spi/bcm63xx: make spi subsystem aware of message size limits

The bcm63xx SPI controller does not allow manual control of the CS
lines and will toggle it automatically before and after sending data,
so we are limited to messages that fit in the FIFO buffer. Since the CS
lines aren't available as GPIOs either, we will need to make slave
drivers aware of this limitation so they can handle them accordingly.

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm63xx.c

@@ -428,6 +428,13 @@ static irqreturn_t bcm63xx_spi_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static size_t bcm63xx_spi_max_length(struct spi_device *dev)
+{
+	struct bcm63xx_spi *bs = spi_master_get_devdata(spi->master);
+
+	return bs->fifo_size;
+}
+
 static const unsigned long bcm6348_spi_reg_offsets[] = {
 	[SPI_CMD]		= SPI_6348_CMD,
 	[SPI_INT_STATUS]	= SPI_6348_INT_STATUS,
@@ -541,6 +548,8 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
 	master->transfer_one_message = bcm63xx_spi_transfer_one;
 	master->mode_bits = MODEBITS;
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
+	master->max_transfer_size = bcm63xx_spi_max_length;
+	master->max_message_size = bcm63xx_spi_max_length;
 	master->auto_runtime_pm = true;
 	bs->msg_type_shift = bs->reg_offsets[SPI_MSG_TYPE_SHIFT];
 	bs->msg_ctl_width = bs->reg_offsets[SPI_MSG_CTL_WIDTH];