From mboxrd@z Thu Jan 1 00:00:00 1970 From: ygardi@codeaurora.org Subject: Re: [PATCH v2 4/4] scsi: ufs: probe and init of variant driver from the platform device Date: Sun, 7 Jun 2015 15:32:02 -0000 Message-ID: <68c91f08f2be6c84055a303ca8aa3fe0.squirrel@www.codeaurora.org> References: <1433324255-27510-1-git-send-email-ygardi@codeaurora.org> <1433324255-27510-5-git-send-email-ygardi@codeaurora.org> <763dbc7b708b5d5b18ce0b5adcc41016.squirrel@www.codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Return-path: In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org To: Akinobu Mita Cc: Yaniv Gardi , merez@qti.qualcomm.com, dovl@qti.qualcomm.com, Jej B , LKML , "linux-scsi@vger.kernel.org" , linux-arm-msm@vger.kernel.org, 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 List-Id: linux-arm-msm@vger.kernel.org > 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. 2) you are right. the fix added as you suggested. let us know your thoughts about the V3 once it's uploaded thanks