linux-kernel - [PATCH v2 03/14] spi: spi-fsl-dspi: Reset SR flags before sending a new message

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Message-Id: <20250522-james-nxp-spi-v2-3-bea884630cfb@linaro.org>
Date: Thu, 22 May 2025 15:51:32 +0100
From: James Clark <james.clark@...aro.org>
To: Vladimir Oltean <olteanv@...il.com>, Mark Brown <broonie@...nel.org>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Matti Vaittinen <mazziesaccount@...il.com>
Cc: Conor Dooley <conor+dt@...nel.org>, Frank Li <Frank.Li@....com>, 
 Chester Lin <chester62515@...il.com>, Matthias Brugger <mbrugger@...e.com>, 
 Ghennadi Procopciuc <ghennadi.procopciuc@....nxp.com>, 
 NXP S32 Linux Team <s32@....com>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Chao Fu <B44548@...escale.com>, 
 Xiubo Li <Li.Xiubo@...escale.com>, Lukasz Majewski <lukma@...x.de>, 
 linux-spi@...r.kernel.org, imx@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 Vladimir Oltean <vladimir.oltean@....com>, 
 Dan Carpenter <dan.carpenter@...aro.org>, 
 Larisa Grigore <larisa.grigore@....com>, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH v2 03/14] spi: spi-fsl-dspi: Reset SR flags before sending
 a new message

From: Larisa Grigore <larisa.grigore@....com>

If, in a previous transfer, the controller sends more data than expected
by the DSPI target, SR.RFDF (RX FIFO is not empty) will remain asserted.
When flushing the FIFOs at the beginning of a new transfer (writing 1
into MCR.CLR_TXF and MCR.CLR_RXF), SR.RFDF should also be cleared.
Otherwise, when running in target mode with DMA, if SR.RFDF remains
asserted, the DMA callback will be fired before the controller sends any
data.

Take this opportunity to reset all Status Register fields.

Fixes: 5ce3cc567471 ("spi: spi-fsl-dspi: Provide support for DSPI slave mode operation (Vybryd vf610)")
Signed-off-by: Larisa Grigore <larisa.grigore@....com>
Signed-off-by: James Clark <james.clark@...aro.org>
---
 drivers/spi/spi-fsl-dspi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 1fa96e8189cf..863781ba6c16 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -975,6 +975,8 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr,
 				   SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF,
 				   SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF);
 
+		regmap_write(dspi->regmap, SPI_SR, SPI_SR_CLEAR);
+
 		spi_take_timestamp_pre(dspi->ctlr, dspi->cur_transfer,
 				       dspi->progress, !dspi->irq);
 

-- 
2.34.1