linux-kernel - [PATCH 3/4] spi: spi-fsl-dspi: Fix continuous selection format

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Message-Id: <c1e51fc92dbcc9c31dcdcdfab3eed40d7745308a.1479384571.git.maitysanchayan@gmail.com>
Date:   Thu, 17 Nov 2016 17:46:50 +0530
From:   Sanchayan Maity <maitysanchayan@...il.com>
To:     broonie@...nel.org
Cc:     stefan@...er.ch, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        Sanchayan Maity <maitysanchayan@...il.com>
Subject: [PATCH 3/4] spi: spi-fsl-dspi: Fix continuous selection format

Current DMA implementation was not handling the continuous selection
format viz. SPI chip select would be deasserted even between sequential
serial transfers. Use the cs_change variable and correctly set or
reset the CONT bit accordingly for case where peripherals require
the chip select to be asserted between sequential transfers.

Signed-off-by: Sanchayan Maity <maitysanchayan@...il.com>
---
 drivers/spi/spi-fsl-dspi.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index aee8c88..164e2e1 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -258,9 +258,16 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 	}
 
 	val = tx_word ? *(u16 *) dspi->tx : *(u8 *) dspi->tx;
-	dspi->dma->tx_dma_buf[i] = SPI_PUSHR_TXDATA(val) |
-					SPI_PUSHR_PCS(dspi->cs) |
-					SPI_PUSHR_CTAS(0);
+	if (dspi->cs_change) {
+		dspi->dma->tx_dma_buf[i] = SPI_PUSHR_TXDATA(val) |
+						SPI_PUSHR_PCS(dspi->cs) |
+						SPI_PUSHR_CTAS(0);
+	} else {
+		dspi->dma->tx_dma_buf[i] = SPI_PUSHR_TXDATA(val) |
+						SPI_PUSHR_PCS(dspi->cs) |
+						SPI_PUSHR_CTAS(0) |
+						SPI_PUSHR_CONT;
+	}
 	dspi->tx += tx_word + 1;
 
 	dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
-- 
2.10.2