From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Hannemann Subject: Re: [PATCH] [RFC] mmc: perform SDIO reset on power restore of host Date: Tue, 28 Dec 2010 15:03:08 +0100 Message-ID: <4D19EE1C.9050801@arndnet.de> References: <1293535523-19191-1-git-send-email-arnd@arndnet.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from slowhand.arndnet.de ([88.198.19.76]:33384 "EHLO mail.unitix.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752156Ab0L1ODQ (ORCPT ); Tue, 28 Dec 2010 09:03:16 -0500 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Ohad Ben-Cohen Cc: linux-mmc@vger.kernel.org, Chris Ball Hi Ohad, Am 28.12.2010 13:45, schrieb Ohad Ben-Cohen: > On Tue, Dec 28, 2010 at 1:25 PM, Arnd Hannemann wrote: >> On some boards card power is hard wired to the slot >> and active regardless of host controller state. > ... >> This was observed on AP4EVB with tmio_mmc and a b43 based >> SDIO card: >> http://marc.info/?l=linux-mmc&m=128854536521274&w=2 > > Do you mean that your card is always powered on regardless of > mmc_power_off() invocations ? Yes, it seems so. > I always wondered why SDIO runtime PM didn't work with your card, so > thanks for the follow up on this. > > That said, if you card can't be powered down, then it shouldn't be > MMC_CAP_POWER_OFF_CARD at all (which literally means that the card can > be powered down). > > And if it isn't MMC_CAP_POWER_OFF_CARD, then runtime PM will stay > disabled for the card, so the problem you describe can't happen. Even if the card is kept powered, when mmc_power_off() is called, the host controller will stop the SD bus clock. So I believe at least some power is saved this way and MMC_CAP_POWER_OFF_CARD makes sense? Thanks, Arnd