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 7A3E8D2AB3C for ; Tue, 29 Oct 2024 14:08:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type: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=QWBqMCQ9m5dFkIDG+Fxd2ersqB659n0gBI8CFPt58gI=; b=Db2/oRFDhwiB8lfGjXy9GfKSeg tSrB9l7qMe5DomniRcbLKTlGz0xI41ntf4BhNpzxxo4E7+asvSLuUPt6JDvHZWxkxBFWUMHtaovlm f3xYNHZAhTvMVGkZUnEOrZywViKp2l9jok2qYW0159FHMzGTXSUpjJFoW0O96NW3zgwh7jRQD4lhh zFGWQBmor1aYsLrWjVC+nph4qqiU3XchYpR7Mirk/URi2VMCZ1yUQusqji5b3N7Q7kUuMYEJrfdEo +B4RmYev2Z+Qt67sRInCqRIenSsh+82uOlkcJbBihzJVFnWdmN7oTi7VRq1Zg81Rq0fnbgxdeAYz5 xetnAGSQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t5msy-0000000EgEK-1zuQ; Tue, 29 Oct 2024 14:07:52 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t5m9R-0000000EYeF-07kX for linux-arm-kernel@lists.infradead.org; Tue, 29 Oct 2024 13:20:51 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 68AD75C5E3E; Tue, 29 Oct 2024 13:20:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC2F1C4CECD; Tue, 29 Oct 2024 13:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730208048; bh=atIdjrSoz8cQOo8Oh3x41BjnGBTqmvpWtHpYQOqBTIY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=maPSauNb/CNnnievFOAFYOU7f38+08j7hlhokWmUHB9io3DNtx2BMgx4rZ0txddjB GO8ZTV8Myxrx2wOfS6tluq1+dap7q3kdp9o7AzxslPu8PzWJnGuO7vErF09+/TEoo1 XM23aIbOHbl66pxZKZGD46phpT/55IPOE5AbfNddUd7sWMd1Vf13R04tg2TjkwE9Yb X9nAvwaG0+niGCVERR8HS2UT9TMxZQLIL9oBm0k6cn4oKl8R0xerfhbm1u5/XPgjM2 yAhn/JrOghfLEPizGb6UQ28HL7Ssbje5uHGypz186z62YAeTi3zJocUTxeNxv8zoXe Gah5N6nGQt5jg== Date: Tue, 29 Oct 2024 13:20:43 +0000 From: Will Deacon To: huanglei Cc: catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, huanglei , arnd@arndb.de Subject: Re: Re: [PATCH] arm64/Kconfig: introduce GENERIC_ISA_DMA Message-ID: <20241029132042.GA4416@willie-the-truck> References: <20241025011641.4858-1-huanglei814@163.com> <20241028150544.GA2445@willie-the-truck> <26ed8fbb.1809.192d5ef13e5.Coremail.huanglei814@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <26ed8fbb.1809.192d5ef13e5.Coremail.huanglei814@163.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241029_062049_136318_5E97374B X-CRM114-Status: GOOD ( 24.47 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 29, 2024 at 09:41:08AM +0800, huanglei wrote: > Even if MAX_SMA_CANNELS is not defined, as long as GENETIC-SIA_DMA is > enabled， request_rma/free_rma function will also be exported, and > other modules using these two interfaces will not encounter link > errors. > > I don't know why others haven't noticed, but I discovered it when > debugging pcie parallel port drivers. And the arm/Kconfig has been > around for a long time. Please try to avoid top-posting in replies, as it makes the conversation very hard to follow. > At 2024-10-28 22:05:45, "Will Deacon" wrote: > >On Fri, Oct 25, 2024 at 09:16:41AM +0800, huanglei814 wrote: > >> From: huanglei > >> > >> Enable GENERIC_ISA_DMA feature on arm64 platform, > >> thus, request_dma and free_dma interface can be export. > >> and driver modules can use the this interfaces on arm64 > >> platform. > >> > >> Currently, many pcie parallel port drivers still use these > >> interfaces when ported to arm64 platform. > > > >Why has it taken so long for anybody to notice? > > > >> Signed-off-by: huanglei > >> --- > >> arch/arm64/Kconfig | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > >> index fd9df6dcc593..986eb251f68f 100644 > >> --- a/arch/arm64/Kconfig > >> +++ b/arch/arm64/Kconfig > >> @@ -367,6 +367,9 @@ config GENERIC_CSUM > >> config GENERIC_CALIBRATE_DELAY > >> def_bool y > >> > >> +config GENERIC_ISA_DMA > >> + def_bool y > >> + > > > > Does this actually do anything without MAX_DMA_CHANNELS defined? > > Even if MAX_SMA_CANNELS is not defined, as long as GENETIC-SIA_DMA is > enabled， request_rma/free_rma function will also be exported, and > other modules using these two interfaces will not encounter link > errors. Do the drivers do anything useful after they've linked? Can you please provide some in-tree examples of drivers that can be used on arm64 only once GENERIC_ISA_DMA is selected? If they just need some stubs for request_dma() and free_dma(), then it feels to me like that should be the default implementation, rather than having to select something to get them. Will