From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Zapolskiy Subject: Re: [PATCH] mmc: sdhci: don't limit discard timeout by data line timeout Date: Thu, 28 Nov 2013 13:48:46 +0200 Message-ID: <52972D9E.8020907@mentor.com> References: <1385046445-29711-1-git-send-email-vladimir_zapolskiy@mentor.com> <528F4242.8040408@intel.com> <528F4D06.3080400@mentor.com> <528F5663.2050800@intel.com> <528F6113.2070009@mentor.com> <528F728D.3040004@intel.com> <528F7670.9040101@mentor.com> <52946412.6060001@intel.com> <5294CD6A.9000106@mentor.com> <5295AB97.4040907@intel.com> <52960860.8090807@mleia.com> <5296ECED.9060106@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from relay1.mentorg.com ([192.94.38.131]:48744 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752306Ab3K1LtJ (ORCPT ); Thu, 28 Nov 2013 06:49:09 -0500 In-Reply-To: <5296ECED.9060106@intel.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Adrian Hunter Cc: Vladimir Zapolskiy , linux-mmc@vger.kernel.org, Ed Sutter , Chris Ball On 11/28/13 09:12, Adrian Hunter wrote: > On 27/11/13 16:57, Vladimir Zapolskiy wrote: >> On 11/27/13 10:21, Adrian Hunter wrote: >>> On 26/11/13 18:33, Vladimir Zapolskiy wrote: >>>> On 11/26/13 11:04, Adrian Hunter wrote: >>>>> On 22/11/13 17:21, Vladimir Zapolskiy wrote: >>>>>> On 22.11.2013 16:04, Adrian Hunter wrote: >>>>>>> On 22/11/13 15:50, Vladimir Zapolskiy wrote: >>>>>>>> On 22.11.2013 14:04, Adrian Hunter wrote: >>>>>>>>> On 22/11/13 14:24, Vladimir Zapolskiy wrote: >>>>>>>>>> On 22.11.2013 12:38, Adrian Hunter wrote: >>>>>>>>>>> On 21/11/13 17:07, Vladimir Zapolskiy wrote: >>>>>>>>>>>> JEDEC specification defines quite high erase timeout value for 300ms >>>>>>>>>>>> multiplied by erase group number, and SD Host Controller >>>>>>>>>>>> specification >>>>>>>>>>>> data line timeout may be much less, e.g. 2^13 / 52MHz ~ 160us. >>>>>>>>>>>> >>>>>>>>>>>>> From block layer and MMC perfromance perspective it is >>>>>>>>>>>>> desirable >>>>>>>>>>>>> that >>>>>>>>>>>> millions of erase groups are discarded at once, so there is no much >>>>>>>>>>>> sense to limit maximum erase timeout by data line timeout, if a >>>>>>>>>>>> controller handles correctly erase operation without indication of >>>>>>>>>>>> data line timeout. >>>>>>>>>>> >>>>>>>>>>> Would you explain that some more. Do you mean that: >>>>>>>>>>> a) it does not have a timeout >>>>>>>>>> >>>>>>>>>> JEDEC defines a timeout on erase/trim operations, also in >>>>>>>>>> drivers/mmc/core/core.c >>>>>>>>>> there is a reasonable enough 10 minutes limitation for discard >>>>>>>>>> operations. >>>>>>>>>> >>>>>>>>>>> b) it has a timeout which is less than the timeout specified >>>>>>>>>>> by the >>>>>>>>>>> standard but the operation nevertheless completes >>>>>>>>>> >>>>>>>>>> SDHC data line timeout is enormously less than erase group timeout, >>>>>>>>>> and >>>>>>>>>> trivial testing shows that those two timeouts are independent, >>>>>>>>>> probably >>>>>>>>>> except some particular cases of controllers not known before commits >>>>>>>>>> 58d1246db3 and e056a1b5b. >>>>>>>>>> >>>>>>>>>> According to the currently implemented logic, mmc_do_erase() >>>>>>>>>> commonly is >>>>>>>>>> instructed to discard 1-2 erase groups at maximum, however it tends >>>>>>>>>> to be >>>>>>>>>> capable to successfully discard millions of erase groups at once >>>>>>>>>> ignoring >>>>>>>>>> that SDHC data line timeout limitation. >>>>>>>>>> >>>>>>>>> >>>>>>>>> You seem to be trying to say that the SDHCI spec. says