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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>
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@ -26,6 +26,20 @@ enum {
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SPI_VERSION_2, /* For DA8xx */
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};
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/**
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* davinci_spi_platform_data - Platform data for SPI master device on DaVinci
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*
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* @version: version of the SPI IP. Different DaVinci devices have slightly
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* varying versions of the same IP.
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* @num_chipselect: number of chipselects supported by this SPI master
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* @intr_line: interrupt line used to connect the SPI IP to the ARM interrupt
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* controller withn the SoC. Possible values are 0 and 1.
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* @chip_sel: list of GPIOs which can act as chip-selects for the SPI.
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* SPI_INTERN_CS denotes internal SPI chip-select. Not necessary
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* to populate if all chip-selects are internal.
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* @cshold_bug: set this to true if the SPI controller on your chip requires
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* a write to CSHOLD bit in between transfers (like in DM355).
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*/
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struct davinci_spi_platform_data {
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u8 version;
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u8 num_chipselect;
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@ -34,6 +48,24 @@ struct davinci_spi_platform_data {
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bool cshold_bug;
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};
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/**
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* davinci_spi_config - Per-chip-select configuration for SPI slave devices
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*
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* @wdelay: amount of delay between transmissions. Measured in number of
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* SPI module clocks.
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* @odd_parity: polarity of parity flag at the end of transmit data stream.
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* 0 - odd parity, 1 - even parity.
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* @parity_enable: enable transmission of parity at end of each transmit
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* data stream.
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* @io_type: type of IO transfer. Choose between polled, interrupt and DMA.
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* @timer_disable: disable chip-select timers (setup and hold)
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* @c2tdelay: chip-select setup time. Measured in number of SPI module clocks.
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* @t2cdelay: chip-select hold time. Measured in number of SPI module clocks.
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* @t2edelay: transmit data finished to SPI ENAn pin inactive time. Measured
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* in number of SPI clocks.
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* @c2edelay: chip-select active to SPI ENAn signal active time. Measured in
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* number of SPI clocks.
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*/
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struct davinci_spi_config {
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u8 wdelay;
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u8 odd_parity;
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@ -787,6 +787,13 @@ static int davinci_spi_request_dma(struct davinci_spi *davinci_spi)
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/**
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* davinci_spi_probe - probe function for SPI Master Controller
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* @pdev: platform_device structure which contains plateform specific data
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*
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* According to Linux Device Model this function will be invoked by Linux
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* with platform_device struct which contains the device specific info.
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* This function will map the SPI controller's memory, register IRQ,
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* Reset SPI controller and setting its registers to default value.
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* It will invoke spi_bitbang_start to create work queue so that client driver
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* can register transfer method to work queue.
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*/
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static int davinci_spi_probe(struct platform_device *pdev)
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{
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