Return-path: Received: from smtp.nokia.com ([192.100.105.134]:36561 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754219Ab0GFTvw (ORCPT ); Tue, 6 Jul 2010 15:51:52 -0400 Message-ID: <4C338927.5020400@nokia.com> Date: Tue, 06 Jul 2010 22:51:03 +0300 From: Adrian Hunter MIME-Version: 1.0 To: Nicolas Pitre CC: "Quadros Roger (Nokia-MS/Helsinki)" , 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: Nicolas Pitre wrote: > On Tue, 6 Jul 2010, Roger Quadros wrote: > >> On 07/06/2010 03:53 PM, ext Ohad Ben-Cohen wrote: >>> Hi Roger, >>> >>> On Tue, Jul 6, 2010 at 1:35 PM, Roger Quadros >>> wrote: >>>> My point is that shouldn't this be handled by SDIO core? >>> Care to explain what you mean / give a code example ? >> If the Power enable GPIO can be treated as SDIO slot supply (i.e. vmmc), then >> the SDIO/MMC core should tackle it, just like it deals with supply for slots >> with removable cards. > > Exact. > >>> You need card detect events in order to trigger card& sdio function >>> initialization and removals. > > Why would you trigger function initialization and removal? Just to turn > off power? That's a bit like pulling off the battery from your laptop > when you want to suspend it. There is a better way to go about things. > >>> Please share any alternative approach you may be thinking on. >> 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. > > Another function pair would be needed instead, which would do almost > like the suspend/resume code is already doing. Something like: > > /* > * Indicate to the core SDIO layer that we're not requiring that the > * function remain powered. If all functions for the card are in the > * same "no power" state, then the host controller can remove power from > * the card. Note: the function driver must preserve hardware states if > * necessary. > */ > int sdio_release_power(struct sdio_func *func); > > /* > * Indicate to the core SDIO layer that we want power back for this > * SDIO function. The power may or may not actually have been removed > * since last call to sdio_release_power(), so the function driver must > * not assume any preserved state at the hardware level and re-perform > * all the necessary hardware config. This function returns 0 when > * power is actually restored, or some error code if this cannot be > * achieved. One error reason might be that the card is no longer > * available on the bus (was removed while powered down and card > * detection didn't trigger yet). > */ > int sdio_claim_power(struct sdio_func *func); > > That's it. When the network interface is down and the hardware is not > needed, you call sdio_release_power(). When the request to activate the > network interface is received, you call sdio_claim_power() and configure > the hardware appropriately. If sdio_claim_power() returns an error, > then you just return an error to the network request, and eventually the > driver's remove method will be called if this is indeed because the card > was removed. > > In the core SDIO code, this is almost identical to a suspend/resume > request, except that the request comes from the function driver instead > of the core MMC code. For eMMC in omap_hsmmc, this is all done via claim_host / release_host which call ->enable() / ->disable() methods. omap_hsmmc makes use of mmc_power_restore_host() which calls host->bus_ops->power_restore() which is not implemented for SDIO, but for MMC and SD it reinitializes the card. Set omap2_hsmmc_info mmc[x] {.nonremovable=true, .power_saving=true} and implement host->bus_ops->power_restore() for SDIO, then the power will go off 9 seconds after sdio_release_host() is called. Then tweak omap_hsmmc so that it doesn't wait 9 seconds for the SDIO case > > > Nicolas > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >