Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S968012Ab3HIPwB (ORCPT ); Fri, 9 Aug 2013 11:52:01 -0400 Received: from mail-qa0-f44.google.com ([209.85.216.44]:58588 "EHLO mail-qa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934068Ab3HIPv6 (ORCPT ); Fri, 9 Aug 2013 11:51:58 -0400 MIME-Version: 1.0 In-Reply-To: <000e01ce94af$12710ef0$37532cd0$%jun@samsung.com> References: <86mworfzsf.fsf@void.printf.net> <000e01ce94af$12710ef0$37532cd0$%jun@samsung.com> Date: Fri, 9 Aug 2013 08:51:57 -0700 Message-ID: Subject: Re: dw_mmc: Does anyone use multiple slots? From: Doug Anderson To: Seungwon Jeon Cc: Chris Ball , Olof Johansson , James Hogan , "linux-mmc@vger.kernel.org" , Tomasz Figa , Jaehoon Chung , Grant Grundler , Alim Akhtar , Abhilash Kesavan , linux-samsung-soc , Kukjin Kim , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Sonny Rao Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2628 Lines: 55 Hi, On Thu, Aug 8, 2013 at 8:18 PM, Seungwon Jeon wrote: > On Fri, August 09, 2013, Chris Ball wrote: >> On Fri, Aug 09 2013, Olof Johansson wrote: >> > On Thu, Aug 8, 2013 at 5:16 PM, Doug Anderson wrote: >> > >> >> I guess my overall question is: if there are no actual implementations >> >> of multislot, shouldn't we kill it and simplify the code a whole lot? >> >> If someone out there has a real multislot device they can step back in >> >> and do it more correctly? >> >> >> >> Of course we need to find someone to actually go through and do the >> >> killing of multislot, but finding that person might be easier if there >> >> was some agreement that it was good to do. >> > >> > There clearly seems to be no in-tree users of multislot. If someone >> > new comes in, we have the code in the history and can revert the >> > removal (or at least use it as reference for re-introduction). >> > >> > I vote for removing it. It adds really annoying complexity for >> > something that nobody uses. >> >> I agree with Olof, for what it's worth. (The maintainers of the >> driver are Jaehoon and Seungwon, though.) > > I feel like there is no actual use case for that though origin Synopsys IP supports. > Multi-slot might be not useful in terms of performance because shared bus should be allowed. > (At least this is the way I see it, though) > As Exynos's host does so, other hosts which are introduced in Linux seems use one card per host. > If it's really not found now, I could agree on this topic. This all sounds very promising. Certainly we should wait a little longer to see if others find / respond to this thread, but otherwise we can go ahead? It's possible to do this in somewhat small steps. I think the first step is to remove num_slots and remove all loops over num_slots. That actually sounds pretty easy/small, though it will touch a lot of code. After that we can try to move things out of the separate slot structure, I think. That might be a bit of a bigger change. I can keep that as a back burner task, but I wouldn't object at all to someone else doing it! ;) The big question, though, is what to do about device tree bindings (cringe). Really bus-width, wp-gpios, and disable-wp ought to be promoted up and we should remove the "slot" subnode. ...but that of course breaks the stable API. -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/