From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 340ABC54E64 for ; Mon, 25 Mar 2024 13:45:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=lK2BZv6KrmNPHAQelOfrq+vNynsUvoF71q1FXEOC/tU=; b=E5xvkmVHyP2uac 1NfFVqNLSD92beBHYLQv+oFxnKdlDmx59sg5LA7ApxISSu35NCnvUZZY/9VIKgudWPUseBmYSi4UD sCZUbUWQHWINNiHc98QB7V0OzetuE5yDIQvkV0DktaKkqLyU5eZ2ie7NaLoplKCN8MxfV0RXHw2Wu ER+toJv+Qpr5GOnlc0OTkf2VIkLO8L6TZwllcmlm0tVzM8x0ZZeKQDa5Nq9mSWgxsTSKqZtA3hW7U 61w20/Tudwf/JwlcAnZpICsqi+HGbzO+yvkRuH75aVaamlWxOkaxyd1wq6obqxczRZ/4HH1EhKjh6 gjrF1vFrCsOiMUet8Bhw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rokdc-000000002QX-3Nvd; Mon, 25 Mar 2024 13:45:20 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rokdZ-000000002On-2v06 for linux-arm-kernel@lists.infradead.org; Mon, 25 Mar 2024 13:45:19 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id D2031CE1885; Mon, 25 Mar 2024 13:45:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D87BC433C7; Mon, 25 Mar 2024 13:45:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711374315; bh=90Iz9iyrvW8Dl1oS3Fv68W9xqNcVjqXw7FwBwxU9Ewo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OMf5Mp3AFZOQGWZyqAgvH2/qFFGURd1eoGZRSmzifZNNO83wi2vaP8EzZGXVN5tWC hLvRWOLGv6OecYkuZ7VQp/wcauHKCv83nCgJyqPInfaifVBn5x2xPZvA1jgvrGfr5e lVqDOp/NMaYejmj6pjvGEZJwusxtfCp97fB1P0AFvovFagB0Syydpi0H1wvOMcb/rs Mmrnz6hG80YNA+nF/MwFkDvkSkcYtRd/7IACuVgVgur4r0NidOtaJDbJ4YWlQv8PBY 4IVa8nxuuVzDpxRlgt+x3mhKCnIDmXpIZv1WexIwdyR3CEU1cRiN6Vik+Tx8/kaxgW 6o+4jYxTmT+vw== Date: Mon, 25 Mar 2024 14:45:09 +0100 From: Niklas Cassel To: Siddharth Vadapalli Cc: lpieralisi@kernel.org, kw@linux.com, robh@kernel.org, bhelgaas@google.com, manivannan.sadhasivam@linaro.org, fancer.lancer@gmail.com, u.kleine-koenig@pengutronix.de, dlemoal@kernel.org, yoshihiro.shimoda.uh@renesas.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, srk@ti.com Subject: Re: [PATCH v4] PCI: keystone: Fix pci_ops for AM654x SoC Message-ID: References: <20240325053722.1955433-1-s-vadapalli@ti.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240325_064518_239842_1D28BED6 X-CRM114-Status: GOOD ( 45.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Siddharth, On Mon, Mar 25, 2024 at 05:52:28PM +0530, Siddharth Vadapalli wrote: > On Mon, Mar 25, 2024 at 12:23:05PM +0100, Niklas Cassel wrote: > > On Mon, Mar 25, 2024 at 11:07:22AM +0530, Siddharth Vadapalli wrote: > > > @@ -822,6 +788,23 @@ static int __init ks_pcie_host_init(struct dw_pcie_rp *pp) > > > if (ret < 0) > > > return ret; > > > > > > > > + if (!ks_pcie->is_am6) { > > > > Perhaps add a comment here stating WHY this is needed for v3.65a (!is_am6). > > > > From reading the old threads, it appears that v3.65a: > > -Has no support for iATUs. iATU-specific resource handling code is to be > > bypassed for v3.65 h/w. Thus v3.65a has it's own .child_ops implementation, > > so that pcie-designware-host.c does not configure the iATUs. > > -v3.65a has it's own .msi_init implementation, so that pcie-designware-host.c > > does not call dw_pcie_msi_host_init() to configure the MSI controller. > > > > While 4.90a: > > -Does have iATU support. > > -Does use the generic dw_pcie_msi_host_init(). > > > > Considering the major differences (with v3.65a being the outlier) here, > > I think it would have been a much wiser idea to have two different glue > > drivers for these two compatibles (ti,keystone-pcie and ti,am654-pcie-rc). > > > > Right now the driver is quite hard to read, most of the functions in this > > driver exist because v3.65a does not have an iATU and does not use the > > generic DWC way to handle MSIs. Additionally, you have "if (!ks_pcie->is_am6)" > > spread out all over the driver, to control quite major things, like if you > > should overload .child_ops, or if you should set up inbound translation without > > an iATU. This makes is even harder to see which code is actually used for > > am654... like the fact that it actually uses the generic way to handle MSIs... > > > > The driver for am654 would be much nicer since many of the functions in > > this driver would not be needed (and the fact that you have only implemented > > EP support for am654 and not for v3.65a). All EP related stuff would be in > > the am654 file/driver. > > You could keep the quirky stuff for v3.65a in the existing pci-keystone.c > > driver. > > > > (I guess if there is a function that is identical between the twos, you could > > have a pci-keystone-common.{c,h} that can be used by both drivers, but from > > the looks of it, they seem to share very little code. > > Thank you for reviewing the patch. I agree that two drivers will be > better considering the !ks_pcie->is_am6 present throughout the driver. > However, I hope you notice the fact that commit: > 6ab15b5e7057 PCI: dwc: keystone: Convert .scan_bus() callback to use add_bus > introduced a regression in a driver which was working prior to that > commit for AM654. While there are flaws in the driver and it needs to be > split to handle v3.65a and other versions in a cleaner manner, I am > unable to understand why that is a precursor to fixing the regression. > > If splitting the driver is the only way to fix this regression, please > let me know and I will work on that instead, though it will take up more > time. I think you are misunderstanding me. I think this patch is fine, except for the comment that I gave: "Perhaps add a comment here stating WHY this is needed for v3.65a (!is_am6)." Like: /* * This is only needed for !am654 since it has its own msi_irq_chip * implementation. (am654 uses the generic msi_irq_chip implementation.) */ if (!ks_pcie->is_am6) { ... } In fact, if you move this code to ks_pcie_msi_host_init(), instead of ks_pcie_host_init(), you would not need a comment (or a if (!ks_pcie->is_am6)), since ks_pcie_msi_host_init() is only executed by !am654. My suggestion to split this driver to two different drivers is just because I noticed how different they are (am654 has iATUs, uses generic msi_irq_chip implementation and has EP-mode support. !am654 has no iATUs, its own MSI implementation and no EP-mode support.) So the am654 driver would look like most other DWC glue drivers. The non-am654 driver would look mostly like it looks today, except you would remove the EP-mode support. However, this suggestion can of course be implemented sometime in the future and should not be a blocker for the patch in $subject. Kind regards, Niklas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel