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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED237CCA481 for ; Wed, 29 Jun 2022 06:25:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231799AbiF2GZt (ORCPT ); Wed, 29 Jun 2022 02:25:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229972AbiF2GZr (ORCPT ); Wed, 29 Jun 2022 02:25:47 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FD3C23BF1; Tue, 28 Jun 2022 23:25:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=hGxicrNA0Ky21SHQ+zvPyQeSEbMbEJ671RYnbrPw0JA=; b=qbFJAtMX0xKPZ1ARuRDdID37q4 owWkofTOSGtlKKGTJhARtkYpPKzHltLGhkndQA87MkODaY6KyO3cK4q808MkXZcOU40psAis3jQba hIlFNsykvnaIIUvqvKn2j1RZrQIeveQo7JYMztumkKhMbvD1zMb+mAEHnE6ESPqZza5WuXR5gF7PV n41lGSXcUPlvzAaeQHQhfM7f39UWgRCFoNb11FKul4UW/Ow1CvhldL3c1YOUP0JDldI562o45tZwg o0wAWuANXSfL/2mp0QfYSlqVUMbLFqDf0nTTu2Vp3DOLQ3j8ak5hAwUNMCSyw4o2Ir79RVMA1BFMh i++X3W8g==; Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o6R8w-009lUE-5F; Wed, 29 Jun 2022 06:25:42 +0000 Date: Tue, 28 Jun 2022 23:25:42 -0700 From: Christoph Hellwig To: Michael Schmitz Cc: Arnd Bergmann , Geert Uytterhoeven , scsi , Linux Kernel Mailing List , Arnd Bergmann , Jakub Kicinski , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Linux IOMMU , Khalid Aziz , "Maciej W . Rozycki" , Matt Wang , Miquel van Smoorenburg , Mark Salyzyn , linuxppc-dev , Linux-Arch , alpha , linux-m68k , Parisc List , Denis Efremov , Michael Ellerman , John Paul Adrian Glaubitz Subject: Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS Message-ID: References: <20220617125750.728590-1-arnd@kernel.org> <20220617125750.728590-4-arnd@kernel.org> <6ba86afe-bf9f-1aca-7af1-d0d348d75ffc@gmail.com> <9289fd82-285c-035f-5355-4d70ce4f87b0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, Jun 29, 2022 at 09:38:00AM +1200, Michael Schmitz wrote: > That's one of the 'liberties' I alluded to. The reason I left these in is > that I'm none too certain what device feature the DMA API uses to decide a > device isn't cache-coherent. The DMA API does not look at device features at all. It needs to be told so by the platform code. Once an architecture implements the hooks to support non-coherent DMA all devices are treated as non-coherent by default unless overriden by the architecture either globally (using the global dma_default_coherent variable) or per-device (using the dev->dma_coherent field, usually set by arch_setup_dma_ops). > If it's dev->coherent_dma_mask, the way I set > up the device in the a3000 driver should leave the coherent mask unchanged. > For the Zorro drivers, devices are set up to use the same storage to store > normal and coherent masks - something we most likely want to change. I need > to think about the ramifications of that. No, the coherent mask is slightly misnamed amd not actually related.