Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752044AbaKYFg1 (ORCPT ); Tue, 25 Nov 2014 00:36:27 -0500 Received: from mail-vc0-f174.google.com ([209.85.220.174]:41051 "EHLO mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751995AbaKYFgG (ORCPT ); Tue, 25 Nov 2014 00:36:06 -0500 MIME-Version: 1.0 In-Reply-To: <5473EB8B.3000803@rock-chips.com> References: <1415109789-7046-1-git-send-email-addy.ke@rock-chips.com> <1415678573-6093-1-git-send-email-addy.ke@rock-chips.com> <5464152E.7040209@rock-chips.com> <5473EB8B.3000803@rock-chips.com> Date: Mon, 24 Nov 2014 21:36:04 -0800 X-Google-Sender-Auth: 4_XtvK2dWCi3rZcrnKllgsru5jc Message-ID: Subject: Re: [PATCH] mmc: dw_mmc: try pick the exact same voltage as vmmc for vqmmc From: Doug Anderson To: Addy Cc: Ulf Hansson , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Randy Dunlap , "tgih.jun@samsung.com" , Jaehoon Chung , Chris Ball , Dinh Nguyen , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Olof Johansson , Sonny Rao , Alexandru Stan , "devicetree@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-mmc , "linux-arm-kernel@lists.infradead.org" , "open list:ARM/Rockchip SoC..." , "zhenfu.fang" , Eddie Cai , lintao , chenfen , zyf , Jianqun Xu , Tao Huang , Chris Zhong , =?UTF-8?B?5aea5pm65oOF?= , han jiang , Kever Yang , zhangqing , Lin Huang Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Addy, On Mon, Nov 24, 2014 at 6:38 PM, Addy wrote: >> In worst case scenario, VDD = 3.6V and VIO = 2.7V. That gives as the >> factor of 0.75, thus we are inside spec but without margins. > > * From eMMC4.5 spec: > 1. (VDDF)vcc: Supply voltage for flash memory, which is 2.7v -- 3.3v > 2. (VDD)vccq: Supply voltage for memory controller, which is 1.7v -- > 1.95v and 2,7v -- 3.6v > > * And from RK3288 datasheet: > Digtial GPIO Power(SDMMC0_VDD --> vccq) is 3.0v -- 3.6v and 1.62v - 1.98v > > So I think: > 3.3v: (2.7v < vccq < 3.6v) && (3.0v < vccq < 3.6v) ==> (3.0v < vccq < > 3.6v) > 1.8v: (1.7v < vccq < 1.95v) && (1.62v < vccq < 1.98v) ==> (1.7v < vccq < > 1.95v) > > and (2.7v < vcc < 3.3v) > > * And according to our hardware engineer: > All of supply voltage must have +/- 10% cushion. > > * And we have found in some worse card that there is 200mv voltage collapse > when these card is insert. > > So I think the best resolution is that vcc and vccq is configurable int dt > table. Ah, interesting. ...so what we really need to be able to do is to say that the regulator we for vqmmc have supports the ranges 3.0V - 3.3V and 1.7V - 1.95V but not anything in between 1.95V ad 3.0V. I have no idea how to express that in the regulator framework. Technically you could take the IO Voltage Domains code (responsible for choosing the 1.8V range or the 3.3V range) and have it communicate the requirements to the regulator framework if you could figure out how to communicate them. ...of course if you implemented my suggestion of keeping vqmmc as the highest voltage <= vmmc then maybe the whole point is moot and we don't have to figure it out. Just make sure that vmmc never goes below 3.0V. -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/