spi: bcm2835: Drop unused code for native Chip Select

Commit a30a555d7435 ("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>

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 43c6ca5..99797bb 100644 (file)
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -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);
 
@@ -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;
@@ -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;
@@ -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);
@@ -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;