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Commit 6b1576aa authored by Thor Thayer's avatar Thor Thayer Committed by Mark Brown
Browse files

spi: Add Flag to Enable Slave Select with GPIO Chip Select. 



Some SPI masters require slave selection before the transfer
can begin [1]. The SPI framework currently selects the chip using
either 1) the internal CS mechanism or 2) the GPIO CS, but not both.

This patch adds a new master->flags define to indicate both the GPIO
CS and the internal chip select mechanism should be used.

Tested On:
    Altera CycloneV development kit
    Compile tested for build errors on x86_64 (allyesconfigs)

[1] DesignWare dw_apb_ssi Databook, Version 3.20a (page 39)

Signed-off-by: default avatarThor Thayer <tthayer@opensource.altera.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 2ce04684

drivers/spi/spi.c

+7 −2
Original line number Diff line number Diff line
@@ -697,10 +697,15 @@ static void spi_set_cs(struct spi_device *spi, bool enable) 
	if (spi->mode & SPI_CS_HIGH)

		enable = !enable;



	if (gpio_is_valid(spi->cs_gpio))

	if (gpio_is_valid(spi->cs_gpio)) {

		gpio_set_value(spi->cs_gpio, !enable);

	else if (spi->master->set_cs)

		/* Some SPI masters need both GPIO CS & slave_select */

		if ((spi->master->flags & SPI_MASTER_GPIO_SS) &&

		    spi->master->set_cs)

			spi->master->set_cs(spi, !enable);

	} else if (spi->master->set_cs) {

		spi->master->set_cs(spi, !enable);

	}

}



#ifdef CONFIG_HAS_DMA

include/linux/spi/spi.h

+1 −0
Original line number Diff line number Diff line
@@ -442,6 +442,7 @@ struct spi_master { 
#define SPI_MASTER_NO_TX	BIT(2)		/* can't do buffer write */

#define SPI_MASTER_MUST_RX      BIT(3)		/* requires rx */

#define SPI_MASTER_MUST_TX      BIT(4)		/* requires tx */

#define SPI_MASTER_GPIO_SS      BIT(5)		/* GPIO CS must select slave */



	/*

	 * on some hardware transfer / message size may be constrained