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[209.132.180.67]) by mx.google.com with ESMTP id g22si11813853plo.130.2019.02.12.00.07.35; Tue, 12 Feb 2019 00:07:51 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728329AbfBLIFg (ORCPT + 99 others); Tue, 12 Feb 2019 03:05:36 -0500 Received: from mga05.intel.com ([192.55.52.43]:9579 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727509AbfBLIFg (ORCPT ); Tue, 12 Feb 2019 03:05:36 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Feb 2019 00:05:34 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,361,1544515200"; d="scan'208";a="137908087" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.56]) ([10.237.72.56]) by orsmga001.jf.intel.com with ESMTP; 12 Feb 2019 00:05:29 -0800 Subject: Re: [PATCH] mmc: mmc: Fix HS setting in mmc_hs400_to_hs200() To: Chaotian Jing Cc: Ulf Hansson , Matthias Brugger , Shawn Lin , Simon Horman , Kyle Roeschley , Hongjie Fang , Harish Jenny K N , "linux-mmc@vger.kernel.org" , Linux Kernel Mailing List , Linux ARM , linux-mediatek@lists.infradead.org, srv_heupstream References: <1548921212-5219-1-git-send-email-chaotian.jing@mediatek.com> <1548985091.10251.26.camel@mhfsdcap03> <0e95e1a1-843e-38ea-c4bb-e6c48432ea7c@intel.com> <4c8a616f-f424-fd58-43c5-d6042665bc58@intel.com> <1549937058.16070.5.camel@mhfsdcap03> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: <566c0c11-be9c-73a3-d7ff-34aed3ad7db0@intel.com> Date: Tue, 12 Feb 2019 10:04:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <1549937058.16070.5.camel@mhfsdcap03> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/02/19 4:04 AM, Chaotian Jing wrote: > On Tue, 2019-02-05 at 15:42 +0200, Adrian Hunter wrote: >> On 5/02/19 3:06 PM, Ulf Hansson wrote: >>> On Mon, 4 Feb 2019 at 14:42, Adrian Hunter wrote: >>>> >>>> On 4/02/19 12:54 PM, Ulf Hansson wrote: >>>>> On Mon, 4 Feb 2019 at 10:58, Adrian Hunter wrote: >>>>>> >>>>>> On 1/02/19 10:10 AM, Ulf Hansson wrote: >>>>>>> On Fri, 1 Feb 2019 at 02:38, Chaotian Jing wrote: >>>>>>>> >>>>>>>> On Thu, 2019-01-31 at 16:58 +0100, Ulf Hansson wrote: >>>>>>>>> On Thu, 31 Jan 2019 at 08:53, Chaotian Jing wrote: >>>>>>>>>> >>>>>>>>>> mmc_hs400_to_hs200() begins with the card and host in HS400 mode. >>>>>>>>>> Therefore, any commands sent to the card should use HS400 timing. >>>>>>>>>> It is incorrect to reduce frequency to 50Mhz before sending the switch >>>>>>>>>> command, in this case, only reduce clock frequency to 50Mhz but without >>>>>>>>>> host timming change, host is still in hs400 mode but clock changed from >>>>>>>>>> 200Mhz to 50Mhz, which makes the tuning result unsuitable and cause >>>>>>>>>> the switch command gets response CRC error. >>>>>>>>> >>>>>>>>> According the eMMC spec there is no violation by decreasing the clock >>>>>>>>> frequency like this. We can use whatever value <=200MHz. >>>>>>>>> >>>>>>>>> However, perhaps in practice this becomes an issue, due to the tuning >>>>>>>>> for HS400 has been done on the "current" frequency. >>>>>>>>> >>>>>>>>> As as start, I think you need to clarify this in the changelog. >>>>>>>>> >>>>>>>> Yes, reduce clock frequency to 50Mhz is no Spec violation, but it may >>>>>>>> cause __mmc_switch() gets response CRC error, decreasing the clock but >>>>>>>> without HOST mode change, on the host side, host driver do not know >>>>>>>> what's operation the core layer want to do and can only set current bus >>>>>>>> clock to 50Mhz, without tuning parameter change, it has a chance lead to >>>>>>>> response CRC error. even lower clock frequency, but with the wrong >>>>>>>> tuning parameter setting(the setting is of hs400 tuning @200Mhz). >>>>>>> >>>>>>> Right, makes sense. >>>>>>> >>>>>>>>>> >>>>>>>>>> this patch refers to mmc_select_hs400(), make the reduce clock frequency >>>>>>>>>> after card timing change. