From 58f46e41c1925236a1c34873caa5d1247f846005 Mon Sep 17 00:00:00 2001 From: Trent Piepho Date: Tue, 1 Oct 2013 13:14:25 -0700 Subject: spi: spi-mxs: Always set LOCK_CS There are two bits which control the CS line in the CTRL0 register: LOCK_CS and IGNORE_CRC. The latter would be better named DEASSERT_CS in SPI mode. LOCK_CS keeps CS asserted though the entire transfer. This should always be set. The DMA code will always set it, explicitly on the first segment of the first transfer, and then implicitly on all the rest by never clearing the bit from the value read from the ctrl0 register. The PIO code will explicitly set it for the first transfer, leave it set for intermediate transfers, and then clear it for the final transfer. It should not clear it. The only reason to not set LOCK_CS would be to attempt an altered protocol where CS pulses between each word. Though don't get your hopes up if you want to do this, as the hardware doesn't appear to do this in any sane manner. It appears to be related to the hardware FIFO fill level. The code can be simplified by just setting LOCK_CS once and then not needing to deal with it at all in the PIO and DMA transfer functions. Signed-off-by: Trent Piepho Cc: Marek Vasut Cc: Fabio Estevam Cc: Shawn Guo Signed-off-by: Mark Brown --- drivers/spi/spi-mxs.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'drivers') diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c index de7b1141b90..e6172aedf85 100644 --- a/drivers/spi/spi-mxs.c +++ b/drivers/spi/spi-mxs.c @@ -79,6 +79,8 @@ static int mxs_spi_setup_transfer(struct spi_device *dev, mxs_ssp_set_clk_rate(ssp, hz); + writel(BM_SSP_CTRL0_LOCK_CS, + ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET); writel(BF_SSP_CTRL1_SSP_MODE(BV_SSP_CTRL1_SSP_MODE__SPI) | BF_SSP_CTRL1_WORD_LENGTH (BV_SSP_CTRL1_WORD_LENGTH__EIGHT_BITS) | @@ -147,8 +149,6 @@ static inline void mxs_spi_enable(struct mxs_spi *spi) { struct mxs_ssp *ssp = &spi->ssp; - writel(BM_SSP_CTRL0_LOCK_CS, - ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET); writel(BM_SSP_CTRL0_IGNORE_CRC, ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR); } @@ -157,8 +157,6 @@ static inline void mxs_spi_disable(struct mxs_spi *spi) { struct mxs_ssp *ssp = &spi->ssp; - writel(BM_SSP_CTRL0_LOCK_CS, - ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR); writel(BM_SSP_CTRL0_IGNORE_CRC, ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET); } @@ -232,8 +230,6 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int cs, ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT; ctrl0 |= BM_SSP_CTRL0_DATA_XFER | mxs_spi_cs_to_reg(cs); - if (*first) - ctrl0 |= BM_SSP_CTRL0_LOCK_CS; if (!write) ctrl0 |= BM_SSP_CTRL0_READ; -- cgit v1.2.3-18-g5258