From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: [PATCH 2/5] i2c: sh_mobile: add DMA support Date: Mon, 15 Dec 2014 10:32:00 +0100 Message-ID: References: <1415355104-2031-1-git-send-email-wsa@the-dreams.de> <2462101.Er8OZg9N24@avalon> <20141211214732.GC21482@katana> <1729516.HWbfnj3Cpn@avalon> <20141215064306.GN16827@intel.com> <20141215090628.GB1031@katana> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20141215090628.GB1031@katana> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: Vinod Koul , Laurent Pinchart , Magnus Damm , Linux I2C , Linux-sh list , Simon Horman , dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org Hi Wolfram, On Mon, Dec 15, 2014 at 10:06 AM, Wolfram Sang wrote: >> Solutions under consideration: >> 1. Wolfram posted a patch to make i2c-sh_mobile fall back to PIO, >> and retry DMA initialization in every request, so it will switch to >> DMA when it becomes available. But this is suboptimal, as it adds >> overhead to every request (and DMA may never become available in >> case 2). > > Still, I'd think I should repost my patches with your comments > addressed. It does add a bit of overhead IF the dmaengine core is > compiled in AND the driver for the DMA hardware is not. Well, yeah. On > the other hand, it fixes the regression that the driver is not even > loaded in that case (because it currently will be deferred endlessly). > > What do you think? I think it doesn't hurt to repost, now more people understand the intrinsics of the problem. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds