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>

1 files changed, 50 insertions, 17 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) */