From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10657C433EF for ; Wed, 16 Mar 2022 09:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355020AbiCPJzv (ORCPT ); Wed, 16 Mar 2022 05:55:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355006AbiCPJzt (ORCPT ); Wed, 16 Mar 2022 05:55:49 -0400 Received: from out28-73.mail.aliyun.com (out28-73.mail.aliyun.com [115.124.28.73]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1DC5B33880; Wed, 16 Mar 2022 02:54:34 -0700 (PDT) X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07436528|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_regular_dialog|0.0161911-0.00387286-0.979936;FP=0|0|0|0|0|-1|-1|-1;HT=ay29a033018047199;MF=michael@allwinnertech.com;NM=1;PH=DS;RN=8;RT=8;SR=0;TI=SMTPD_---.N5pKMoy_1647424463; Received: from 172.30.10.142(mailfrom:michael@allwinnertech.com fp:SMTPD_---.N5pKMoy_1647424463) by smtp.aliyun-inc.com(33.13.195.200); Wed, 16 Mar 2022 17:54:31 +0800 Message-ID: <32b29790-eb5c-dac0-1f91-aede38220914@allwinnertech.com> Date: Wed, 16 Mar 2022 17:54:23 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH] mmc: block: enable cache-flushing when mmc cache is on Content-Language: en-GB To: Avri Altman , Adrian Hunter , "ulf.hansson@linaro.org" , "beanhuo@micron.com" , "porzio@gmail.com" Cc: "linux-mmc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , allwinner-opensource-support References: <20220312044315.7994-1-michael@allwinnertech.com> <83edf9a1-1712-5388-a3fa-d685f1f581df@intel.com> <88e53cb9-791f-ee58-9be8-76ae9986e0e2@allwinnertech.com> From: Michael Wu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/03/2022 17:37, Avri Altman wrote: >> On 14/03/2022 14:54, Adrian Hunter wrote: >>> On 12/03/2022 06:43, Michael Wu wrote: >>>> The mmc core enable cache on default. But it only enables >>>> cache-flushing when host supports cmd23 and eMMC supports reliable >> write. >>>> For hosts which do not support cmd23 or eMMCs which do not support >>>> reliable write, the cache can not be flushed by `sync` command. >>>> This may leads to cache data lost. >>>> This patch enables cache-flushing as long as cache is enabled, no >>>> matter host supports cmd23 and/or eMMC supports reliable write or not. >>>> >>> >>> Fixes tag? >>> >> >> Hi Adrian, >> My patch intend to fix the cache problem brought by the following two >> patches: >> >> Fixes: d0c97cfb81ebc ("mmc: core: Use CMD23 for multiblock transfers when >> we can.") >> Fixes: e9d5c746246c8 ("mmc/block: switch to using blk_queue_write_cache()") >> >> I'm not sure if this is what you referred to ("Fixes tag"). Please correct me if I >> misunderstood. >> >>>> Signed-off-by: Michael Wu >>>> --- >>>> drivers/mmc/core/block.c | 20 ++++++++++++++------ >>>> 1 file changed, 14 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c >>>> index 689eb9afeeed..1e508c079c1e 100644 >>>> --- a/drivers/mmc/core/block.c >>>> +++ b/drivers/mmc/core/block.c >>>> @@ -2279,6 +2279,8 @@ static struct mmc_blk_data >> *mmc_blk_alloc_req(struct mmc_card *card, >>>> struct mmc_blk_data *md; >>>> int devidx, ret; >>>> char cap_str[10]; >>>> + bool enable_cache = false; >>>> + bool enable_fua = false; >>>> >>>> devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices, GFP_KERNEL); >>>> if (devidx < 0) { >>>> @@ -2375,12 +2377,18 @@ static struct mmc_blk_data >> *mmc_blk_alloc_req(struct mmc_card *card, >>>> md->flags |= MMC_BLK_CMD23; >>>> } >>>> >>>> - if (mmc_card_mmc(card) && >>>> - md->flags & MMC_BLK_CMD23 && >>>> - ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) || >>>> - card->ext_csd.rel_sectors)) { >>>> - md->flags |= MMC_BLK_REL_WR; >>>> - blk_queue_write_cache(md->queue.queue, true, true); >>>> + if (mmc_card_mmc(card)) { >>>> + if (md->flags & MMC_BLK_CMD23 && >>>> + ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) >> || >>>> + card->ext_csd.rel_sectors)) { >>>> + md->flags |= MMC_BLK_REL_WR; >>>> + enable_fua = true; >>>> + } >>>> + >>>> + if (mmc_cache_enabled(card->host)) >>>> + enable_cache = true; >>>> + >>>> + blk_queue_write_cache(md->queue.queue, enable_cache, >>>> + enable_fua); >>>> } >>> >>> Seems like we should inform block layer about SD card cache also >>> >> >> I saw another mail by Avri Altman, which says few days will be needed to ask >> internally. Shall I wait or make another change here on 'inform block layer >> about SD card cache'? > Please don't wait. > > Thanks, > Avri > >> >>>> >>>> string_get_size((u64)size, 512, STRING_UNITS_2, >> >> -- >> Best Regards, >> Michael Wu Hi Avril & Adrian, Thanks for your efforts. Could we have an agreement now -- 1. enabling-cache and cmd23/reliable-write should be independent; > On 14/03/2022 18:32, Adrian Hunter wrote: >> On 14/03/2022 09:26, Avri Altman wrote: >>> Hi, >>>> The mmc core enable cache on default. But it only enables cache-flushing >>>> when host supports cmd23 and eMMC supports reliable write. >>>> For hosts which do not support cmd23 or eMMCs which do not support >>>> reliable write, the cache can not be flushed by `sync` command. >>>> This may leads to cache data lost. >>>> This patch enables cache-flushing as long as cache is enabled, no >>>> matter host supports cmd23 and/or eMMC supports reliable write or >>>> not. >>> I looked in the spec and indeed couldn't find why enabling cache is >>> dependent of cmd23/reliable write. >>> Nor I was able to find the original commit log. >> >> Reliable write was added first, so it might have been an oversight: >> >> commit 881d1c25f765938a95def5afe39486ce39f9fc96 >> Author: Seungwon Jeon >> Date: Fri Oct 14 14:03:21 2011 +0900 >> >> mmc: core: Add cache control for eMMC4.5 device >> >> This patch adds cache feature of eMMC4.5 Spec. >> If device supports cache capability, host can utilize some >> specific operations. >> >> Signed-off-by: Seungwon Jeon >> Signed-off-by: Jaehoon Chung >> Signed-off-by: Chris Ball Here's what I found in the spec JESD84-B51: > 6.6.31 Cache > Caching of data shall apply only for the single block > read/write(CMD17/24), pre-defined multiple block > read/write(CMD23+CMD18/25) and open ended multiple block > read/write(CMD18/25+CMD12) commands and excludes any other access > e.g., to the register space(e.g., CMD6). Which means with CMD18/25+CMD12 (without using CMD23), the cache can also be enabled. Maybe this could be an evidence of the independence between enabling-cache and cmd23/reliable-write? 2. We don't consider supporting SD in this change. > On 14/03/2022 19:10, Avri Altman wrote: >> Here is what our SD system guys wrote: >> " In SD we don’t support reliable write and this eMMC driver may not >> be utilizing the cache feature we added in SD5.0. >> The method of cache flush is different between SD and eMMC." >> >> So adding SD seems to be out of scope of this change. Is there anything else I can do about this patch? Thanks again. -- Best Regards, Michael Wu