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Chaotian Jing >>>>>>>>>> --- >>>>>>>>>> drivers/mmc/core/mmc.c | 8 ++++---- >>>>>>>>>> 1 file changed, 4 insertions(+), 4 deletions(-) >>>>>>>>>> >>>>>>>>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c >>>>>>>>>> index da892a5..21b811e 100644 >>>>>>>>>> --- a/drivers/mmc/core/mmc.c >>>>>>>>>> +++ b/drivers/mmc/core/mmc.c >>>>>>>>>> @@ -1239,10 +1239,6 @@ int mmc_hs400_to_hs200(struct mmc_card *card) >>>>>>>>>> int err; >>>>>>>>>> u8 val; >>>>>>>>>> >>>>>>>>>> - /* Reduce frequency to HS */ >>>>>>>>>> - max_dtr = card->ext_csd.hs_max_dtr; >>>>>>>>>> - mmc_set_clock(host, max_dtr); >>>>>>>>>> - >>>>>>>>> >>>>>>>>> As far as I can tell, the reason to why we change the clock frequency >>>>>>>>> *before* the call to __mmc_switch() below, is probably to try to be on >>>>>>>>> the safe side and conform to the spec. >>>>>>>>> >>>>>>>> Agree, it Must be more safe with lower clock frequency, but the >>>>>>>> precondition is to make the host side recognize current timing is not >>>>>>>> HS400 mode. it has no method to find a safe setting to ensure no >>>>>>>> response CRC error when reduce clock from 200Mhz to 50Mhz. >>>>>>>>> However, I think you have a point, as the call to __mmc_switch(), >>>>>>>>> passes the "send_status" parameter as false, no other command than the >>>>>>>>> CMD6 is sent to the card. >>>>>>>>> >>>>>>>> yes, the send status command was sent only after __mmc_switch() done. >>>>>>>>>> /* Switch HS400 to HS DDR */ >>>>>>>>>> val = EXT_CSD_TIMING_HS; >>>>>>>>>> err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING, >>>>>>>>>> @@ -1253,6 +1249,10 @@ int mmc_hs400_to_hs200(struct mmc_card *card) >>>>>>>>>> >>>>>>>>>> mmc_set_timing(host, MMC_TIMING_MMC_DDR52); >>>>>>>>>> >>>>>>>>>> + /* Reduce frequency to HS */ >>>>>>>>>> + max_dtr = card->ext_csd.hs_max_dtr; >>>>>>>>>> + mmc_set_clock(host, max_dtr); >>>>>>>>>> + >>>>>>>>> >>>>>>>>> Perhaps it's even more correct to change the clock frequency before >>>>>>>>> the call to mmc_set_timing(host, MMC_TIMING_MMC_DDR52). Otherwise you >>>>>>>>> will be using the DDR52 timing in the controller, but with a too high >>>>>>>>> frequency. >>>>>>>>> >>>>>>>> for Our host, it has no impact to change the clock before or after >>>>>>>> change timing, as the mmc_set_timing() is only for host side, not >>>>>>>> related to MMC card side and no commands sent do card before the >>>>>>>> timing/clock change completed. >>>>>>> >>>>>>> Alright. After a second thought, it actually looks more consistent >>>>>>> with mmc_select_hs400() to do it after, as what you propose in >>>>>>> $subject patch. >>>>>>> >>>>>>> So, let's keep it as is. >>>>>>> >>>>>>>>>> err = mmc_switch_status(card); >>>>>>>>>> if (err) >>>>>>>>>> goto out_err; >>>>>>>>>> -- >>>>>>>>>> 1.8.1.1.dirty >>>>>>>>>> >>>>>>>>> >>>>>>>>> Finally, it sounds like you are trying to fix a real problem, can you >>>>>>>>> please provide some more information what is happening when the >>>>>>>>> problem occurs at your side? >>>>>>>>> >>>>>>>> Yes, I got a problem with new kernel version. with >>>>>>>> commit:57da0c042f4af52614f4bd1a148155a299ae5cd8, this commit makes >>>>>>>> re-tuning every time when access RPMB partition. >>>>>>> >>>>>>> Okay, could you please add this as fixes tag for the next