From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART Date: Tue, 12 Apr 2016 19:50:24 +0300 Message-ID: <1460479824.6620.121.camel@linux.intel.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1460478320.19152.92.camel@nexus-software.ie> Sender: linux-kernel-owner@vger.kernel.org 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" List-Id: linux-serial@vger.kernel.org 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: > >=20 > > On Mon, Apr 11, 2016 at 6:33 PM, Bryan O'Donoghue > > wrote: > > >=20 > > > On Thu, 2016-04-07 at 23:37 +0300, Andy Shevchenko wrote: > > >=20 > > > 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). > >=20 > > >=20 > > > >=20 > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0lpss->dma_maxburst =3D= 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=C2=A0 > > 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 =46IFO/2, which is exactly 8 bytes. --=20 Andy Shevchenko Intel Finland Oy