From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhangfei Subject: Re: [PATCH] mmc: dw_mmc: dw_mci_get_cd check MMC_CAP_NONREMOVABLE Date: Wed, 06 May 2015 13:30:52 +0800 Message-ID: <5549A70C.5070404@linaro.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pd0-f181.google.com ([209.85.192.181]:36074 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751047AbbEFFa7 (ORCPT ); Wed, 6 May 2015 01:30:59 -0400 Received: by pdea3 with SMTP id a3so220291196pde.3 for ; Tue, 05 May 2015 22:30:58 -0700 (PDT) In-Reply-To: <554996BB.70800@samsung.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Jaehoon Chung Cc: "linux-mmc@vger.kernel.org" , Ulf Hansson 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 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 :( 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