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 98823CF9C6B for ; Tue, 24 Sep 2024 06:39:29 +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=sYJ0/t4wg4jNXoQaUu7mh6FhTHxDgfsj8FGcrabLZVU=; b=30MV3EwzfOX1qK /DMttZJkM3AOrOT1wH/C3qodSvDDJOmCdfxOXBMkIspYi6ldPOpn7pF9rIgLErcyb925WuWVCFRB+ x5nM/nG7CgWDsbT9sXZ2+J8omJ7K1RuyAPaIts8oWura6G1kZaVLK+/iI4O6HTrHx18dHa2v3RBjz wZWLb0+R0wq2pTShbUtbAZCm43WwLIlSdfNuEBp4n2nbOMQ9V3jVkzjQxza2bE8otEqhWfOE5BYHx VDurqJoyWJWKel0+7mMbRdiiDjC5oJYqA1r+nLmAh+2GLF0eWpBFETVZaFwS6Fk93QYGzsic8mFH4 0cde9D6HzKBZZhCycBTQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1sszCk-00000001HHz-1jFP; Tue, 24 Sep 2024 06:39:22 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1sszCi-00000001HHO-2wcJ; Tue, 24 Sep 2024 06:39:20 +0000 Date: Mon, 23 Sep 2024 23:39:20 -0700 From: Christoph Hellwig To: Vladimir Kondratiev Cc: Christoph Hellwig , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH] riscv: make ZONE_DMA32 optional Message-ID: References: <20240827113611.537302-1-vladimir.kondratiev@mobileye.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Sun, Sep 22, 2024 at 10:06:59AM +0000, Vladimir Kondratiev wrote: > This is the whole point - there are platforms where you can't allocate 32-bit > dma-able memory. Ugg. They will be broke for all kinds of devices (plug in PCIe devices IP IP blocks). > Unless there's IOMMU or some platform specific tricks, > DMA address is same as physical address. Well, that's where the usual platform specific trick is, as the platforms with high DRAM either have a mapping between physical and DMA range (see the dma_ranges concept in the DMA and OF code) or a mirror of the higher addresses. Or very rarely (e.g. sparc) a required IOMMU that is always used. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv