From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH v2 5/6] i2c: i2c-stm32f7: Add DMA support
Date: Tue, 3 Apr 2018 17:39:25 +0200
Message-ID: <20180403153925.lg37rezuvs6hefks@ninjato>
References: <1521650940-11651-1-git-send-email-pierre-yves.mordret@st.com>
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To: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>, Alexandre Torgue <alexandre.torgue@st.com>, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
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> +#define STM32F7_I2C_DMA_LEN_MIN			0x1
...

> +	if (i2c_dev->dma && f7_msg->count >= STM32F7_I2C_DMA_LEN_MIN) {

Are you using DMA for every message with a length >= 1? The setup of
that might be more expensive than the DMA gain, if so.


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