From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH v2 4/4] scsi: ufs: probe and init of variant driver from the platform device Date: Mon, 8 Jun 2015 10:02:56 -0500 Message-ID: References: <1433324255-27510-1-git-send-email-ygardi@codeaurora.org> <1433324255-27510-5-git-send-email-ygardi@codeaurora.org> <763dbc7b708b5d5b18ce0b5adcc41016.squirrel@www.codeaurora.org> <68c91f08f2be6c84055a303ca8aa3fe0.squirrel@www.codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-vn0-f52.google.com ([209.85.216.52]:32931 "EHLO mail-vn0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752223AbbFHPDS (ORCPT ); Mon, 8 Jun 2015 11:03:18 -0400 In-Reply-To: <68c91f08f2be6c84055a303ca8aa3fe0.squirrel@www.codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: ygardi@codeaurora.org Cc: Akinobu Mita , merez@qti.qualcomm.com, dovl@qti.qualcomm.com, Jej B , LKML , "linux-scsi@vger.kernel.org" , linux-arm-msm , Santosh Y , linux-scsi-owner@vger.kernel.org, Subhash Jadavani , Paul Bolle , Gilad Broner , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Vinayak Holikatti , "James E.J. Bottomley" , Dolev Raviv , Christoph Hellwig , Sujit Reddy Thumma , Raviv Shvili On Sun, Jun 7, 2015 at 10:32 AM, wrote: >> 2015-06-05 5:53 GMT+09:00 : >>>> Hi Yaniv, >>>> >>>> 2015-06-03 18:37 GMT+09:00 Yaniv Gardi : >>>>> @@ -321,7 +313,22 @@ static int ufshcd_pltfrm_probe(struct >>>>> platform_device *pdev) >>>>> goto out; >>>>> } >>>>> >>>>> - hba->vops = get_variant_ops(&pdev->dev); >>>>> + err = of_platform_populate(node, NULL, NULL, &pdev->dev); >>>>> + if (err) >>>>> + dev_err(&pdev->dev, >>>>> + "%s: of_platform_populate() failed\n", >>>>> __func__); >>>>> + >>>>> + ufs_variant_node = of_get_next_available_child(node, NULL); >>>>> + >>>>> + if (!ufs_variant_node) { >>>>> + dev_dbg(&pdev->dev, "failed to find ufs_variant_node >>>>> child\n"); >>>>> + } else { >>>>> + ufs_variant_pdev = >>>>> of_find_device_by_node(ufs_variant_node); >>>>> + >>>>> + if (ufs_variant_pdev) >>>>> + hba->vops = (struct ufs_hba_variant_ops *) >>>>> + >>>>> dev_get_drvdata(&ufs_variant_pdev->dev); >>>>> + } >>>> >>>> I have no strong objection to 'ufs_variant' sub-node. But why can't we >>>> simply add an of_device_id to ufs_of_match, like below: >>>> >>>> static const struct of_device_id ufs_of_match[] = { >>>> { .compatible = "jedec,ufs-1.1"}, >>>> #if IS_ENABLED(SCSI_UFS_QCOM) >>>> { .compatible = "qcom,ufs", .data = &ufs_hba_qcom_vops }, >>>> #neidf >>>> {}, >>>> }; >>>> >>>> and get hba->vops by get_variant_ops()? >>>> >>> >>> Hi Mita, >>> thanks for your comments. >>> >>> The whole idea, of having a sub-node which includes all variant specific >>> attributes is to separate the UFS Platform device component, from the >>> need >>> to know "qcom" or any other future variant. >>> I believe it keeps the code more modular, and clean - meaning - no >>> #ifdef's and no need to include all variant attributes inside the driver >>> DT node. >>> in that case, we simply have a DT node that is compatible to the Jdec >>> standard, and sub-node to include variant info. >>> >>> I hope you agree with this new design, since it provides a good answer >>> to every future variant that will be added, without the need to change >>> the >>> platform file. >> >> Thanks for your explanation, I agree with it. >> >> I found two problems in the current code, but both can be fixed >> relatively easily as described below: >> >> 1) If ufshcd-pltfrm driver is loaded before ufs-qcom driver, >> ufshcd_pltfrm_probe() can't find a ufs_variant device. >> >> In order to trigger re-probing ufs device when ufs-qcom driver has >> been loaded, ufshcd_pltfrm_probe() should return -EPROBE_DEFER in >> case 'ufs_variant' sub-node exists and no hba->vops found. >> >> 2) Nothing prevents ufs-qcom module from being unloaded while the >> variant_ops is referenced by ufshcd-pltfrm. >> >> It can be fixed by incrementing module refcount of ufs_variant module >> by __module_get(ufs_variant_pdev->dev.driver->owener) in >> ufshcd_pltfrm_probe(), and module_put() in ufshcd_pltfrm_remove() >> to descrement the refcount. >> > > again, Mita, your comments are very appreciated. > > 1) > If ufshcd-pltfrm driver is loaded before ufs-qcom, (what actually happens > always), then the calling to of_platform_populate() which is added, > guarantees that ufs-qcom probe will be called and finish, before > ufshcd_pltfrm probe continues. > so ufs_variant device is always there, and ready. > I think it means we are safe - since either way, we make sure ufs-qcom > probe will be called and finish before dealing with ufs_variant device in > ufshcd_pltfrm probe. This is due to the fact that you have 2 platform drivers. You should only have 1 (and 1 node). If you really think you need 2, then you should do like many other common *HCIs do and make the base UFS driver a set of library functions that drivers can use or call. Look at EHCI, AHCI, SDHCI, etc. for inspiration. Rob