SPI API improvements

This patch gets rid of the spi_chipsel table and adds a handful of new
functions that makes the SPI layer cleaner and more flexible.

Instead of the spi_chipsel table, each board that wants to use SPI
gets to implement three hooks:
  * spi_cs_activate(): Activates the chipselect for a given slave
  * spi_cs_deactivate(): Deactivates the chipselect for a given slave
  * spi_cs_is_valid(): Determines if the given bus/chipselect
    combination can be activated.

Not all drivers may need those extra functions however. If that's the
case, the board code may just leave them out (assuming they know what
the driver needs) or rely on the linker to strip them out (assuming
--gc-sections is being used.)

To set up communication parameters for a given slave, the driver needs
to call spi_setup_slave(). This returns a pointer to an opaque
spi_slave struct which must be passed as a parameter to subsequent SPI
calls. This struct can be freed by calling spi_free_slave(), but most
driver probably don't want to do this.

Before starting one or more SPI transfers, the driver must call
spi_claim_bus() to gain exclusive access to the SPI bus and initialize
the hardware. When all transfers are done, the driver must call
spi_release_bus() to make the bus available to others, and possibly
shut down the SPI controller hardware.

spi_xfer() behaves mostly the same as before, but it now takes a
spi_slave parameter instead of a spi_chipsel function pointer. It also
got a new parameter, flags, which is used to specify chip select
behaviour. This may be extended with other flags in the future.

This patch has been build-tested on all powerpc and arm boards
involved. I have not tested NIOS since I don't have a toolchain for it
installed, so I expect some breakage there even though I've tried
fixing up everything I could find by visual inspection.

I have run-time tested this on AVR32 ATNGW100 using the atmel_spi and
DataFlash drivers posted as a follow-up. I'd like some help testing
other boards that use the existing SPI API.

But most of all, I'd like some comments on the new API. Is this stuff
usable for everyone? If not, why?

Changed in v4:
  - Build fixes for various boards, drivers and commands
  - Provide common struct spi_slave definition that can be extended by
    drivers
  - Pass a struct spi_slave * to spi_cs_activate and spi_cs_deactivate
  - Make default bus and mode build-time configurable
  - Override default SPI bus ID and mode on mx32ads and imx31_litekit.

Changed in v3:
  - Add opaque struct spi_slave for controller-specific data associated
    with a slave.
  - Add spi_claim_bus() and spi_release_bus()
  - Add spi_free_slave()
  - spi_setup() is now called spi_setup_slave() and returns a
    struct spi_slave
  - soft_spi now supports four SPI modes (CPOL|CPHA)
  - Add bus parameter to spi_setup_slave()
  - Convert the new i.MX32 SPI driver
  - Convert the new MC13783 RTC driver

Changed in v2:
  - Convert the mpc8xxx_spi driver and the mpc8349emds board to the
    new API.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Tested-by: Guennadi Liakhovetski <lg@denx.de>

4 files changed, 191 insertions, 61 deletions

diff --git a/drivers/rtc/ds1306.c b/drivers/rtc/ds1306.c
index 1c8ac7f..29854fc 100644
--- a/drivers/rtc/ds1306.c
+++ b/drivers/rtc/ds1306.c
@@ -62,13 +62,6 @@
 
 #define	RTC_USER_RAM_BASE	0x20
 
-/*
- * External table of chip select functions (see the appropriate board
- * support for the actual definition of the table).
- */
-extern spi_chipsel_type spi_chipsel[];
-extern int spi_chipsel_cnt;
-
 static unsigned int bin2bcd (unsigned int n);
 static unsigned char bcd2bin (unsigned char c);
 
@@ -305,11 +298,29 @@ void rtc_reset (void)
 static unsigned char rtc_read (unsigned char reg);
 static void rtc_write (unsigned char reg, unsigned char val);
 
+static struct spi_slave *slave;
+
 /* read clock time from DS1306 and return it in *tmp */
 int rtc_get (struct rtc_time *tmp)
 {
 	unsigned char sec, min, hour, mday, wday, mon, year;
 
