From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2565FA23 for ; Sun, 16 Apr 2023 06:30:33 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 26E9067373; Sun, 16 Apr 2023 08:30:29 +0200 (CEST) Date: Sun, 16 Apr 2023 08:30:28 +0200 From: Christoph Hellwig To: Zhiqiang Hou Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com Subject: Re: [RFC PATCH] dma: coherent: respect to device 'dma-coherent' property Message-ID: <20230416063028.GA6276@lst.de> References: <20230414080307.35114-1-Zhiqiang.Hou@nxp.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230414080307.35114-1-Zhiqiang.Hou@nxp.com> User-Agent: Mutt/1.5.17 (2007-11-01) On Fri, Apr 14, 2023 at 04:03:07PM +0800, Zhiqiang Hou wrote: > From: Hou Zhiqiang > > Currently, the coherent DMA memory is always mapped as writecombine > and uncached, ignored the 'dma-coherent' property in device node, > this patch is to map the memory as writeback and cached when the > device has 'dma-coherent' property. What is the use case here? The somewhat misnamed per-device coherent memory is intended for small per-device pools of sram or such used for staging memory.