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, 93 insertions, 31 deletions

diff --git a/common/soft_spi.c b/common/soft_spi.c
index e425061..c131650 100644
--- a/common/soft_spi.c
+++ b/common/soft_spi.c
@@ -29,6 +29,8 @@
 
 #if defined(CONFIG_SOFT_SPI)
 
+#include <malloc.h>
+
 /*-----------------------------------------------------------------------
  * Definitions
  */
@@ -39,6 +41,15 @@
 #define PRINTD(fmt,args...)
 #endif
 
+struct soft_spi_slave {
+	struct spi_slave slave;
+	unsigned int mode;
+};
+
+static inline struct soft_spi_slave *to_soft_spi(struct spi_slave *slave)
+{
+	return container_of(slave, struct soft_spi_slave, slave);
+}
 
 /*=====================================================================*/
 /*                         Public Functions                            */
@@ -56,6 +67,57 @@ void spi_init (void)
 #endif
 }
 
+struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
+		unsigned int max_hz, unsigned int mode)
+{
+	struct soft_spi_slave *ss;
+
+	if (!spi_cs_is_valid(bus, cs))
+		return NULL;
+
+	ss = malloc(sizeof(struct soft_spi_slave));
+	if (!ss)
+		return NULL;
+
+	ss->slave.bus = bus;
+	ss->slave.cs = cs;
+	ss->mode = mode;
+
+	/* TODO: Use max_hz to limit the SCK rate */
+
+	return &ss->slave;
+}
+
+void spi_free_slave(struct spi_slave *slave)
+{
+	struct soft_spi_slave *ss = to_soft_spi(slave);
+
+	free(ss);
+}
+
+int spi_claim_bus(struct spi_slave *slave)
+{
+#ifdef CFG_IMMR
+	volatile immap_t *immr = (immap_t *)CFG_IMMR;
+#endif
+	struct soft_spi_slave *ss = to_soft_spi(slave);
+
+	/*
+	 * Make sure the SPI clock is in idle state as defined for
+	 * this slave.
+	 */
+	if (ss->mode & SPI_CPOL)
+		SPI_SCL(1);
+	else
+		SPI_SCL(0);
+
+	return 0;
+}
+
+void spi_release_bus(struct spi_slave *slave)
+{
+	/* Nothing to do */
+}
 
 /*-----------------------------------------------------------------------
  * SPI transfer
@@ -68,50 +130,54 @@ void spi_init (void)
  * and "din" can point to the same memory location, in which case the
  * input data overwrites the output data (since both are buffered by
  * temporary variables, this is OK).
- *
- * If the chipsel() function is not NULL, it is called with a parameter
- * of '1' (chip select active) at the start of the transfer and again with
- * a parameter of '0' at the end of the transfer.
- *
- * If the chipsel() function _is_ NULL, it the responsibility of the
- * caller to make the appropriate chip select active before calling
- * spi_xfer() and making it inactive after spi_xfer() returns.
  */
-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)
 {
 #ifdef CFG_IMMR
 	volatile immap_t *immr = (immap_t *)CFG_IMMR;
 #endif
-	uchar tmpdin  = 0;
-	uchar tmpdout = 0;
-	int   j;
+	struct soft_spi_slave *ss = to_soft_spi(slave);
+	uchar		tmpdin  = 0;
+	uchar		tmpdout = 0;
+	const u8	*txd = dout;
+	u8		*rxd = din;
+	int		cpol = ss->mode & SPI_CPOL;
+	int		cpha = ss->mode & SPI_CPHA;
+	unsigned int	j;
 
-	PRINTD("spi_xfer: chipsel %08X dout %08X din %08X bitlen %d\n",
-		(int)chipsel, *(uint *)dout, *(uint *)din, bitlen);
+	PRINTD("spi_xfer: slave %u:%u dout %08X din %08X bitlen %u\n",
+		slave->bus, slave->cs, *(uint *)txd, *(uint *)rxd, bitlen);
 
-	if(chipsel != NULL) {
-		(*chipsel)(1);	/* select the target chip */
-	}
+	if (flags & SPI_XFER_BEGIN)
+		spi_cs_activate(slave);
 
 	for(j = 0; j < bitlen; j++) {
 		/*
 		 * Check if it is time to work on a new byte.
 		 */
 		if((j % 8) == 0) {
-			tmpdout = *dout++;
+			tmpdout = *txd++;
 			if(j != 0) {
-				*din++ = tmpdin;
+				*rxd++ = tmpdin;
 			}
 			tmpdin  = 0;
 		}
-		SPI_SCL(0);
+
+		if (!cpha)
+			SPI_SCL(!cpol);
 		SPI_SDA(tmpdout & 0x80);
 		SPI_DELAY;
-		SPI_SCL(1);
+		if (cpha)
+			SPI_SCL(!cpol);
+		else
+			SPI_SCL(cpol);
+		tmpdin	<<= 1;
+		tmpdin	|= SPI_READ;
+		tmpdout	<<= 1;
 		SPI_DELAY;
-		tmpdin  <<= 1;
-		tmpdin   |= SPI_READ;
-		tmpdout <<= 1;
+		if (cpha)
+			SPI_SCL(cpol);
 	}
 	/*
 	 * If the number of bits isn't a multiple of 8, shift the last
@@ -120,14 +186,10 @@ int  spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
 	 */
 	if((bitlen % 8) != 0)
 		tmpdin <<= 8 - (bitlen % 8);
-	*din++ = tmpdin;
-
-	SPI_SCL(0);		/* SPI wants the clock left low for idle */
+	*rxd++ = tmpdin;
 
-	if(chipsel != NULL) {
-		(*chipsel)(0);	/* deselect the target chip */
-
-	}
+	if (flags & SPI_XFER_END)
+		spi_cs_deactivate(slave);
 
 	return(0);
 }