Re: [PATCH v3] dma-coherent: add support for multi coherent rmems per dev

From: Howard Yen <howardyen@google.com>
To: Christoph Hellwig <hch@lst.de>
Cc: 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
Date: Wed, 21 Feb 2024 17:27:58 +0800	[thread overview]
Message-ID: <CAJDAHvbOnAvW5f6oJUnuy2_5-vS7uJc13GQSNX_Nc25GJXSp-Q@mail.gmail.com> (raw)
In-Reply-To: <20240220055241.GA7554@lst.de>

On Tue, Feb 20, 2024 at 1:52 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Mon, Feb 19, 2024 at 07:12:18PM +0800, Howard Yen wrote:
> > I tried to upload the patch to support multiple coherent rmems per device
> > because in some system, the primary memory space for the device might
> > be limited, so that add multiple coherent rmems support per device to satisfy
> > the scenario.
>
> I'm not sure what the means.
>
> If you have non-trivial patches you really need to explain why you're
> doing in detail as you need to convince maintainers that it is useful.

Thanks for the response, let me explain more.

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.

--
Regards,

Howard