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 7A74F12B6C for ; Fri, 23 Feb 2024 06:37:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708670250; cv=none; b=a9p2e0+NvaUAHAFiBTx3Qgfr0O2kDCw1t85cg7ZZMiY8+SCyDU0IPW6pw+HrJB2dSIxQkhm6iFV5OeXlUfWricTcNdtqjegCS++SBAOhrKIxXB9qR1eSrmoNh2HKaqFw/HqFHHXjQayv1wlDJqEuGF8uY+gl/ShD5v6MufgWXps= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708670250; c=relaxed/simple; bh=G7FfstsSz/agmPlMrQQ3PDPo+7Tic3vz0ZsyZkVN+Ys=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lqf1O/+23exM0B5OwCfOQpkKIfAnMSXO+UhWrQXf7zZAzya3ZWpY6RuVBV6GPRoRb4PNUn/7ETn53RhyC7PXj2orIycYio4TJw1EjrtwDdVpEaSQSaZ4Su8T3NYa5nbUZRhBqmpGI0GMBTFjUQ7u+OsV8buZeaCVa5U3xvRkEpo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id D3FE468D07; Fri, 23 Feb 2024 07:37:23 +0100 (CET) Date: Fri, 23 Feb 2024 07:37:23 +0100 From: Christoph Hellwig To: Howard Yen Cc: Christoph Hellwig , m.szyprowski@samsung.com, robin.murphy@arm.com, gregkh@linuxfoundation.org, andriy.shevchenko@linux.intel.com, rafael@kernel.org, broonie@kernel.org, james@equiv.tech, james.clark@arm.com, masahiroy@kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev Subject: Re: [PATCH v3] dma-coherent: add support for multi coherent rmems per dev Message-ID: <20240223063723.GB11004@lst.de> References: <20240208152808.3712149-1-howardyen@google.com> <20240213055426.GA22451@lst.de> <20240220055241.GA7554@lst.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) On Wed, Feb 21, 2024 at 05:27:58PM +0800, Howard Yen wrote: > The reason why I tried to propose this patch is that in the system I'm > working on, where the driver utilizes the coherent reserved memory in > the subsystem for DMA, which has limited memory space as its primary > usage. During the execution of the driver, there is a possibility of > encountering memory depletion scenarios with the primary one. > > To address this issue, I tried to create a patch that enables the > coherent reserved memory driver to support multiple coherent reserved > memory regions per device. This modification aims to provide the > driver with the ability to search for memory from a secondary region > if the primary memory is exhausted, and so on. This all seems pretty vague. Can you point to your driver submission and explain why it can't just use a larger region instead of multiple smaller ones?