From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751807AbaHRPPa (ORCPT ); Mon, 18 Aug 2014 11:15:30 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:40940 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750911AbaHRPP2 (ORCPT ); Mon, 18 Aug 2014 11:15:28 -0400 Message-ID: <53F21885.605@hurleysoftware.com> Date: Mon, 18 Aug 2014 11:15:17 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Tony Lindgren , Sebastian Andrzej Siewior CC: Lennart Sorensen , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, balbi@ti.com, Vinod Koul , Greg Kroah-Hartman Subject: Re: [PATCH v7] 8250-core based serial driver for OMAP + DMA References: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> <20140815181704.GH17769@csclub.uwaterloo.ca> <53EE5BF8.3010007@linutronix.de> <20140815202826.GC9239@atomide.com> In-Reply-To: <20140815202826.GC9239@atomide.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/15/2014 04:28 PM, Tony Lindgren wrote: > * Sebastian Andrzej Siewior [140815 12:16]: >> On 08/15/2014 08:17 PM, Lennart Sorensen wrote: >> >>> Are you saying that with the new driver you have to respond to the RX >>> irq faster than before to avoid overflows? It is not quite clear. >> >> Yes. The irq fires 46 bytes giving you 16 bytes buffer before overflow >> vs 63 bytes buffer the old one had. >> >>> I do think 40000 interrupts to handle 40000 bytes of date does seem a >>> tad inefficient, so dropping to 854 looks a lot nicer. Was the omap >>> driver not using the fifo trigger levels at all? >> >> It configured the trigger levels to 1 for RX and 16 for TX. > > Hmm that weird RX trigger level is a workaround for lost characters. > > See commit 0ba5f66836 (tty: serial: OMAP: use a 1-byte RX FIFO > threshold in PIO mode :) That commit looks like it should have been specific to the silicon exhibiting the rx timeout bug. Regards, Peter Hurley