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[79.136.29.16]) by smtp.gmail.com with ESMTPSA id y81-v6sm1508376lje.30.2019.01.25.04.24.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 04:24:30 -0800 (PST) From: Jonas Bonn To: linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Cc: Jonas Bonn , Nicolas Ferre , Mark Brown , Alexandre Belloni , Ludovic Desroches , linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 2/2] spi-atmel: support inter-word delay Date: Fri, 25 Jan 2019 13:24:25 +0100 Message-Id: <20190125122425.30676-3-jonas@norrbonn.se> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190125122425.30676-1-jonas@norrbonn.se> References: <20190125122425.30676-1-jonas@norrbonn.se> MIME-Version: 1.0 Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the SPI slave requires an inter-word delay, configure the DLYBCT register accordingly. Tested on a SAMA5D2 board (derived from SAMA5D2-Xplained reference board). Signed-off-by: Jonas Bonn CC: Nicolas Ferre CC: Mark Brown CC: Alexandre Belloni CC: Ludovic Desroches CC: linux-spi@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org --- drivers/spi/spi-atmel.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c index 74fddcd3282b..24445bfbd74e 100644 --- a/drivers/spi/spi-atmel.c +++ b/drivers/spi/spi-atmel.c @@ -1209,13 +1209,21 @@ static int atmel_spi_setup(struct spi_device *spi) csr |= SPI_BIT(CSAAT); /* DLYBS is mostly irrelevant since we manage chipselect using GPIOs. - * - * DLYBCT would add delays between words, slowing down transfers. - * It could potentially be useful to cope with DMA bottlenecks, but - * in those cases it's probably best to just use a lower bitrate. */ csr |= SPI_BF(DLYBS, 0); - csr |= SPI_BF(DLYBCT, 0); + + /* DLYBCT adds delays between words. This is useful for slow devices + * that need a bit of time to setup the next transfer. + */ + if (spi->word_delay) { + csr |= SPI_BF(DLYBCT, + clamp_t(u8, + (as->spi_clk/1000000*spi->word_delay)>>5, + 1, 255)); + } else { + csr |= SPI_BF(DLYBCT, 0); + } + /* chipselect must have been muxed as GPIO (e.g. in board setup) */ npcs_pin = (unsigned long)spi->controller_data;