From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaehoon Chung Subject: Re: [PATCH] mmc: dw_mmc: dw_mci_get_cd check MMC_CAP_NONREMOVABLE Date: Wed, 06 May 2015 15:13:02 +0900 Message-ID: <5549B0EE.4000202@samsung.com> References: <1430816089-8857-1-git-send-email-zhangfei.gao@linaro.org> <55496227.9000904@samsung.com> <55496DC8.8060208@samsung.com> <55496F78.3080700@linaro.org> <554970B6.6020309@samsung.com> <5549796A.5090703@linaro.org> <554996BB.70800@samsung.com> <5549A70C.5070404@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mailout4.samsung.com ([203.254.224.34]:40789 "EHLO mailout4.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752199AbbEFGNI (ORCPT ); Wed, 6 May 2015 02:13:08 -0400 Received: from epcpsbgr4.samsung.com (u144.gpu120.samsung.co.kr [203.254.230.144]) by mailout4.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NNW00DHXZXQAJA0@mailout4.samsung.com> for linux-mmc@vger.kernel.org; Wed, 06 May 2015 15:13:02 +0900 (KST) In-reply-to: <5549A70C.5070404@linaro.org> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: zhangfei Cc: "linux-mmc@vger.kernel.org" , Ulf Hansson On 05/06/2015 02:30 PM, zhangfei wrote: > > > On 05/06/2015 12:21 PM, Jaehoon Chung wrote: >> Hi, Zhangfei. >> >> On 05/06/2015 11:16 AM, zhangfei wrote: >>> >>> >>> On 05/06/2015 09:39 AM, Jaehoon Chung wrote: >>>> Hi, >>>> >>>> On 05/06/2015 10:33 AM, zhangfei wrote: >>>>> >>>>> >>>>> On 05/06/2015 09:26 AM, Jaehoon Chung wrote: >>>>>> Hi, >>>>>> >>>>>> On 05/06/2015 10:14 AM, Zhangfei Gao wrote: >>>>>>> On 6 May 2015 at 08:36, Jaehoon Chung wrote: >>>>>>>> Hi, Zhangfei. >>>>>>>> >>>>>>>> If you want to check it, use the "broken-cd" and "non-removable" properties into dt-file. >>>>>>>> Did you use them? >>>>>>> >>>>>>> Yes. >>>>>>> "broken-cd" can work, but mmc_rescan keeps running. >>>>>>> "non-removable" does NOT work, which should be used for emmc. >>>>>>> Since dw_mci_get_cd only checks DW_MCI_QUIRK_BROKEN_CARD_DETECTION, so >>>>>>> only checks "broken-cd" but not check "non-removable" >>>>>> >>>>>> Did you use the usage like the below.. >>>>>> >>>>>> dwmmc0 { >>>>>> non-removable; >>>>>> broken-cd; >>>>>> }; >>>>> >>>>> non-removable and broken-cd should be used only one. >>>> >>>> Did you check the code? >>>> If non-removable is set, broken-cd should be discarded. >>>> >>>> I think that the below usage is not "must not". >>> >>> I understand you meaning, you suggest >>>>>> dwmmc0 { >>>>>> non-removable; >>>>>> broken-cd; >>>>>> }; >>> >>> drivers/mmc/host/dw_mmc.c checks broken-cd, while mmc_of_parse checks non-removable. >>> Yes, it works. >>> >>> But is it a workaround? and a little tricky. >>> It costs me some time to find why non-removable does not work, someone else may meet the same issue. >>> It does not align with Documentation/devicetree/bindings/mmc/mmc.txt, which is the guideline to write dts. >>> And see drivers/mmc/host/sdhci.c: sdhci_do_get_cd, it also checks both. >> >> "non-removable" is assumed that card is not removed. >> it's not also correct detect scheme. Then it's also able to say the broken card detection scheme. >> (if CDETECT register can't use.) >> >> BROKEN_CARD_DETECTION quirk means that it has unreliable card detection. >> When dw-mmc host controller has unreliable card detection scheme, it could be set. >> Is this tricky? i don't think so. >> >> Though non-removable doesn't set, it has to work fine, isn't? > If non-removable is not set, broken-cd has to be set. > Or set both, but usually we may not consider this at first. > > When we first want to enable emmc, we naturally use non-removable, according to Documentation/devicetree/bindings/mmc/mmc.txt Why do you use naturally non-removable? eMMC can be removed at some SoC. (It's assumption.) Is it common approach that consider how eMMC can be detected at host controller? > Only one of the properties in this section should be supplied: > - broken-cd: There is no card detection available; polling must be used. > - cd-gpios: Specify GPIOs for card detection, see gpio binding > - non-removable: non-removable slot (like eMMC); assume always present. > > But unfortunately we find it does not work and took half day to debug, happen to find broken-cd can work, though mmc_rescan is keeps running for a while, and we treat it as workaround. > > After some time, another person find broken-cd does not make sense, and debug again about non-removable, and took another half day. > > It really happens here :( Sorry for not saving your time. Hmm..To prevent your case, it seems better that apply your patch. :) Will apply at my dw-mmc tree. Thanks! Best Regards, Jaehoon Chung > > So is it better support just using non-removable for emmc, aligning with mmc.txt. > >> And i don't think that dw-mmc controller must use it since sdhci controller used. >> (I have known that sdhci controller is using that.) >> >> Well, If Ulf thinks this is tricky, i will consider this patch. >> > > Thanks >