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: Wed, 29 Dec 2010 11:35:33 +0100 Message-ID: <4D1B0EF5.4080206@arndnet.de> References: <1293535523-19191-1-git-send-email-arnd@arndnet.de> <4D19EE1C.9050801@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]:39414 "EHLO mail.unitix.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750962Ab0L2Kff (ORCPT ); Wed, 29 Dec 2010 05:35:35 -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 15:24, schrieb Ohad Ben-Cohen: >>> Do you mean that your card is always powered on regardless of >>> mmc_power_off() invocations ? >> >> Yes, it seems so. > > Ok, thanks for letting us know. > > It bothered me that we didn't understand the issue you had, but now it > seems that MMC_CAP_POWER_OFF_CARD is the right solution for you as > well. > >> 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? > > Well, with some SDIO cards, the host controller can use the recently > added aggressive clock gating framework to stop the clock on > inactivity, and not wait until the card is powered off. > > Currently that clock gating framework is still disabled for SDIO > cards, but this is just temporary until we sort out how to use it > safely for SDIO as well. So you suggest to don't set MMC_CAP_POWER_OFF_CARD for the boards which keep the card powered, but instead wait for the clock gating framework? > For example, the wl1271 card has asynchronous interrupts (via external > irq) so we can safely stop its clock on inactivity. > > Do you know if that's possible with your card as well ? I don't think so, the card is a normal SDIO card which plugs into a normal MMC/SD slot, no extra pins or such. However SDIO IRQs are available, but you don't mean that, do you? Thanks, Arnd