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Thu, 12 Jun 2025 11:40:54 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: T7ec8a5524929d219 Date: Thu, 12 Jun 2025 17:40:33 +0200 From: "Arnd Bergmann" To: "James Clark" , "Vladimir Oltean" Cc: "Frank Li" , "Vladimir Oltean" , "Mark Brown" , linux-spi@vger.kernel.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: References: <20250609-james-nxp-spi-dma-v1-0-2b831e714be2@linaro.org> <20250609-james-nxp-spi-dma-v1-2-2b831e714be2@linaro.org> <20250611090107.t35zatn47vetnvse@skbuf> <20250612111514.rfb3gpmlilznrfxs@skbuf> Subject: Re: [PATCH 2/4] spi: spi-fsl-dspi: Use non-coherent memory for DMA Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Jun 12, 2025, at 16:14, James Clark wrote: > On 12/06/2025 12:15 pm, Vladimir Oltean wrote: > This leads me to realise a mistake in my original figures. My head was > stuck in target mode where we use DMA so I forgot to force DMA in host > mode to run the performance tests. The previous figures were all XSPI > mode and the small difference in performance could have been just down > to the layout of the code changing? > > Changing it to DMA mode gives figures that make much more sense: > > Coherent (4096 byte transfers): 6534 kbps > Non-coherent: 7347 kbps > > Coherent (16 byte transfers): 447 kbps > Non-coherent: 448 kbps Ok, good. The improvement from the patch is less than I had hoped for, but it does sound like at least it doesn't get worse for small transfers. Arnd