that the host >>>>>>>>> controller does not timeout erase operations or uses a different >>>>>>>>> timeout >>>>>>>>> than the one programmed in the "Timeout Control Register". Where is >>>>>>>>> that is >>>>>>>>> the SDHCI spec? >>>>>>>> >>>>>>>> According to the spec a host controller timeouts erase operations >>>>>>>> like any >>>>>>>> other R1B command. >>>>>>>> >>>>>>>> So in your opinion, should there be SDHCI_QUIRK_BROKEN_TIMEOUT_VAL >>>>>>>> instead >>>>>>>> of the new quirk? >>>>>>> >>>>>>> I don't understand how SDHCI_QUIRK_BROKEN_TIMEOUT_VAL would help. It >>>>>>> just >>>>>>> sets the timeout to maximum but max_discard_to is the maximum timeout. >>>>>> >>>>>> Here I meant to do something like: >>>>>> >>>>>> if (host->quirks& SDHCI_QUIRK_BROKEN_TIMEOUT_VAL) >>>>>> mmc->max_discard_to = 0; >>>>>> >>>>>> Again I'm not sure that this applies well to all >>>>>> SDHCI_QUIRK_BROKEN_TIMEOUT_VAL >>>>>> controllers, therefore a new quirk might be better. >>>>>> >>>>>>> As I understand it you don't want to limit the discard size, either >>>>>>> because >>>>>>> your controller does not timeout, or because you are happy that the >>>>>>> maximum >>>>>>> timeout is enough for your users and their use-cases. >>>>>>> >>>>>>> If that is the case then the original patch just needs the quirk the >>>>>>> other >>>>>>> way around. i.e. >>>>>>> >>>>>>> if (host->quirks2& SDHCI_QUIRK2_NO_DISCARD_LIMIT) >>>>>>> mmc->max_discard_to = 0; >>>>>>> else >>>>>>> mmc->max_discard_to = (1<< 27) / host->timeout_clk; >>>>>> >>>>>> This suits me fine, thanks for review, and I'll resend a change based on >>>>>> this. >>>>>> >>>>>> Also I'd like to pay your attention to (1<< 27) / host->timeout_clk >>>>>> part of >>>>>> calculation, following the spec it might be better to account the actual >>>>>> value of Data Timeout Counter, otherwise a controller may get >>>>>> unintentional >>>>>> Data Timeout Error pretty soon. Please correct me, if I'm mistaken here. >>>>> >>>>> Not sure what you mean. max_discard_to is the maximum timeout (in >>>>> milliseconds) that the host controller supports. The intent is to limit >>>>> erase operations to ones that have a timeout that is less than or equal to >>>>> that. >>>> >>>> That's clear. But it's not obvious why do you prefer (1<< 27) numerator >>>> instead >>>> of secure (1<< 13) or (1<< (13 + sdhci_readl(host, >>>> SDHCI_TIMEOUT_CONTROL))). >>> >>> The maximum value of "Data Timeout Counter Value" in "Timeout Control >>> Register" is 14 and the maximum timeout is therefore (1<< 27). >> >> So, from this perspective I assume this is a potential theoretical maximum >> timeout for a controller, which may be 16384 times more than the maximum >> guaranteed timeout before getting a DAT timeout. Why is the theoretical maximum > > Where do you get the notion of "maximum guaranteed timeout"? The timeout is > what is programmed in "Data Timeout Counter Value". And exactly this "Data Timeout Counter Value" is not used in your code to predict controller's data line timeout. >> supposed to be used in calculations of a guaranteed discard operation timeout >> instead of promised DAT timeout by a controller? > > What is "promised DAT timeout"? This is a timeout with respect to "Data Timeout Counter Value". According to your words max_discard_to is the maximum timeout that the host controller supports, but such a parameter is useless, because nobody sets the host controller SDHCI_TIMEOUT_CONTROL register to maximum supported value, so there