spi: SuperH MSIOF SPI Master driver V2

This patch is V2 of SPI Master support for the SuperH MSIOF.
Full duplex, spi mode 0-3, active high cs, 3-wire and lsb
first should all be supported, but the driver has so far
only been tested with "mmc_spi".

The MSIOF hardware comes with 32-bit FIFOs for receive and
transmit, and this driver simply breaks the SPI messages
into FIFO-sized chunks. The MSIOF hardware manages the pins
for clock, receive and transmit (sck/miso/mosi), but the chip
select pin is managed by software and must be configured as
a regular GPIO pin by the board code.

Performance wise there is still room for improvement, but
on a Ecovec board with the built-in sh7724 MSIOF0 this driver
gets Mini-sd read speeds of about half a megabyte per second.

Future work include better clock setup and merging of 8-bit
transfers into 32-bit words to reduce interrupt load and
improve throughput.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index c00f9e5b9df8..06e1c0c9d35e 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -223,6 +223,13 @@ config SPI_S3C24XX_GPIO
           the inbuilt hardware cannot provide the transfer mode, or
           where the board is using non hardware connected pins.
 
+config SPI_SH_MSIOF
+        tristate "SuperH MSIOF SPI controller"
+        depends on SUPERH && HAVE_CLK
+        select SPI_BITBANG
+        help
+          SPI driver for SuperH MSIOF blocks.
+
 config SPI_SH_SCI
         tristate "SuperH SCI SPI controller"
         depends on SUPERH