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Thu, 17 Nov 2022 00:47:54 -0800 (PST) Received: from [127.0.1.1] ([2a0e:41a:894f:0:7a60:27eb:954c:5ab1]) by smtp.gmail.com with ESMTPSA id s22-20020a1709067b9600b0077205dd15basm77332ejo.66.2022.11.17.00.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 00:47:54 -0800 (PST) From: Carlo Caione Date: Thu, 17 Nov 2022 09:47:41 +0100 Subject: [PATCH 3/3] spi: meson-spicc: Lower CS between bursts MIME-Version: 1.0 Message-Id: <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> In-Reply-To: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> To: Kamlesh Gurudasani , Mark Brown , Neil Armstrong , Jerome Brunet , David Airlie , Martin Blumenstingl , Kevin Hilman , Daniel Vetter Cc: linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org, Carlo Caione X-Mailer: b4 0.10.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221117_004758_699568_330D7A00 X-CRM114-Status: GOOD ( 12.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On some hardware (reproduced on S905X) when a large payload is transmitted over SPI in bursts at the end of each burst, the clock line briefly fluctuates creating spurious clock transitions that are being recognised by the connected device as a genuine pulses, creating an offset in the data being transmitted. Lower the GPIO CS between bursts to avoid the clock being interpreted as valid. Signed-off-by: Carlo Caione --- drivers/spi/spi-meson-spicc.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/spi/spi-meson-spicc.c b/drivers/spi/spi-meson-spicc.c index d47f2623a60f..af8d74b53519 100644 --- a/drivers/spi/spi-meson-spicc.c +++ b/drivers/spi/spi-meson-spicc.c @@ -291,6 +291,10 @@ static inline void meson_spicc_setup_burst(struct meson_spicc_device *spicc) static irqreturn_t meson_spicc_irq(int irq, void *data) { struct meson_spicc_device *spicc = (void *) data; + struct spi_device *spi_dev; + + spi_dev = spicc->message->spi; + gpiod_set_value(spi_dev->cs_gpiod, 0); writel_bits_relaxed(SPICC_TC, SPICC_TC, spicc->base + SPICC_STATREG); @@ -309,6 +313,8 @@ static irqreturn_t meson_spicc_irq(int irq, void *data) /* Setup burst */ meson_spicc_setup_burst(spicc); + gpiod_set_value(spi_dev->cs_gpiod, 1); + /* Start burst */ writel_bits_relaxed(SPICC_XCH, SPICC_XCH, spicc->base + SPICC_CONREG);