+	/*
+	 * Assuming Vcc = 2.0V (lowest speed)
+	 *
+	 * REVISIT: If we add an rtc_init() function we can do this
+	 * step just once.
+	 */
+	if (!slave) {
+		slave = spi_setup_slave(0, CFG_SPI_RTC_DEVID, 600000,
+				SPI_MODE_3 | SPI_CS_HIGH);
+		if (!slave)
+			return;
+	}
+
+	if (spi_claim_bus(slave))
+		return;
+
 	sec = rtc_read (RTC_SECONDS);
 	min = rtc_read (RTC_MINUTES);
 	hour = rtc_read (RTC_HOURS);
@@ -318,6 +329,8 @@ int rtc_get (struct rtc_time *tmp)
 	mon = rtc_read (RTC_MONTH);
 	year = rtc_read (RTC_YEAR);
 
+	spi_release_bus(slave);
+
 	debug ("Get RTC year: %02x mon: %02x mday: %02x wday: %02x "
 	       "hr: %02x min: %02x sec: %02x\n",
 	       year, mon, mday, wday, hour, min, sec);
@@ -360,6 +373,17 @@ int rtc_get (struct rtc_time *tmp)
 /* set clock time from *tmp in DS1306 RTC */
 void rtc_set (struct rtc_time *tmp)
 {
+	/* Assuming Vcc = 2.0V (lowest speed) */
+	if (!slave) {
+		slave = spi_setup_slave(0, CFG_SPI_RTC_DEVID, 600000,
+				SPI_MODE_3 | SPI_CS_HIGH);
+		if (!slave)
+			return;
+	}
+
+	if (spi_claim_bus(slave))
+		return;
+
 	debug ("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 	       tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 	       tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
@@ -371,6 +395,8 @@ void rtc_set (struct rtc_time *tmp)
 	rtc_write (RTC_DATE_OF_MONTH, bin2bcd (tmp->tm_mday));
 	rtc_write (RTC_MONTH, bin2bcd (tmp->tm_mon));
 	rtc_write (RTC_YEAR, bin2bcd (tmp->tm_year - 2000));
+
+	spi_release_bus(slave);
 }
 
 /* ------------------------------------------------------------------------- */
@@ -378,6 +404,17 @@ void rtc_set (struct rtc_time *tmp)
 /* reset the DS1306 */
 void rtc_reset (void)
 {
+	/* Assuming Vcc = 2.0V (lowest speed) */
+	if (!slave) {
+		slave = spi_setup_slave(0, CFG_SPI_RTC_DEVID, 600000,
+				SPI_MODE_3 | SPI_CS_HIGH);
+		if (!slave)
+			return;
+	}
+
+	if (spi_claim_bus(slave))
+		return;
+
 	/* clear the control register */
 	rtc_write (RTC_CONTROL, 0x00);	/* 1st step: reset WP */
 	rtc_write (RTC_CONTROL, 0x00);	/* 2nd step: reset 1Hz, AIE1, AIE0 */
@@ -391,22 +428,18 @@ void rtc_reset (void)
 	rtc_write (RTC_HOURS_ALARM1, 0x00);
 	rtc_write (RTC_DAY_OF_WEEK_ALARM0, 0x00);
 	rtc_write (RTC_DAY_OF_WEEK_ALARM1, 0x00);
+
+	spi_release_bus(slave);
 }
 
 /* ------------------------------------------------------------------------- */
 
 static unsigned char rtc_read (unsigned char reg)
 {
-	unsigned char dout[2];	/* SPI Output Data Bytes */
-	unsigned char din[2];	/* SPI Input Data Bytes */
-
-	dout[0] = reg;
+	int ret;
 
-	if (spi_xfer (spi_chipsel[CFG_SPI_RTC_DEVID], 16, dout, din) != 0) {
-		return 0;
-	} else {
-		return din[1];
-	}
+	ret = spi_w8r8(slave, reg);
+	return ret < 0 ? 0 : ret;
 }
 
 /* ------------------------------------------------------------------------- */
@@ -419,7 +452,7 @@ static void rtc_write (unsigned char reg, unsigned char val)
 	dout[0] = 0x80 | reg;
 	dout[1] = val;
 
-	spi_xfer (spi_chipsel[CFG_SPI_RTC_DEVID], 16, dout, din);
+	spi_xfer (slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 }
 
 #endif /* end of code exclusion (see #ifdef CONFIG_SXNI855T above) */
diff --git a/drivers/rtc/mc13783-rtc.c b/drivers/rtc/mc13783-rtc.c
index 35b1b8b..b6e1501 100644
--- a/drivers/rtc/mc13783-rtc.c
+++ b/drivers/rtc/mc13783-rtc.c
@@ -24,34 +24,50 @@
 #include <rtc.h>
 #include <spi.h>
 
