spi: omap2-mcspi: Support divide-by-n clock dividers
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 <stefan.sorensen@spectralink.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 965539b0..8f0afdb 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -45,6 +45,7 @@
#include <linux/platform_data/spi-omap2-mcspi.h>
#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 @@
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_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 @@
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 @@
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 @@
/* 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 @@
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 @@
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);