atmel_spi: Driver for the Atmel SPI controller

This adds a driver for the SPI controller found on most AT91 and AVR32
chips, implementing the new SPI API.

Changed in v4:
  - Update to new API
  - Handle zero-length transfers appropriately. The user may send a
    zero-length SPI transfer with SPI_XFER_END set in order to
    deactivate the chip select after a series of transfers with chip
    select active. This is useful e.g. when polling the status
    register of DataFlash.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

1 files changed, 210 insertions, 0 deletions

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
new file mode 100644
index 0000000..317c0b4
--- /dev/null
+++ b/drivers/spi/atmel_spi.c
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+#include <common.h>
+#include <spi.h>
+#include <malloc.h>
+
+#include <asm/io.h>
+
+#include <asm/arch/clk.h>
+#include <asm/arch/memory-map.h>
+
+#include "atmel_spi.h"
+
+void spi_init()
+{
+
+}
+
+struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
+			unsigned int max_hz, unsigned int mode)
+{
+	struct atmel_spi_slave	*as;
+	unsigned int		scbr;
+	u32			csrx;
+	void			*regs;
+
+	if (cs > 3 || !spi_cs_is_valid(bus, cs))
+		return NULL;
+
+	switch (bus) {
+	case 0:
+		regs = (void *)SPI0_BASE;
+		break;
+#ifdef SPI1_BASE
+	case 1:
+		regs = (void *)SPI1_BASE;
+		break;
+#endif
+#ifdef SPI2_BASE
+	case 2:
+		regs = (void *)SPI2_BASE;
+		break;
+#endif
+#ifdef SPI3_BASE
+	case 3:
+		regs = (void *)SPI3_BASE;
+		break;
+#endif
+	default:
+		return NULL;
+	}
+
+
+	scbr = (get_spi_clk_rate(bus) + max_hz - 1) / max_hz;
+	if (scbr > ATMEL_SPI_CSRx_SCBR_MAX)
+		/* Too low max SCK rate */
+		return NULL;
+	if (scbr < 1)
+		scbr = 1;
+
+	csrx = ATMEL_SPI_CSRx_SCBR(scbr);
+	csrx |= ATMEL_SPI_CSRx_BITS(ATMEL_SPI_BITS_8);
+	if (!(mode & SPI_CPHA))
+		csrx |= ATMEL_SPI_CSRx_NCPHA;
+	if (mode & SPI_CPOL)
+		csrx |= ATMEL_SPI_CSRx_CPOL;
+
+	as = malloc(sizeof(struct atmel_spi_slave));
+	if (!as)
+		return NULL;
+
+	as->slave.bus = bus;
+	as->slave.cs = cs;
+	as->regs = regs;
+	as->mr = ATMEL_SPI_MR_MSTR | ATMEL_SPI_MR_MODFDIS
+			| ATMEL_SPI_MR_PCS(~(1 << cs) & 0xf);
+	spi_writel(as, CSR(cs), csrx);
+
+	return &as->slave;
+}
+
+void spi_free_slave(struct spi_slave *slave)
+{
+	struct atmel_spi_slave *as = to_atmel_spi(slave);
+
+	free(as);
+}
+
+int spi_claim_bus(struct spi_slave *slave)
+{
+	struct atmel_spi_slave *as = to_atmel_spi(slave);
+
+	/* Enable the SPI hardware */
+	spi_writel(as, CR, ATMEL_SPI_CR_SPIEN);
+
+	/*
+	 * Select the slave. This should set SCK to the correct
+	 * initial state, etc.
+	 */
+	spi_writel(as, MR, as->mr);
+
+	return 0;
+}
+
+void spi_release_bus(struct spi_slave *slave)
+{
+	struct atmel_spi_slave *as = to_atmel_spi(slave);
+
+	/* Disable the SPI hardware */
+	spi_writel(as, CR, ATMEL_SPI_CR_SPIDIS);
+}
+
+int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
+		const void *dout, void *din, unsigned long flags)
+{
+	struct atmel_spi_slave *as = to_atmel_spi(slave);
+	unsigned int	len_tx;
+	unsigned int	len_rx;
+	unsigned int	len;
+	int		ret;
+	u32		status;
+	const u8	*txp = dout;
+	u8		*rxp = din;
+	u8		value;
+
+	ret = 0;
+	if (bitlen == 0)
+		/* Finish any previously submitted transfers */
+		goto out;
+
+	/*
+	 * TODO: The controller can do non-multiple-of-8 bit
+	 * transfers, but this driver currently doesn't support it.
+	 *
+	 * It's also not clear how such transfers are supposed to be
+	 * represented as a stream of bytes...this is a limitation of
+	 * the current SPI interface.
+	 */
+	if (bitlen % 8) {
+		/* Errors always terminate an ongoing transfer */
+		flags |= SPI_XFER_END;
+		goto out;
+	}
+
+	len = bitlen / 8;
+
+	/*
+	 * The controller can do automatic CS control, but it is
+	 * somewhat quirky, and it doesn't really buy us much anyway
+	 * in the context of U-Boot.
+	 */
+	if (flags & SPI_XFER_BEGIN)
+		spi_cs_activate(slave);
+
+	for (len_tx = 0, len_rx = 0; len_rx < len; ) {
+		status = spi_readl(as, SR);
+
+		if (status & ATMEL_SPI_SR_OVRES)
+			return -1;
+
+		if (len_tx < len && (status & ATMEL_SPI_SR_TDRE)) {
+			if (txp)
+				value = *txp++;
+			else
+				value = 0;
+			spi_writel(as, TDR, value);
+			len_tx++;
+		}
+		if (status & ATMEL_SPI_SR_RDRF) {
+			value = spi_readl(as, RDR);
+			if (rxp)
+				*rxp++ = value;
+			len_rx++;
+		}
+	}
+
+out:
+	if (flags & SPI_XFER_END) {
+		/*
+		 * Wait until the transfer is completely done before
+		 * we deactivate CS.
+		 */
+		do {
+			status = spi_readl(as, SR);
+		} while (!(status & ATMEL_SPI_SR_TXEMPTY));
+
+		spi_cs_deactivate(slave);
+	}
+
+	return 0;
+}