+static struct spi_slave *slave;
+
 int rtc_get(struct rtc_time *rtc)
 {
 	u32 day1, day2, time;
 	u32 reg;
 	int err, tim, i = 0;
 
-	spi_select(1, 0, SPI_MODE_2 | SPI_CS_HIGH);
+	if (!slave) {
+		/* FIXME: Verify the max SCK rate */
+		slave = spi_setup_slave(1, 0, 1000000,
+				SPI_MODE_2 | SPI_CS_HIGH);
+		if (!slave)
+			return -1;
+	}
+
+	if (spi_claim_bus(slave))
+		return -1;
 
 	do {
 		reg = 0x2c000000;
-		err = spi_xfer(0, 32, (uchar *)&reg, (uchar *)&day1);
+		err = spi_xfer(slave, 32, (uchar *)&reg, (uchar *)&day1,
+				SPI_XFER_BEGIN | SPI_XFER_END);
 
 		if (err)
 			return err;
 
 		reg = 0x28000000;
-		err = spi_xfer(0, 32, (uchar *)&reg, (uchar *)&time);
+		err = spi_xfer(slave, 32, (uchar *)&reg, (uchar *)&time,
+				SPI_XFER_BEGIN | SPI_XFER_END);
 
 		if (err)
 			return err;
 
 		reg = 0x2c000000;
-		err = spi_xfer(0, 32, (uchar *)&reg, (uchar *)&day2);
+		err = spi_xfer(slave, 32, (uchar *)&reg, (uchar *)&day2,
+				SPI_XFER_BEGIN | SPI_XFER_END);
 
 		if (err)
 			return err;
 	} while (day1 != day2 && i++ < 3);
 
+	spi_release_bus(slave);
+
 	tim = day1 * 86400 + time;
 	to_tm(tim, rtc);
 
@@ -65,16 +81,31 @@ void rtc_set(struct rtc_time *rtc)
 {
 	u32 time, day, reg;
 
+	if (!slave) {
+		/* FIXME: Verify the max SCK rate */
+		slave = spi_setup_slave(1, 0, 1000000,
+				SPI_MODE_2 | SPI_CS_HIGH);
+		if (!slave)
+			return;
+	}
+
 	time = mktime(rtc->tm_year, rtc->tm_mon, rtc->tm_mday,
 		      rtc->tm_hour, rtc->tm_min, rtc->tm_sec);
 	day = time / 86400;
 	time %= 86400;
 
+	if (spi_claim_bus(slave))
+		return;
+
 	reg = 0x2c000000 | day | 0x80000000;
-	spi_xfer(0, 32, (uchar *)&reg, (uchar *)&day);
+	spi_xfer(slave, 32, (uchar *)&reg, (uchar *)&day,
+			SPI_XFER_BEGIN | SPI_XFER_END);
 
 	reg = 0x28000000 | time | 0x80000000;
-	spi_xfer(0, 32, (uchar *)&reg, (uchar *)&time);
+	spi_xfer(slave, 32, (uchar *)&reg, (uchar *)&time,
+			SPI_XFER_BEGIN | SPI_XFER_END);
+
+	spi_release_bus(slave);
 }
 
 void rtc_reset(void)
diff --git a/drivers/spi/mpc8xxx_spi.c b/drivers/spi/mpc8xxx_spi.c
index 2fe838c..136fb50 100644
--- a/drivers/spi/mpc8xxx_spi.c
+++ b/drivers/spi/mpc8xxx_spi.c
@@ -24,6 +24,7 @@
 #include <common.h>
 #if defined(CONFIG_MPC8XXX_SPI) && defined(CONFIG_HARD_SPI)
 
