NULL + <small offset> != NULL, but reading from that <small offset> address
is usually not a very good idea and often leads to problems, like kernel
Oopses in this case, easily reproducible by writing to an SD-card, used in
SPI mode.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

Without this fix reloading of the driver is impossible.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

The spi_sh_msiof.c driver presently misconfigures REDG and TEDG. TEDG==0
outputs data at the **rising edge** of the clock and REDG==0 samples data
at the **falling edge** of the clock. Therefore for SPI, TEDG must be
equal to REDG, otherwise the last byte received is not sampled in SPI
mode 3.

This brings the driver in line with the SH7723 HW Reference Manual
settings documented in Figures 20.20 and 20.21 ("SPI Clock and data
timing").
Signed-off-by: NMarkus Pietrek <Markus.Pietrek@emtrion.de>
Acked-by: NMagnus Damm <damm@opensource.se>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

Update the MSIOF driver to remove the architecture
speficic spi header file and add err.h. This makes
the driver compile on non-SH architectures.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

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