is a probability that you greatly overestimate Data Timeout value, and therefore block layer or other subsystem can't rely on it. Please correct me here. >> >>>> >>>>> Currently, the limit gets applied by the block layer before the mmc >>>>> layer is >>>>> involved so there is no possibility to take the actual timeout into >>>>> account. >>>>> However if you have erase_group_def set, then it won't make any >>>>> difference >>>>> i.e. the limit will be the same. >>>>> >>>>>> >>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Potentially the change may break some of the SDHCs on discard of >>>>>>>>>>>> mmc, >>>>>>>>>>>> and for backward compatibility a new quirk is introduced, which >>>>>>>>>>>> is NOT >>>>>>>>>>>> set by default. >>>>>>>>>>> >>>>>>>>>>> It sounds to me that what you want to do is not standard so the quirk >>>>>>>>>>> should >>>>>>>>>>> be the other way around. >>>>>>>>>> >>>>>>>>>> Please take a look at commits 58d1246db3 and e056a1b5b, I'd be >>>>>>>>>> glad, if >>>>>>>>>> you >>>>>>>>>> could elaborate to which "some host controllers" the quirk in my >>>>>>>>>> definition >>>>>>>>>> applies, I believe all other host controllers present at that time in >>>>>>>>>> drivers/mmc/host/* are capable to discard without introduced >>>>>>>>>> limitation. >>>>>>>>> >>>>>>>>> "some host controllers" == SDHCI i.e. to all of the ones you are >>>>>>>>> applying >>>>>>>>> the change. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Signed-off-by: Vladimir Zapolskiy >>>>>>>>>>>> Reported-by: Ed Sutter >>>>>>>>>>>> Cc: Chris Ball >>>>>>>>>>>> Cc: Adrian Hunter >>>>>>>>>>>> --- >>>>>>>>>>>> drivers/mmc/host/sdhci.c | 5 ++++- >>>>>>>>>>>> include/linux/mmc/sdhci.h | 1 + >>>>>>>>>>>> 2 files changed, 5 insertions(+), 1 deletion(-) >>>>>>>>>>>> >>>>>>>>>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c >>>>>>>>>>>> index bd8a098..b1fdddb 100644 >>>>>>>>>>>> --- a/drivers/mmc/host/sdhci.c >>>>>>>>>>>> +++ b/drivers/mmc/host/sdhci.c >>>>>>>>>>>> @@ -2930,7 +2930,10 @@ int sdhci_add_host(struct sdhci_host *host) >>>>>>>>>>>> if (host->quirks& >>>>>>>>>>>> SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK) >>>>>>>>>>>> host->timeout_clk = mmc->f_max / 1000; >>>>>>>>>>>> >>>>>>>>>>>> - mmc->max_discard_to = (1<< 27) / host->timeout_clk; >>>>>>>>>>>> + if (host->quirks2& SDHCI_QUIRK2_DATA_TIMEOUT_ON_DISCARD) >>>>>>>>>>>> + mmc->max_discard_to = (1<< 27) / host->timeout_clk; >>>>>>>>>>>> + else >>>>>>>>>>>> + mmc->max_discard_to = 0; >>>>>>>>>>>> >>>>>>>>>>>> mmc->caps |= MMC_CAP_SDIO_IRQ | MMC_CAP_ERASE | >>>>>>>>>>>> MMC_CAP_CMD23; >>>>>>>>>>>> >>>>>>>>>>>> diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h >>>>>>>>>>>> index 3e781b8..e7f6bd2 100644 >>>>>>>>>>>> --- a/include/linux/mmc/sdhci.h >>>>>>>>>>>> +++ b/include/linux/mmc/sdhci.h >>>>>>>>>>>> @@ -98,6 +98,7 @@ struct sdhci_host { >>>>>>>>>>>> #define SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON (1<<4) >>>>>>>>>>>> /* Controller has a non-standard host control register */ >>>>>>>>>>>> #define SDHCI_QUIRK2_BROKEN_HOST_CONTROL (1<<5) >>>>>>>>>>>> +#define SDHCI_QUIRK2_DATA_TIMEOUT_ON_DISCARD (1<<6) >>>>>>>>>>>> >>>>>>>>>>>> int irq; /* Device IRQ */ >>>>>>>>>>>> void __iomem *ioaddr; /* Mapped address */ >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>> >>>>>> >>>>> >>>>> -- >>>>> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in >>>>> the body of a message to majordomo@vger.kernel.org >>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >