02:47 +0200 Message-Id: <1409943773-7874-13-git-send-email-bigeasy@linutronix.de> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1409943773-7874-1-git-send-email-bigeasy@linutronix.de> References: <1409943773-7874-1-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-20140905_122657_491650_A3FE8726 X-CRM114-Status: GOOD ( 12.41 ) X-Spam-Score: -1.7 (-) Cc: tony@atomide.com, Greg Kroah-Hartman , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, balbi@ti.com, 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=-3.6 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 Due to UART_BUG_DMA_TX the am335x has to put the first one byte into the TX FIFO to get things going. If we get to serial8250_tx_dma() via __dma_tx_complete() then the DMA engine just finished and the FIFO is full and we can't put the first byte into the TX FIFO as kick start so we leave with THRI enabled. The result is that we end up manually filling the FIFO. We could be a little better at this and try DMA once again. If it works, it works and if not we do it manually. Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_core.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 079048db8c81..7111b22de000 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1597,9 +1597,21 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) serial8250_modem_status(up); if ((!up->dma || (up->dma && up->dma->tx_err)) && (status & UART_LSR_THRE)) { - serial8250_tx_chars(up); - } + if (!up->dma) { + serial8250_tx_chars(up); + } else { + if (uart_tx_stopped(&up->port) || + uart_circ_empty(&up->port.state->xmit)) { + serial8250_tx_chars(up); + } else { + /* try again due to UART_BUG_DMA_TX+full fifo */ + dma_err = serial8250_tx_dma(up); + if (dma_err) + serial8250_tx_chars(up); + } + } + } spin_unlock_irqrestore(&port->lock, flags); return 1; }