au1550 SPI controller driver

Here is a driver for the Alchemy au1550 PSC (Programmable Serial
Controller) in SPI master mode.

It supports dma transfers using the Alchemy descriptor based dma controller
for 4-8 bits per word SPI transfers.  For 9-24 bits per word transfers, pio
irq based mode is used to avoid setup of dma channels from scratch on each
number of bits per word change.

Tested with au1550; this may also work on other MIPS Alchemy cpus, like
au1200/au1210/au1250.  Used extensively with SD card connected via SPI;
this handles 8.1MHz SPI clock transfers using dma without any problem (the
highest SPI clock freq possible with au1550 running on 324MHz).

The driver supports sharing of SPI bus by multiple devices.  All features
of Alchemy SPI mode are supported (all SPI modes, msb/lsb first, bits per
word in 4-24 range).

As the SPI clock of the controller depends on main input clock that shall
be configured externally, platform data structure for au1550 SPI controller
driver contains mainclk_hz attribute to define the input clock rate.  From
this value, dividers of the controller for SPI clock are set up for
required frequency.

Signed-off-by: Jan Nikitenko <jan.nikitenko@gmail.com>

Whitespace and section fixups.  Remove partial workaround for platform
setup bug in dma_mask setup; it couldn't work with multiple controllers.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/asm-mips/mach-au1x00/au1550_spi.h b/include/asm-mips/mach-au1x00/au1550_spi.h
new file mode 100644
index 00000000000..c2f0466523e
--- /dev/null
+++ b/include/asm-mips/mach-au1x00/au1550_spi.h
@@ -0,0 +1,16 @@
+/*
+ * au1550_spi.h - au1550 psc spi controller driver - platform data struct
+ */
+
+#ifndef _AU1550_SPI_H_
+#define _AU1550_SPI_H_
+
+struct au1550_spi_info {
+	s16 bus_num;		/* defines which PSC and IRQ to use */
+	u32 mainclk_hz;		/* main input clock frequency of PSC */
+	u16 num_chipselect;	/* number of chipselects supported */
+	void (*activate_cs)(struct au1550_spi_info *spi, int cs, int polarity);
+	void (*deactivate_cs)(struct au1550_spi_info *spi, int cs, int polarity);
+};
+
+#endif