version of the patch. >>>>>>> > Ok, sorry for late reply due to Chinese New Year. >>>>>>>> >>>>>>>> in fact, our host tuning result of hs400 is very stable and almost never >>>>>>>> get response CRC error with clock frequency at 200Mhz. but cannot ensure >>>>>>>> this tuning result also suitable when running at HS400 mode @50Mhz. as I >>>>>>>> mentioned before, the host side does not know the reason of reduce clock >>>>>>>> frequency to 50Mhz at HS400 mode, so what's the host side can do is only >>>>>>>> reduce the bus clock to 50Mhz, even it can just only set the tuning >>>>>>>> setting to default when clock frequency lower than 50Mhz, but both card >>>>>>>> & host side are still at HS400 mode, still cannot ensure this setting is >>>>>>>> suitable. >>>>>>> >>>>>>> Right, thanks for clarifying. >>>>>>> >>>>>>> So I am expecting a new version with a fixes tag and some >>>>>>> clarification of the changelog, then I am ready to apply this to give >>>>>>> it some test. >>>>>> >>>>>> The switch from HS400 mode is done for tuning at times when CRC errors are a >>>>>> possibility e.g. after a CRC error during transfer. So if the frequency is >>>>>> not to be reduced, then some mitigation is needed for the possibility that >>>>>> the CMD6 response itself will have a CRC error. >>>>> >>>>> That's a good point! >>>>> >>>>> However, how can we know that a CMD6 command is successfully >>>>> completed, if there is CRC errors detected during the transmission? I >>>>> guess we can't!? >>>> >>>> Yes, in that case, the only option is to assume the CMD6 was successful, >>>> like in >>>> >>>> commit ef3d232245ab7a1bf361c52449e612e4c8b7c5ab >>>> Author: Adrian Hunter >>>> Date: Fri Dec 2 13:16:35 2016 +0200 >>>> >>>> mmc: mmc: Relax checking for switch errors after HS200 switch >>> >>> Well, relaxing the check for switch errors, is to me a different >>> thing. This means we are first doing the CMD6, then allowing the >>> following status command (CMD13) to have CRC errors. Actually, even >>> the spec mention this as a case to consider. I guess it's because the >>> card internally have switched to a new speed mode timing. >>> >>> Allowing CRC errors for the actual CMD6 sound more fragile to me. Of >>> course, we can always try and see what happens. >>> >>> Chaotian, can you give it a go? Somehow, change the call to >>> __mmc_switch() in mmc_hs400_to_hs200(), so the CMD6 doesn't have the >>> CRC flag set. >>> > Yes, but should we add a new argument of __mmc_switch(), like "bool > ignore_crc" ?? for now, there are too many argument of __mmc_switch(). One solution for too many arguments is to make a structure to contain them. e.g. struct mmc_switch_args { u8 set; u8 index; u8 value; unsigned int timeout_ms; unsigned char timing; bool use_busy_signal; bool send_status; bool retry_crc_err; }; int __mmc_switch(struct mmc_card *card, struct mmc_switch_args *args) >>>> >>>> If we are going to do that, then we could stick with lowering the frequency >>>> first. >>> >>> Let's see what Chaotian's test may show. >>> >>>> >>>> Also I wonder if the mediatek driver could change to fixed sampling in >>>> ->set_ios() when the frequency drops for HS400 mode? >>> >>> Well, this sounds like a generic problem so if this is a possible >>> generic solution that would be great. >>> >>> Is this what sdhci is doing already? >> >> Not at present, but some drivers seem to be adjusting their settings for >> HS400 based on the frequency e.g. sdhci_msm_hs400() > > It's hard to find a suitable setting for all cards when running at HS400 > mode @50Mhz. > >