From: Jason Gunthorpe <jgg@ziepe.ca>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>,
James Clark <james.clark@linaro.org>,
Mark Brown <broonie@kernel.org>,
Vladimir Oltean <olteanv@gmail.com>,
oe-kbuild-all@lists.linux.dev,
Larisa Grigore <larisa.grigore@nxp.com>,
Frank Li <Frank.li@nxp.com>,
linux-spi@vger.kernel.org, imx@lists.linux.dev,
linux-kernel@vger.kernel.org, kernel test robot <lkp@intel.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
iommu@lists.linux.dev
Subject: Re: [PATCH] dma-mapping: Stub out dma_{alloc,free,map}_pages() API
Date: Tue, 17 Jun 2025 12:55:14 -0300 [thread overview]
Message-ID: <20250617155514.GC1376515@ziepe.ca> (raw)
In-Reply-To: <76a8c896-d7ea-4471-99a2-34b3a7ac9804@app.fastmail.com>
On Tue, Jun 17, 2025 at 10:26:51AM +0200, Arnd Bergmann wrote:
> On Tue, Jun 17, 2025, at 09:53, Arnd Bergmann wrote:
>
> > Between SH72xx/SH76xx, SUN3 and M68328, I believe the
> > supported machines are all limited to between 1MB and 32MB in
> > the maximum configuration, which is obviously extremely
> > tight.
>
> I checked the exact numbers we're talking about here: enabling
> CONFIG_HAS_DMA on rsk7269_defconfig adds 10KB of extra vmlinux
> size, which doesn't seem too bad:
>
> text data bss dec hex filename
> 3295084 1111396 112264 4518744 44f358 vmlinux-before
> 3302836 1113652 112264 4528752 451a70 vmlinux-after
Long ago I ran some numbers for an ancient PPC system:
https://lore.kernel.org/all/20121119214922.GA5636@obsidianresearch.com/
The base smallest kernel was growing .text and a stripped down initrd
at a rate of 1MB evey 6 years.
Somehow I doubt that system (with 16MB ram I think it was) would even
fit a v6.x kernel. v3.6 was already challenging.
Even back then Greg was incredulous that an embedded system would run
a 6 year newer kernel. Here we are contemplating a 20 year newer
kernel?
I think you have the right direction, we just removed !SMP support,
removing !DMA also seems logical to me.
Jason
next prev parent reply other threads:[~2025-06-17 15:55 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-13 9:28 [PATCH v2 0/5] spi: spi-fsl-dspi: Target mode improvements James Clark
2025-06-13 9:28 ` [PATCH v2 1/5] spi: spi-fsl-dspi: Clear completion counter before initiating transfer James Clark
2025-06-13 9:28 ` [PATCH v2 2/5] spi: spi-fsl-dspi: Use non-coherent memory for DMA James Clark
2025-06-15 16:31 ` kernel test robot
2025-06-16 11:17 ` [PATCH] dma-mapping: Stub out dma_{alloc,free,map}_pages() API James Clark
2025-06-16 11:21 ` James Clark
2025-06-16 11:28 ` Arnd Bergmann
2025-06-16 11:29 ` Christoph Hellwig
2025-06-16 12:06 ` Mark Brown
2025-06-16 12:08 ` Christoph Hellwig
2025-06-16 12:11 ` Mark Brown
2025-06-16 12:14 ` Christoph Hellwig
2025-06-16 13:05 ` Mark Brown
2025-06-16 13:12 ` Christoph Hellwig
2025-06-16 13:10 ` James Clark
2025-06-16 13:13 ` Christoph Hellwig
2025-06-16 13:14 ` James Clark
2025-06-16 13:15 ` James Clark
2025-06-16 13:19 ` Christoph Hellwig
2025-06-16 13:23 ` James Clark
2025-06-16 13:48 ` Arnd Bergmann
2025-06-16 18:33 ` Arnd Bergmann
2025-06-17 4:48 ` Christoph Hellwig
2025-06-17 7:53 ` Arnd Bergmann
2025-06-17 8:26 ` Arnd Bergmann
2025-06-17 15:55 ` Jason Gunthorpe [this message]
2025-06-16 11:56 ` [PATCH v2 2/5] spi: spi-fsl-dspi: Use non-coherent memory for DMA Robin Murphy
2025-06-16 13:06 ` James Clark
2025-06-13 9:28 ` [PATCH v2 3/5] spi: spi-fsl-dspi: Increase DMA buffer size James Clark
2025-06-13 9:28 ` [PATCH v2 4/5] spi: spi-fsl-dspi: Store status directly in cur_msg->status James Clark
2025-06-13 9:29 ` [PATCH v2 5/5] spi: spi-fsl-dspi: Report FIFO overflows as errors James Clark
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