From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailrelay005.isp.belgacom.be (mailrelay005.isp.belgacom.be [195.238.6.171]) by ozlabs.org (Postfix) with ESMTP id DDCA0DDE23 for ; Thu, 18 Dec 2008 21:23:52 +1100 (EST) From: Laurent Pinchart To: "Remi Lefevre" Subject: Re: FHCI driver adaptation for CPM2 Date: Thu, 18 Dec 2008 11:23:48 +0100 References: <4e0b9cb00812170710n3374d558xab3584dc61980756@mail.gmail.com> <200812171633.58081.laurentp@cse-semaphore.com> <4e0b9cb00812171227g47647d31ufaec827ddbab0232@mail.gmail.com> In-Reply-To: <4e0b9cb00812171227g47647d31ufaec827ddbab0232@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Message-Id: <200812181123.48550.laurentp@cse-semaphore.com> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Remi, On Wednesday 17 December 2008 21:27:49 Remi Lefevre wrote: > >> Also 40% seems quite a lot, even at 1000Hz interruptions, an idea how > >> much does the CRC computation contribute in this CPU hogging ? > > > > I haven't measured that, but probably not much. The biggest CPU time > > eater isn't the SOF generation interrupt but the USB packet handling > > code. The CPM2 USB host controller is really too low-level to be usable > > (except maybe for specific applications). Comparing the OHCI/UHCI/EHCI > > and FHCI controllers is akin to bit like comparing a full 16550 UART > > with a software bit-bang implementation. You can get around with it, it > > might work for your specific application, but you shouldn't try a full > > speed 115200bds communication while computing a CPU-hungry physical > > simulation. > > That's what I was afraid of. I now understand clearly why you didn't expect > that much better performance with CPM3 in a past message > (http://ozlabs.org/pipermail/linuxppc-embedded/2008-May/030508.html). > Still, as you said, it can have some use for specific applications. > > Do you remember the throughput you were able to reach with this cpu > overhead ? I'm sorry I don't. Best regards, -- Laurent Pinchart CSE Semaphore Belgium Chaussee de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 F +32 (2) 387 42 75