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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: Noralf Tronnes <noralf@tronnes.org> Signed-off-by: Martin Sperl <kernel@martin.sperl.org> Signed-off-by: Mark Brown <broonie@kernel.org> Cc: stable@vger.kernel.org
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parent
bc0195aad0
commit
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1 changed files with 23 additions and 5 deletions
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@ -553,13 +553,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
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spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);
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bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
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/* handle all the modes */
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/* handle all the 3-wire mode */
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if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))
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cs |= BCM2835_SPI_CS_REN;
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if (spi->mode & SPI_CPOL)
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cs |= BCM2835_SPI_CS_CPOL;
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if (spi->mode & SPI_CPHA)
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cs |= BCM2835_SPI_CS_CPHA;
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else
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cs &= ~BCM2835_SPI_CS_REN;
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/* for gpio_cs set dummy CS so that no HW-CS get changed
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* we can not run this in bcm2835_spi_set_cs, as it does
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@ -592,6 +590,25 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
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return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs);
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}
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static int bcm2835_spi_prepare_message(struct spi_master *master,
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struct spi_message *msg)
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{
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struct spi_device *spi = msg->spi;
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struct bcm2835_spi *bs = spi_master_get_devdata(master);
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u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
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cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA);
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if (spi->mode & SPI_CPOL)
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cs |= BCM2835_SPI_CS_CPOL;
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if (spi->mode & SPI_CPHA)
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cs |= BCM2835_SPI_CS_CPHA;
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bcm2835_wr(bs, BCM2835_SPI_CS, cs);
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return 0;
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}
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static void bcm2835_spi_handle_err(struct spi_master *master,
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struct spi_message *msg)
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{
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@ -739,6 +756,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
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master->set_cs = bcm2835_spi_set_cs;
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master->transfer_one = bcm2835_spi_transfer_one;
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master->handle_err = bcm2835_spi_handle_err;
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master->prepare_message = bcm2835_spi_prepare_message;
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master->dev.of_node = pdev->dev.of_node;
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bs = spi_master_get_devdata(master);
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