spi: Clean up SPI driver interface

1. Add new structure spi_ctrlr_buses that allows platform to define a
mapping from SPI controller to buses managed by the controller.
2. Provide weak implementations of spi_init and spi_setup_slave that
will be used by platforms using the new interface.

BUG=chrome-os-partner:59832
BRANCH=None
TEST=Compiles successfully

Change-Id: Ia6f47941b786299f4d823895898ffb1b36e02f73
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/17561
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/drivers/spi/spi-generic.c

@@ -41,3 +41,38 @@ int spi_xfer(const struct spi_slave *slave, const void *dout, size_t bytesout,
 
 	return -1;
 }
+
+void __attribute__((weak)) spi_init(void)
+{
+	/* Default weak implementation - do nothing. */
+}
+
+const struct spi_ctrlr_buses spi_ctrlr_bus_map[0] __attribute__((weak));
+const size_t spi_ctrlr_bus_map_count __attribute__((weak));
+
+int __attribute__((weak)) spi_setup_slave(unsigned int bus, unsigned int cs,
+					  struct spi_slave *slave)
+{
+	size_t i;
+
+	memset(slave, 0, sizeof(*slave));
+
+	for (i = 0; i < spi_ctrlr_bus_map_count; i++) {
+		if ((spi_ctrlr_bus_map[i].bus_start <= bus) &&
+		    (spi_ctrlr_bus_map[i].bus_end >= bus)) {
+			slave->ctrlr = spi_ctrlr_bus_map[i].ctrlr;
+			break;
+		}
+	}
+
+	if (slave->ctrlr == NULL)
+		return -1;
+
+	slave->bus = bus;
+	slave->cs = cs;
+
+	if (slave->ctrlr->setup)
+		return slave->ctrlr->setup(slave);
+
+	return 0;
+}

src/include/spi-generic.h

@@ -42,14 +42,33 @@ struct spi_slave {
  * claim_bus:	Claim SPI bus and prepare for communication.
  * release_bus: Release SPI bus.
  * xfer:	SPI transfer
+ * setup:	Setup given SPI device bus.
  */
 struct spi_ctrlr {
 	int (*claim_bus)(const struct spi_slave *slave);
 	void (*release_bus)(const struct spi_slave *slave);
 	int (*xfer)(const struct spi_slave *slave, const void *dout,
 		    size_t bytesout, void *din, size_t bytesin);
+	int (*setup)(const struct spi_slave *slave);
 };
 
+/*-----------------------------------------------------------------------
+ * Structure defining mapping of SPI buses to controller.
+ *
+ * ctrlr:	Pointer to controller structure managing the given SPI buses.
+ * bus_start:	Start bus number managed by the controller.
+ * bus_end:	End bus number manager by the controller.
+ */
+struct spi_ctrlr_buses {
+	const struct spi_ctrlr *ctrlr;
+	unsigned int bus_start;
+	unsigned int bus_end;
+};
+
+/* Mapping of SPI buses to controllers - should be defined by platform. */
+extern const struct spi_ctrlr_buses spi_ctrlr_bus_map[];
+extern const size_t spi_ctrlr_bus_map_count;
+
 /*-----------------------------------------------------------------------
  * Initialization, must be called once on start up.
  *