spi/altera_spi: Add cs_change support
...
The Linux kernel says (spi.h) :
* All SPI transfers start with the relevant chipselect active. Normally
* it stays selected until after the last transfer in a message. Drivers
* can affect the chipselect signal using cs_change.
*
* (i) If the transfer isn't the last one in the message, this flag is
* used to make the chipselect briefly go inactive in the middle of the
* message. Toggling chipselect in this way may be needed to terminate
* a chip command, letting a single spi_message perform all of group of
* chip transactions together.
*
* (ii) When the transfer is the last one in the message, the chip may
* stay selected until the next transfer. On multi-device SPI busses
* with nothing blocking messages going to other devices, this is just
* a performance hint; starting a message to another device deselects
* this one. But in other cases, this can be used to ensure correctness.
* Some devices need protocol transactions to be built from a series of
* spi_message submissions, where the content of one message is
* determined by the results of previous messages and where the whole
* transaction
* ends when the chipselect goes intactive.
In other words, cs_change changes the default chipselect *behavior*.
Support of cs_change is necessary to implement the mci spi driver.
This patch also fix few things:
Passing the bus number to the brand new master device.
Disable chipselect during master->setup.
Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Franck Jullien
authored
on 24 Nov 2011
Sascha Hauer
committed
on 25 Nov 2011
