From faee9b05f69f22e4d65fb2c24f82eea9c6fe4062 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20S=C3=B8rensen?= Date: Sun, 2 Feb 2014 16:24:25 +0100 Subject: [PATCH] spi: omap2-mcspi: Support divide-by-n clock dividers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently a divide-by-2^n clock is used, causing a very coarse clock selection, i.e. a 10MHz device will need to use a 6MHz clock. The McSPI can also use a divide-by-n clock, this patch adds support for selecting that when possible. Signed-off-by: Stefan Sørensen Signed-off-by: Mark Brown --- drivers/spi/spi-omap2-mcspi.c | 43 +++++++++++++++++++++++++++++------ 1 file changed, 36 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c index 965539b0dbfb..8f0afdb067b8 100644 --- a/drivers/spi/spi-omap2-mcspi.c +++ b/drivers/spi/spi-omap2-mcspi.c @@ -45,6 +45,7 @@ #include #define OMAP2_MCSPI_MAX_FREQ 48000000 +#define OMAP2_MCSPI_MAX_DIVIDER 4096 #define OMAP2_MCSPI_MAX_FIFODEPTH 64 #define OMAP2_MCSPI_MAX_FIFOWCNT 0xFFFF #define SPI_AUTOSUSPEND_TIMEOUT 2000 @@ -89,6 +90,7 @@ #define OMAP2_MCSPI_CHCONF_FORCE BIT(20) #define OMAP2_MCSPI_CHCONF_FFET BIT(27) #define OMAP2_MCSPI_CHCONF_FFER BIT(28) +#define OMAP2_MCSPI_CHCONF_CLKG BIT(29) #define OMAP2_MCSPI_CHSTAT_RXS BIT(0) #define OMAP2_MCSPI_CHSTAT_TXS BIT(1) @@ -96,6 +98,7 @@ #define OMAP2_MCSPI_CHSTAT_TXFFE BIT(3) #define OMAP2_MCSPI_CHCTRL_EN BIT(0) +#define OMAP2_MCSPI_CHCTRL_EXTCLK_MASK (0xff << 8) #define OMAP2_MCSPI_WAKEUPENABLE_WKEN BIT(0) @@ -149,7 +152,7 @@ struct omap2_mcspi_cs { int word_len; struct list_head node; /* Context save and restore shadow register */ - u32 chconf0; + u32 chconf0, chctrl0; }; static inline void mcspi_write_reg(struct spi_master *master, @@ -230,10 +233,16 @@ static void omap2_mcspi_set_dma_req(const struct spi_device *spi, static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable) { + struct omap2_mcspi_cs *cs = spi->controller_state; u32 l; - l = enable ? OMAP2_MCSPI_CHCTRL_EN : 0; - mcspi_write_cs_reg(spi, OMAP2_MCSPI_CHCTRL0, l); + l = cs->chctrl0; + if (enable) + l |= OMAP2_MCSPI_CHCTRL_EN; + else + l &= ~OMAP2_MCSPI_CHCTRL_EN; + cs->chctrl0 = l; + mcspi_write_cs_reg(spi, OMAP2_MCSPI_CHCTRL0, cs->chctrl0); /* Flash post-writes */ mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHCTRL0); } @@ -840,7 +849,7 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, struct omap2_mcspi_cs *cs = spi->controller_state; struct omap2_mcspi *mcspi; struct spi_master *spi_cntrl; - u32 l = 0, div = 0; + u32 l = 0, clkd = 0, div, extclk = 0, clkg = 0; u8 word_len = spi->bits_per_word; u32 speed_hz = spi->max_speed_hz; @@ -856,7 +865,17 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, speed_hz = t->speed_hz; speed_hz = min_t(u32, speed_hz, OMAP2_MCSPI_MAX_FREQ); - div = omap2_mcspi_calc_divisor(speed_hz); + if (speed_hz < (OMAP2_MCSPI_MAX_FREQ / OMAP2_MCSPI_MAX_DIVIDER)) { + clkd = omap2_mcspi_calc_divisor(speed_hz); + speed_hz = OMAP2_MCSPI_MAX_FREQ >> clkd; + clkg = 0; + } else { + div = (OMAP2_MCSPI_MAX_FREQ + speed_hz - 1) / speed_hz; + speed_hz = OMAP2_MCSPI_MAX_FREQ / div; + clkd = (div - 1) & 0xf; + extclk = (div - 1) >> 4; + clkg = OMAP2_MCSPI_CHCONF_CLKG; + } l = mcspi_cached_chconf0(spi); @@ -885,7 +904,16 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, /* set clock divisor */ l &= ~OMAP2_MCSPI_CHCONF_CLKD_MASK; - l |= div << 2; + l |= clkd << 2; + + /* set clock granularity */ + l &= ~OMAP2_MCSPI_CHCONF_CLKG; + l |= clkg; + if (clkg) { + cs->chctrl0 &= ~OMAP2_MCSPI_CHCTRL_EXTCLK_MASK; + cs->chctrl0 |= extclk << 8; + mcspi_write_cs_reg(spi, OMAP2_MCSPI_CHCTRL0, cs->chctrl0); + } /* set SPI mode 0..3 */ if (spi->mode & SPI_CPOL) @@ -900,7 +928,7 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, mcspi_write_chconf0(spi, l); dev_dbg(&spi->dev, "setup: speed %d, sample %s edge, clk %s\n", - OMAP2_MCSPI_MAX_FREQ >> div, + speed_hz, (spi->mode & SPI_CPHA) ? "trailing" : "leading", (spi->mode & SPI_CPOL) ? "inverted" : "normal"); @@ -972,6 +1000,7 @@ static int omap2_mcspi_setup(struct spi_device *spi) cs->base = mcspi->base + spi->chip_select * 0x14; cs->phys = mcspi->phys + spi->chip_select * 0x14; cs->chconf0 = 0; + cs->chctrl0 = 0; spi->controller_state = cs; /* Link this to context save list */ list_add_tail(&cs->node, &ctx->cs);