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spi: bcm2835: Drop unused code for native Chip Select
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Commit a30a555 ("spi: bcm2835: transform native-cs to gpio-cs on
first spi_setup") disabled the use of hardware-controlled native Chip
Select in favour of software-controlled GPIO Chip Select but left code
to support the former untouched.  Remove it to simplify the driver and
ease the addition of new features and further optimizations.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
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Lukas Wunner authored and Mark Brown committed Nov 28, 2018
1 parent c06eea7 commit 5c09e42
Showing 1 changed file with 13 additions and 83 deletions.
96 changes: 13 additions & 83 deletions drivers/spi/spi-bcm2835.c
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Original file line number Diff line number Diff line change
Expand Up @@ -172,28 +172,16 @@ static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
{
struct bcm2835_spi *bs = spi_master_get_devdata(master);

/* fill in fifo if we have gpio-cs
* note that there have been rare events where the native-CS
* flapped for <1us which may change the behaviour
* with gpio-cs this does not happen, so it is implemented
* only for this case
*/
if (gpio_is_valid(spi->cs_gpio)) {
/* enable HW block, but without interrupts enabled
* this would triggern an immediate interrupt
*/
bcm2835_wr(bs, BCM2835_SPI_CS,
cs | BCM2835_SPI_CS_TA);
/* fill in tx fifo as much as possible */
bcm2835_wr_fifo(bs);
}

/*
* Enable the HW block. This will immediately trigger a DONE (TX
* empty) interrupt, upon which we will fill the TX FIFO with the
* first TX bytes. Pre-filling the TX FIFO here to avoid the
* interrupt doesn't work:-(
* Enable HW block, but with interrupts still disabled.
* Otherwise the empty TX FIFO would immediately trigger an interrupt.
*/
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);

/* fill TX FIFO as much as possible */
bcm2835_wr_fifo(bs);

/* enable interrupts */
cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;
bcm2835_wr(bs, BCM2835_SPI_CS, cs);

Expand Down Expand Up @@ -356,10 +344,6 @@ static bool bcm2835_spi_can_dma(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
{
/* only run for gpio_cs */
if (!gpio_is_valid(spi->cs_gpio))
return false;

/* we start DMA efforts only on bigger transfers */
if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
return false;
Expand Down Expand Up @@ -559,12 +543,12 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
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
* not get called for cs_gpio cases, so we need to do it here
/*
* The driver always uses software-controlled GPIO Chip Select.
* Set the hardware-controlled native Chip Select to an invalid
* value to prevent it from interfering.
*/
if (gpio_is_valid(spi->cs_gpio) || (spi->mode & SPI_NO_CS))
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;

/* set transmit buffers and length */
bs->tx_buf = tfr->tx_buf;
Expand Down Expand Up @@ -624,59 +608,6 @@ static void bcm2835_spi_handle_err(struct spi_master *master,
bcm2835_spi_reset_hw(master);
}

static void bcm2835_spi_set_cs(struct spi_device *spi, bool gpio_level)
{
/*
* we can assume that we are "native" as per spi_set_cs
* calling us ONLY when cs_gpio is not set
* we can also assume that we are CS < 3 as per bcm2835_spi_setup
* we would not get called because of error handling there.
* the level passed is the electrical level not enabled/disabled
* so it has to get translated back to enable/disable
* see spi_set_cs in spi.c for the implementation
*/

struct spi_master *master = spi->master;
struct bcm2835_spi *bs = spi_master_get_devdata(master);
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
bool enable;

/* calculate the enable flag from the passed gpio_level */
enable = (spi->mode & SPI_CS_HIGH) ? gpio_level : !gpio_level;

/* set flags for "reverse" polarity in the registers */
if (spi->mode & SPI_CS_HIGH) {
/* set the correct CS-bits */
cs |= BCM2835_SPI_CS_CSPOL;
cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select;
} else {
/* clean the CS-bits */
cs &= ~BCM2835_SPI_CS_CSPOL;
cs &= ~(BCM2835_SPI_CS_CSPOL0 << spi->chip_select);
}

/* select the correct chip_select depending on disabled/enabled */
if (enable) {
/* set cs correctly */
if (spi->mode & SPI_NO_CS) {
/* use the "undefined" chip-select */
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
} else {
/* set the chip select */
cs &= ~(BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01);
cs |= spi->chip_select;
}
} else {
/* disable CSPOL which puts HW-CS into deselected state */
cs &= ~BCM2835_SPI_CS_CSPOL;
/* use the "undefined" chip-select as precaution */
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
}

/* finally set the calculated flags in SPI_CS */
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
}

static int chip_match_name(struct gpio_chip *chip, void *data)
{
return !strcmp(chip->label, data);
Expand Down Expand Up @@ -748,7 +679,6 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
master->bits_per_word_mask = SPI_BPW_MASK(8);
master->num_chipselect = 3;
master->setup = bcm2835_spi_setup;
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;
Expand Down

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