Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751918AbbEGUYu (ORCPT ); Thu, 7 May 2015 16:24:50 -0400 Received: from Chamillionaire.breakpoint.cc ([80.244.247.6]:56480 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751158AbbEGUYq (ORCPT ); Thu, 7 May 2015 16:24:46 -0400 Date: Thu, 7 May 2015 22:24:39 +0200 From: Sebastian Andrzej Siewior To: gregkh@linuxfoundation.org Cc: Sebastian Andrzej Siewior , jiwang , jslaby@suse.cz, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, anton_bondarenko@mentor.com, dirk.behme@de.bosch.com, Nicolae Rosia , Fabio Estevam Subject: [PATCH] serial: imx: Revert "initialized DMA w/o HW flow enabled" Message-ID: <20150507202439.GA4717@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3060 Lines: 80 From: Sebastian Andrzej Siewior This basically reverts commit 068500e08dc8 ("serial: imx: initialized DMA w/o HW flow enabled") simply because it does not work as expected without additional magic which I am not aware of. The DMA mode is only used for non-console UARTs so the "standard" boot test won't notice this. I tested it on various IMX6 (S and Q) boards and the default SDMA firmware that is included in ROM does work properly. The SDMA interrupt counter does not stop increment (which means the SDMA does not stop working or the ACK is working) and I see a lot of 0x00 (sometimes other bytes) which are added to the tty buffer which are not part of the data transfer. Jiada claimed that there is a firmware which makes it work but failed to provide me a link to the firmware. All he said was that it can not be shipped as part of the kernel due to license issues. I've found a firmware blob in the FSL-tree but this firmware causes only TTY-overflows an *no* data is transmitted. Currently I see no other way out. Fixes: 068500e08dc8 ("serial: imx: initialized DMA w/o HW flow enabled") Cc: Fabio Estevam Cc: Jiada Wang Cc: nicolae.rosia@gmail.com Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/imx.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 8aff0b4d8ddf..e686c75fa4dc 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1113,11 +1113,6 @@ static int imx_startup(struct uart_port *port) writel(temp & ~UCR4_DREN, sport->port.membase + UCR4); - /* Can we enable the DMA support? */ - if (is_imx6q_uart(sport) && !uart_console(port) && - !sport->dma_is_inited) - imx_uart_dma_init(sport); - spin_lock_irqsave(&sport->port.lock, flags); /* Reset fifo's and state machines */ i = 100; @@ -1308,6 +1303,17 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios, } else { ucr2 |= UCR2_CTSC; } + + /* + * Can we enable the DMA support? Be aware that + * at least IMX6 needs to load external SDMA firmware in + * order work properly. The in-ROM firmware is not + * wokring properly. + */ + if ((ucr2 & UCR2_CTSC) && is_imx6q_uart(sport) && + !uart_console(port) && !sport->dma_is_inited) + imx_uart_dma_init(sport); + } else { termios->c_cflag &= ~CRTSCTS; } @@ -1424,6 +1430,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios, if (UART_ENABLE_MS(&sport->port, termios->c_cflag)) imx_enable_ms(&sport->port); + if (sport->dma_is_inited && !sport->dma_is_enabled) + imx_enable_dma(sport); spin_unlock_irqrestore(&sport->port.lock, flags); } -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/