Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935775AbdCXKuF (ORCPT ); Fri, 24 Mar 2017 06:50:05 -0400 Received: from mail-vk0-f41.google.com ([209.85.213.41]:34064 "EHLO mail-vk0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934526AbdCXKt6 (ORCPT ); Fri, 24 Mar 2017 06:49:58 -0400 MIME-Version: 1.0 In-Reply-To: <1490348427.22814.19.camel@mhfsdcap03> References: <1490336341-22292-1-git-send-email-chaotian.jing@mediatek.com> <1490336341-22292-2-git-send-email-chaotian.jing@mediatek.com> <13a83728-0031-5683-c371-4b517df32299@intel.com> <1490344369.22814.10.camel@mhfsdcap03> <03d54000-9ced-1b31-df80-d254f02433db@intel.com> <1490348427.22814.19.camel@mhfsdcap03> From: Ulf Hansson Date: Fri, 24 Mar 2017 11:49:55 +0100 Message-ID: Subject: Re: [PATCH] mmc: core: Do not hold re-tuning during CMD6 commands To: Chaotian Jing Cc: Adrian Hunter , Matthias Brugger , Jaehoon Chung , Shawn Lin , Masahiro Yamada , "linux-mmc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , linux-mediatek@lists.infradead.org, srv_heupstream Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4115 Lines: 93 On 24 March 2017 at 10:40, Chaotian Jing wrote: > On Fri, 2017-03-24 at 11:19 +0200, Adrian Hunter wrote: >> On 24/03/17 10:32, Chaotian Jing wrote: >> > On Fri, 2017-03-24 at 09:52 +0200, Adrian Hunter wrote: >> >> On 24/03/17 08:19, Chaotian Jing wrote: >> >>> this patch is refine for 'commit c6dbab9cb58f ("mmc: core: Hold re-tuning >> >>> during switch commands")' >> >>> Since it has 3 retries at max for CMD6, if the first CMD6 got CRC error, >> >>> then should do re-tune before the next CMD6 was sent. >> >>> >> >>> Signed-off-by: Chaotian Jing >> >>> --- >> >>> drivers/mmc/core/mmc_ops.c | 3 +-- >> >>> 1 file changed, 1 insertion(+), 2 deletions(-) >> >>> >> >>> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c >> >>> index fe80f26..6931927 100644 >> >>> --- a/drivers/mmc/core/mmc_ops.c >> >>> +++ b/drivers/mmc/core/mmc_ops.c >> >>> @@ -534,8 +534,6 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value, >> >>> bool use_r1b_resp = use_busy_signal; >> >>> unsigned char old_timing = host->ios.timing; >> >>> >> >>> - mmc_retune_hold(host); >> >>> - >> >>> /* >> >>> * If the cmd timeout and the max_busy_timeout of the host are both >> >>> * specified, let's validate them. A failure means we need to prevent >> >>> @@ -567,6 +565,7 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value, >> >>> cmd.sanitize_busy = true; >> >>> >> >>> err = mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES); >> >>> + mmc_retune_hold(host); >> >> >> >> That is not how mmc_retune_hold() works, you need mmc_retune_hold_now() as >> >> it is here: >> >> >> >> https://marc.info/?l=linux-mmc&m=148940903816582 >> >> >> >> But using "retries" with commands that have busy-waiting on the data line >> >> doesn't make much sense anyway. Particularly with CRC errors, I would >> >> expect the card is actually busily doing the switch and we need only to wait >> >> for it. The same can be true for timeout errors. For some CMD6 we might >> >> need to send CMD12 if the card is busy after an error. I would prefer an >> >> explicit attempt at recovery from CMD6 errors. >> >> >> > >> > It's the host driver's responsibility to ensure card is not in busy >> > state before issue the next R1B command, or the MMC core layer needs do >> > extra check/waiting before issue a R1B command. >> >> Better to deal with cards stuck in busy from the places where busy-waiting >> is expected. >> > Yes, if a R1B command got response CRC error, we can do busy-waiting in > the error hander funtion(mmc_wait_for_req_done()) That would introduce too big changes and I am sure it will cause/hide other problems. If there is a problem in __mmc_switch(), let's try to fix it there first. >> > I think the purpose of "re-tune" is trying to cover particular case(eg. >> > voltage fluctuate or EMI or some glitch of host/device which caused CRC >> > error) >> >> No, re-tuning is to compensate for drift caused primarily by temperature change. >> > Yes, by JEDEC spec, temperature change cause timing drift of EMMC > device, but, as you mentioned, maybe I have a hardware problem of host, > but needs Software to cover it. so that we are doing our best to do > re-tune if got CRC error. if could recover it, then it's better than > system hung. Exactly in what cases do you get CRC errors for CMD6. We need a full cmd log to understand and to help. >> > error) , but in such cases, too many cases are disable re-tune function >> > by mmc_retune_hold(), for example, in this case, if a response CRC error >> > got then we never have chance to recover it. then cause system cannot >> > access emmc or suspend/resume fail. >> >> Maybe you have a hardware problem. There is no way I am going to accept patches touching this part of the mmc core, without providing real evidence for how it solves a problem. To me, it seems like you are applying a workaround for another issue. Again, try to provide us with some more data and logs, then perhaps we can help narrow down the issues. Kind regards Uffe