From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932263AbcE0C1J (ORCPT ); Thu, 26 May 2016 22:27:09 -0400 Received: from lucky1.263xmail.com ([211.157.147.135]:55206 "EHLO lucky1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932117AbcE0C1H (ORCPT ); Thu, 26 May 2016 22:27:07 -0400 X-263anti-spam: KSV:0; X-MAIL-GRAY: 1 X-MAIL-DELIVERY: 0 X-KSVirus-check: 0 X-ABS-CHECKED: 4 X-ADDR-CHECKED: 0 X-RL-SENDER: shawn.lin@rock-chips.com X-FST-TO: linux-rockchip@lists.infradead.org X-SENDER-IP: 58.22.7.114 X-LOGIN-NAME: shawn.lin@rock-chips.com X-UNIQUE-TAG: <4f0a5b3d498ae948b42ecf92f197c4ba> X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Subject: Re: [RFC PATCH 2/2] mmc: dw_mmc: check card present before starting request To: Jaehoon Chung , Ulf Hansson References: <1464232091-24882-1-git-send-email-shawn.lin@rock-chips.com> <57479A84.4080207@samsung.com> Cc: shawn.lin@rock-chips.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Doug Anderson , linux-rockchip@lists.infradead.org From: Shawn Lin Message-ID: <6c5f8e6c-efbc-667e-2a7b-00381e8a5646@rock-chips.com> Date: Fri, 27 May 2016 10:26:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <57479A84.4080207@samsung.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jaehoon, On 2016/5/27 8:53, Jaehoon Chung wrote: > Hi Shawn, > > On 05/26/2016 12:08 PM, Shawn Lin wrote: >> The main reason to add this check is to avoid unnecessary >> mmc_request if the card is removed. Although we have already >> check this in dw_mci_handle_cd for runtime usage of sd card and >> dw_mci_init_slot for noremovable devices, but there is a timing >> gap before it really calls dw_mci_get_cd as mmc_detect_change needs >> some delay here. > > What's unnecessary mmc_request? the on-going read/write/ and the corresponding sbc like cmd13, etc. > >> >> Another gain here is that we could save some checkings of card status >> after sd card been removed. >> >> Signed-off-by: Shawn Lin >> --- >> >> drivers/mmc/host/dw_mmc.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c >> index cb30e91..2940d24 100644 >> --- a/drivers/mmc/host/dw_mmc.c >> +++ b/drivers/mmc/host/dw_mmc.c >> @@ -105,6 +105,7 @@ struct idmac_desc { >> static bool dw_mci_reset(struct dw_mci *host); >> static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset); >> static int dw_mci_card_busy(struct mmc_host *mmc); >> +static int dw_mci_get_cd(struct mmc_host *mmc); >> >> #if defined(CONFIG_DEBUG_FS) >> static int dw_mci_req_show(struct seq_file *s, void *v) >> @@ -1248,6 +1249,8 @@ static void dw_mci_request(struct mmc_host *mmc, struct mmc_request *mrq) >> >> WARN_ON(slot->mrq); >> >> + dw_mci_get_cd(mmc); >> + > > If my understanding is right, it can be replaced > > if (!test_bit(DW_MMC_CARD_PRESENT, &slot->flags)) > > to > > if (!dw_mci_get_cd(mmc)) yeah~ It looks better. > > > Best Regards, > Jaehoon Chung > > > >> /* >> * The check for card presence and queueing of the request must be >> * atomic, otherwise the card could be removed in between and the >> > > > > -- Best Regards Shawn Lin