Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756980AbcDLQtk (ORCPT ); Tue, 12 Apr 2016 12:49:40 -0400 Received: from mga02.intel.com ([134.134.136.20]:47080 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756702AbcDLQth (ORCPT ); Tue, 12 Apr 2016 12:49:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,475,1455004800"; d="scan'208";a="943620730" Message-ID: <1460479824.6620.121.camel@linux.intel.com> Subject: Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART From: Andy Shevchenko To: "Bryan O'Donoghue" , Andy Shevchenko Cc: Vinod Koul , "linux-kernel@vger.kernel.org" , dmaengine , Greg Kroah-Hartman , "Puustinen, Ismo" , Heikki Krogerus , "linux-serial@vger.kernel.org" Date: Tue, 12 Apr 2016 19:50:24 +0300 In-Reply-To: <1460478320.19152.92.camel@nexus-software.ie> References: <1460061433-63750-1-git-send-email-andriy.shevchenko@linux.intel.com> <1460061433-63750-13-git-send-email-andriy.shevchenko@linux.intel.com> <1460388795.19152.38.camel@nexus-software.ie> <1460478320.19152.92.camel@nexus-software.ie> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.1-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1312 Lines: 37 On Tue, 2016-04-12 at 17:25 +0100, Bryan O'Donoghue wrote: > On Mon, 2016-04-11 at 18:51 +0300, Andy Shevchenko wrote: > > > > On Mon, Apr 11, 2016 at 6:33 PM, Bryan O'Donoghue > > wrote: > > > > > > On Thu, 2016-04-07 at 23:37 +0300, Andy Shevchenko wrote: > > > > > > Preface. I tried this on Galileo and it appears to work. I'll do > > > some > > > throughput testing to verify but, initially the results are > > > positive :) > > I submitted (and pushed into my branch) a bit changed version (see > > my > > v2). > > > > > > > > > > > > > +       lpss->dma_maxburst = 8; > > > Are these dwords ? If those are bytes then the maxburst value > > > looks > > > small. In the BSP the max burst is 32 bytes. > > max_burst is in items of given size (here is 32 bytes for memory > > and  > > 8 > I haven't read your V2 yet but on this, I'd suggest raising the burst > size to 32 bytes for UART (no higher) we found during bringup that > larger sizes "fall-over and die" but, anything up to 32 bytes is OK - > and therefore you should be able to reduce the number of > bursts/interrupts etc. It can't be more that FIFO size and recommendation as far as I know is FIFO/2, which is exactly 8 bytes. -- Andy Shevchenko Intel Finland Oy