Return-path: Received: from smtp.nokia.com ([192.100.105.134]:16495 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752613Ab0GHIzq (ORCPT ); Thu, 8 Jul 2010 04:55:46 -0400 Message-ID: <4C359256.3080704@nokia.com> Date: Thu, 08 Jul 2010 11:54:46 +0300 From: Roger Quadros MIME-Version: 1.0 To: ext Nicolas Pitre CC: ext Ohad Ben-Cohen , "linux-wireless@vger.kernel.org" , "linux-mmc@vger.kernel.org" , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux@arm.linux.org.uk" , Chikkature Rajashekar Madhusudhan , "Coelho Luciano (Nokia-MS/Helsinki)" , "akpm@linux-foundation.org" , San Mehat Subject: Re: [PATCH 11/15] wireless: wl1271: introduce platform device support References: <1278376666-3509-1-git-send-email-ohad@wizery.com> <1278376666-3509-12-git-send-email-ohad@wizery.com> <4C32EF19.1000604@nokia.com> <4C3306F4.8060907@nokia.com> <4C333E0D.2070601@nokia.com> <4C343135.1090101@nokia.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 07/07/2010 04:52 PM, ext Nicolas Pitre wrote: > On Wed, 7 Jul 2010, Roger Quadros wrote: > >> On 07/06/2010 08:42 PM, ext Nicolas Pitre wrote: >>> On Tue, 6 Jul 2010, Roger Quadros wrote: >>> >>>> OK, this is how I see it. >>>> >>>> - Treat the non-removable card as non-removable. So no need to do card >>>> detect >>>> emulation. >>>> >>>> - Treat the GPIO power enable on wl1271 as VMMC supply. Use fixed >>>> regulator >>>> framework to define this regulator& supply. Even though you mention that >>>> it >>>> is not actually a supply, it fits well in the fixed supply framework. >>>> >>>> - When the host controller is enumerated, the mmc core will power up the >>>> slot, >>>> find the sdio card, and probe the function driver (i.e. wl1271_sdio). >>>> >>>> - if interface is not in use, the function driver must release the sdio >>>> host, >>>> and this should eventually disable the vmmc supply. >>>> >>>> - Whenever the wlan interface must be brought up, wl1271_sdio, can claim >>>> the >>>> sdio host. this will cause the vmmc supply to be enabled, for as long as >>>> the >>>> interface is up. >>>> >>>> Does this address all issues? >>> >>> This is mostly all good, except that claiming/releasing the SDIO host is >>> about access to the bus. It must be claimed right before doing any IO, >>> and released right after that, even when the card is expected to remain >>> powered. This is not the proper place to hook power control. >> >> Agreed, but is it so that SDIO power may be removed between a host_release and >> claim? This appears so from omap_hsmmc host controller. > > No, it is not because a host is not claimed that power should be > dropped. The host claim/release is meant to provide exclusive access to > the card that's all. > > If the OMAP controller is dropping power to the card upon > host->disable() then it is wrong. AFAICS only the OMAP controller is > playing such games at the moment and I suspect the semantics might not > be all right. Shutting down the _controller_ when it is idle might be a > good thing, but not power to the _card_. Only the function driver might > know when it is fine to lose power. > > I completely agree with you Nicolas. omap_hsmmc needs to be fixed so that it does not control MMC/SDIO slot supply voltage. It should deal with only the mmc controller power savings and not the card/function power savings. regards, -roger