+#include <malloc.h>
 #include <spi.h>
 #include <asm/mpc8xxx_spi.h>
 
@@ -37,6 +38,34 @@
 
 #define SPI_TIMEOUT	1000
 
+struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
+		unsigned int max_hz, unsigned int mode)
+{
+	struct spi_slave *slave;
+
+	if (!spi_cs_is_valid(bus, cs))
+		return NULL;
+
+	slave = malloc(sizeof(struct spi_slave));
+	if (!slave)
+		return NULL;
+
+	slave->bus = bus;
+	slave->cs = cs;
+
+	/*
+	 * TODO: Some of the code in spi_init() should probably move
+	 * here, or into spi_claim_bus() below.
+	 */
+
+	return slave;
+}
+
+void spi_free_slave(struct spi_slave *slave)
+{
+	free(slave);
+}
+
 void spi_init(void)
 {
 	volatile spi8xxx_t *spi = &((immap_t *) (CFG_IMMR))->spi;
@@ -53,7 +82,18 @@ void spi_init(void)
 	spi->com = 0;		/* LST bit doesn't do anything, so disregard */
 }
 
-int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
+int spi_claim_bus(struct spi_slave *slave)
+{
+	return 0;
+}
+
+void spi_release_bus(struct spi_slave *slave)
+{
+
+}
+
+int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
+		void *din, unsigned long flags)
 {
 	volatile spi8xxx_t *spi = &((immap_t *) (CFG_IMMR))->spi;
 	unsigned int tmpdout, tmpdin, event;
@@ -61,11 +101,11 @@ int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
 	int tm, isRead = 0;
 	unsigned char charSize = 32;
 
-	debug("spi_xfer: chipsel %08X dout %08X din %08X bitlen %d\n",
-	      (int)chipsel, *(uint *) dout, *(uint *) din, bitlen);
+	debug("spi_xfer: slave %u:%u dout %08X din %08X bitlen %u\n",
+	      slave->bus, slave->cs, *(uint *) dout, *(uint *) din, bitlen);
 
-	if (chipsel != NULL)
-		(*chipsel) (1);	/* select the target chip */
+	if (flags & SPI_XFER_BEGIN)
+		spi_cs_activate(slave);
 
 	spi->event = 0xffffffff;	/* Clear all SPI events */
 
@@ -135,8 +175,8 @@ int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
 		debug("*** spi_xfer: transfer ended. Value=%08x\n", tmpdin);
 	}
 
-	if (chipsel != NULL)
-		(*chipsel) (0);	/* deselect the target chip */
+	if (flags & SPI_XFER_END)
+		spi_cs_deactivate(slave);
 
 	return 0;
 }
diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c
index c166ec5..5957ada 100644
--- a/drivers/spi/mxc_spi.c
+++ b/drivers/spi/mxc_spi.c
@@ -19,6 +19,7 @@
  */
 
 #include <common.h>
+#include <malloc.h>
 #include <spi.h>
 #include <asm/io.h>
 
@@ -61,17 +62,18 @@ static unsigned long spi_bases[] = {
 	0x53f84000,
 };
 
-static unsigned long spi_base;
-
 #endif
 
-spi_chipsel_type spi_chipsel[] = {
-	(spi_chipsel_type)0,
-	(spi_chipsel_type)1,
-	(spi_chipsel_type)2,
-	(spi_chipsel_type)3,
+struct mxc_spi_slave {
+	struct spi_slave slave;
+	unsigned long	base;
+	u32		ctrl_reg;
 };
-int spi_chipsel_cnt = sizeof(spi_chipsel) / sizeof(spi_chipsel[0]);
+
+static inline struct mxc_spi_slave *to_mxc_spi_slave(struct spi_slave *slave)
+{
+	return container_of(slave, struct mxc_spi_slave, slave);
+}
 
 static inline u32 reg_read(unsigned long addr)
 {
@@ -83,30 +85,31 @@ static inline void reg_write(unsigned long addr, u32 val)
 	*(volatile unsigned long*)addr = val;
 }
 
-static u32 spi_xchg_single(u32 data, int bitlen)
+static u32 spi_xchg_single(struct spi_slave *slave, u32 data, int bitlen)
 {
-
-	unsigned int cfg_reg = reg_read(spi_base + MXC_CSPICTRL);
+	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
+	unsigned int cfg_reg = reg_read(mxcs->base + MXC_CSPICTRL);
 
 	if (MXC_CSPICTRL_BITCOUNT(bitlen - 1) != (cfg_reg & MXC_CSPICTRL_BITCOUNT(31))) {
 		cfg_reg = (cfg_reg & ~MXC_CSPICTRL_BITCOUNT(31)) |
 			MXC_CSPICTRL_BITCOUNT(bitlen - 1);
-		reg_write(spi_base + MXC_CSPICTRL, cfg_reg);
+		reg_write(mxcs->base + MXC_CSPICTRL, cfg_reg);
 	}
 
