spi: davinci: add additional comments

Add comments describing the platform data members
and per-chip-select SPI configuration structure.

Also, add some comments describing the what happens
during the driver probe.

Signed-off-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Tested-By: Michael Williamson <michael.williamson@criticallink.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/arm/mach-davinci/include/mach/spi.h b/arch/arm/mach-davinci/include/mach/spi.h
index 1f8b7866bea3..38f4da5ca135 100644
--- a/arch/arm/mach-davinci/include/mach/spi.h
+++ b/arch/arm/mach-davinci/include/mach/spi.h
@@ -26,6 +26,20 @@ enum {
         SPI_VERSION_2, /* For DA8xx */
 };
 
+/**
+ * davinci_spi_platform_data - Platform data for SPI master device on DaVinci
+ *
+ * @version:    version of the SPI IP. Different DaVinci devices have slightly
+ *              varying versions of the same IP.
+ * @num_chipselect: number of chipselects supported by this SPI master
+ * @intr_line:  interrupt line used to connect the SPI IP to the ARM interrupt
+ *              controller withn the SoC. Possible values are 0 and 1.
+ * @chip_sel:   list of GPIOs which can act as chip-selects for the SPI.
+ *              SPI_INTERN_CS denotes internal SPI chip-select. Not necessary
+ *              to populate if all chip-selects are internal.
+ * @cshold_bug: set this to true if the SPI controller on your chip requires
+ *              a write to CSHOLD bit in between transfers (like in DM355).
+ */
 struct davinci_spi_platform_data {
         u8      version;
         u8      num_chipselect;
@@ -34,6 +48,24 @@ struct davinci_spi_platform_data {
         bool    cshold_bug;
 };
 
+/**
+ * davinci_spi_config - Per-chip-select configuration for SPI slave devices
+ *
+ * @wdelay:     amount of delay between transmissions. Measured in number of
+ *              SPI module clocks.
+ * @odd_parity: polarity of parity flag at the end of transmit data stream.
+ *              0 - odd parity, 1 - even parity.
+ * @parity_enable: enable transmission of parity at end of each transmit
+ *              data stream.
+ * @io_type:    type of IO transfer. Choose between polled, interrupt and DMA.
+ * @timer_disable: disable chip-select timers (setup and hold)
+ * @c2tdelay:   chip-select setup time. Measured in number of SPI module clocks.
+ * @t2cdelay:   chip-select hold time. Measured in number of SPI module clocks.
+ * @t2edelay:   transmit data finished to SPI ENAn pin inactive time. Measured
+ *              in number of SPI clocks.
+ * @c2edelay:   chip-select active to SPI ENAn signal active time. Measured in
+ *              number of SPI clocks.
+ */
 struct davinci_spi_config {
         u8      wdelay;
         u8      odd_parity;