Commit acace73d authored by Martin Sperl's avatar Martin Sperl Committed by Mark Brown
Browse files

spi: bcm2835: set up spi-mode before asserting cs-gpio 



When using reverse polarity for clock (spi-cpol) on a device
the clock line gets altered after chip-select has been asserted
resulting in an additional clock beat, which confuses hardware.

This did not show when using native-CS, as the same register
is used to control cs as well as polarity, so the changes came
into effect at the same time. Unfortunately this is not true
with gpio-cs.

To avoid this situation this patch moves the setup of polarity
(spi-cpol and spi-cpha) outside of the chip-select into
prepare_message, which is run prior to asserting chip-select.

Also fixes resetting 3-wire mode after use of rx-mode, so that
a 3-Wire sequence TX, RX, TX works as well (right now it runs
TX, RX, RX instead)

Reported-by: default avatarNoralf Tronnes <noralf@tronnes.org>
Signed-off-by: default avatarMartin Sperl <kernel@martin.sperl.org>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
parent bc0195aa

drivers/spi/spi-bcm2835.c

+23 −5
Original line number Diff line number Diff line
@@ -553,13 +553,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, 
	spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);

	bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);



	/* handle all the modes */

	/* handle all the 3-wire mode */

	if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))

		cs |= BCM2835_SPI_CS_REN;

	if (spi->mode & SPI_CPOL)

		cs |= BCM2835_SPI_CS_CPOL;

	if (spi->mode & SPI_CPHA)

		cs |= BCM2835_SPI_CS_CPHA;

	else

		cs &= ~BCM2835_SPI_CS_REN;



	/* for gpio_cs set dummy CS so that no HW-CS get changed

	 * we can not run this in bcm2835_spi_set_cs, as it does
@@ -592,6 +590,25 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, 
	return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs);

}



static int bcm2835_spi_prepare_message(struct spi_master *master,

				       struct spi_message *msg)

{

	struct spi_device *spi = msg->spi;

	struct bcm2835_spi *bs = spi_master_get_devdata(master);

	u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);



	cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA);



	if (spi->mode & SPI_CPOL)

		cs |= BCM2835_SPI_CS_CPOL;

	if (spi->mode & SPI_CPHA)

		cs |= BCM2835_SPI_CS_CPHA;



	bcm2835_wr(bs, BCM2835_SPI_CS, cs);



	return 0;

}



static void bcm2835_spi_handle_err(struct spi_master *master,

				   struct spi_message *msg)

{
@@ -739,6 +756,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) 
	master->set_cs = bcm2835_spi_set_cs;

	master->transfer_one = bcm2835_spi_transfer_one;

	master->handle_err = bcm2835_spi_handle_err;

	master->prepare_message = bcm2835_spi_prepare_message;

	master->dev.of_node = pdev->dev.of_node;



	bs = spi_master_get_devdata(master);

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