-	reg_write(spi_base + MXC_CSPITXDATA, data);
+	reg_write(mxcs->base + MXC_CSPITXDATA, data);
 
 	cfg_reg |= MXC_CSPICTRL_XCH;
 
-	reg_write(spi_base + MXC_CSPICTRL, cfg_reg);
+	reg_write(mxcs->base + MXC_CSPICTRL, cfg_reg);
 
-	while (reg_read(spi_base + MXC_CSPICTRL) & MXC_CSPICTRL_XCH)
+	while (reg_read(mxcs->base + MXC_CSPICTRL) & MXC_CSPICTRL_XCH)
 		;
 
-	return reg_read(spi_base + MXC_CSPIRXDATA);
+	return reg_read(mxcs->base + MXC_CSPIRXDATA);
 }
 
-int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
+int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
+		void *din, unsigned long flags)
 {
 	int n_blks = (bitlen + 31) / 32;
 	u32 *out_l, *in_l;
@@ -117,13 +120,10 @@ int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
 		return 1;
 	}
 
-	if (!spi_base)
-		spi_select(CONFIG_MXC_SPI_IFACE, (int)chipsel, SPI_MODE_2 | SPI_CS_HIGH);
-
 	for (i = 0, in_l = (u32 *)din, out_l = (u32 *)dout;
 	     i < n_blks;
 	     i++, in_l++, out_l++, bitlen -= 32)
-		*in_l = spi_xchg_single(*out_l, bitlen);
+		*in_l = spi_xchg_single(slave, *out_l, bitlen);
 
 	return 0;
 }
@@ -132,17 +132,17 @@ void spi_init(void)
 {
 }
 
-int spi_select(unsigned int bus, unsigned int dev, unsigned long mode)
+struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
+			unsigned int max_hz, unsigned int mode)
 {
 	unsigned int ctrl_reg;
+	struct mxc_spi_slave *mxcs;
 
 	if (bus >= sizeof(spi_bases) / sizeof(spi_bases[0]) ||
-	    dev > 3)
-		return 1;
-
-	spi_base = spi_bases[bus];
+	    cs > 3)
+		return NULL;
 
-	ctrl_reg = MXC_CSPICTRL_CHIPSELECT(dev) |
+	ctrl_reg = MXC_CSPICTRL_CHIPSELECT(cs) |
 		MXC_CSPICTRL_BITCOUNT(31) |
 		MXC_CSPICTRL_DATARATE(7) | /* FIXME: calculate data rate */
 		MXC_CSPICTRL_EN |
@@ -155,12 +155,38 @@ int spi_select(unsigned int bus, unsigned int dev, unsigned long mode)
 	if (mode & SPI_CS_HIGH)
 		ctrl_reg |= MXC_CSPICTRL_SSPOL;
 
-	reg_write(spi_base + MXC_CSPIRESET, 1);
+	mxcs = malloc(sizeof(struct mxc_spi_slave));
+	if (!mxcs)
+		return NULL;
+
+	mxcs->slave.bus = bus;
+	mxcs->slave.cs = cs;
+	mxcs->base = spi_bases[bus];
+	mxcs->ctrl_reg = ctrl_reg;
+
+	return &mxcs->slave;
+}
+
+void spi_free_slave(struct spi_slave *slave)
+{
+	free(slave);
+}
+
+int spi_claim_bus(struct spi_slave *slave)
+{
+	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
+
+	reg_write(mxcs->base + MXC_CSPIRESET, 1);
 	udelay(1);
-	reg_write(spi_base + MXC_CSPICTRL, ctrl_reg);
-	reg_write(spi_base + MXC_CSPIPERIOD,
+	reg_write(mxcs->base + MXC_CSPICTRL, mxcs->ctrl_reg);
+	reg_write(mxcs->base + MXC_CSPIPERIOD,
 		  MXC_CSPIPERIOD_32KHZ);
-	reg_write(spi_base + MXC_CSPIINT, 0);
+	reg_write(mxcs->base + MXC_CSPIINT, 0);
 
 	return 0;
 }
+
+void spi_release_bus(struct spi_slave *slave)
+{
+	/* TODO: Shut the controller down */
+}