From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arend van Spriel Subject: Re: [PATCH V4 01/15] mmc: host: Add facility to support re-tuning Date: Thu, 2 Apr 2015 12:30:49 +0200 Message-ID: <551D1A59.5060803@broadcom.com> References: <1427489863-9050-1-git-send-email-adrian.hunter@intel.com> <1427489863-9050-2-git-send-email-adrian.hunter@intel.com> <551BDAEA.20405@intel.com> <551C0A4C.9020602@broadcom.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-gw2-out.broadcom.com ([216.31.210.63]:1826 "EHLO mail-gw2-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751149AbbDBKaz (ORCPT ); Thu, 2 Apr 2015 06:30:55 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Ulf Hansson Cc: Adrian Hunter , linux-mmc , Aaron Lu , Philip Rakity , Al Cooper On 04/02/15 10:43, Ulf Hansson wrote: > [...] >>>>> - ability to hold off re-tuning if the card is busy >>>> >>>> >>>> What do you mean by "card is busy"? >>> >>> >>> I guess, more accurately, any time the card is in a state that is >>> incapable >>> of supporting re-tuning. For example: >>> - DAT0 busy >> >> >> This state is not specific to re-tuning. An SDIO device can keep DAT0 busy >> at which the host controller can not start another request. > > Not entirely true. Some commands are allowed during this period, for > example CMD13 (which doesn't exist for SDIO) Yeah. I was wondering whether to mention that. > Anyway, I get the point. Thanks! > >> >>> - between dependent commands like erase start, end, etc >>> - card is asleep >>> Also SDIO cards can have a custom sleep state where tuning won't work. >> >> >> Our SDIO wifi device has such a state and it can only come out of it upon >> CMD52 write or CMD14 (ExitSleep). > > So how will the mmc core know about these states? I guess we will > require SDIO func drivers to deal with enable/disable or hold/release > of re-tuning then? This is actually why in the past we tried to only kick off retuning before a request that requires use of data line(s) so mmc core (or sdhci) would not do re-tuning when SDIO func used CMD52 to wakeup the device. I never tried CMD14 approach and not even sure from which spec it comes (maybe eMMC). > I don't like this, but if there is no other way... Also, we must be > very careful on which API we exports for SDIO func drivers to use. The > can easily be misinterpreted. > > [...] > > Kind regards > Uffe Regards, Arend