From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dinh Nguyen Subject: [RFC RESEND] serial: 8250: fix regression in 8250 uart driver Date: Mon, 13 Jun 2016 21:59:49 -0500 Message-ID: <575F7325.3030907@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: andriy.shevchenko@linux.intel.com Cc: heikki.krogerus@linux.intel.com, peter@hurleysoftware.com, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org List-Id: linux-serial@vger.kernel.org Apologies, but my original email bounced for Andy and Heikki, resending. ---- Hi Andy, I saw that you have discovered that commit ec5a11a91eec ("serial: 8250: Validate dmaengine rx chan meets requirements") introduced a regression in the 8250 uart driver. For SoCFPGA platform, I am seeing this error: [ 5.541751] ttyS0 - failed to request DMA Reverting the commit ec5a11a91eec removes the error. I saw that you started the discussion, but I didn't see that a patch was included[1]. The following patch seems to fix the error, but I'm not sure if it's the same fix that you had in mind. Thanks, Dinh [1] http://marc.info/?l=linux-serial&m=146254187602862&w=2 ---------------8<------------ diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 7f33d1c..847a203 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -176,7 +176,7 @@ int serial8250_request_dma(struct uart_8250_port *p) ret = dma_get_slave_caps(dma->rxchan, &caps); if (ret) goto release_rx; - if (!caps.cmd_pause || !caps.cmd_terminate || + if ((!caps.cmd_pause || !caps.cmd_terminate) && caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { ret = -EINVAL; goto release_rx;