spi: sunxi: expose maximum transfer size limit

The sun4i spi hardware can trasfer at most 63 bytes of data without DMA
support so report the limitation. Same for sun6i.
Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-sun4i.c

@@ -167,6 +167,11 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
 	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);
 }
 
+static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
+{
+	return SUN4I_FIFO_DEPTH - 1;
+}
+
 static int sun4i_spi_transfer_one(struct spi_master *master,
 				  struct spi_device *spi,
 				  struct spi_transfer *tfr)
@@ -394,6 +399,7 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
 	master->dev.of_node = pdev->dev.of_node;
 	master->auto_runtime_pm = true;
+	master->max_transfer_size = sun4i_spi_max_transfer_size;
 
 	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
 	if (IS_ERR(sspi->hclk)) {

drivers/spi/spi-sun6i.c

@@ -153,6 +153,10 @@ static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
 	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);
 }
 
+static size_t sun6i_spi_max_transfer_size(struct spi_device *spi)
+{
+	return SUN6I_FIFO_DEPTH - 1;
+}
 
 static int sun6i_spi_transfer_one(struct spi_master *master,
 				  struct spi_device *spi,
@@ -393,6 +397,7 @@ static int sun6i_spi_probe(struct platform_device *pdev)
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
 	master->dev.of_node = pdev->dev.of_node;
 	master->auto_runtime_pm = true;
+	master->max_transfer_size = sun6i_spi_max_transfer_size;
 
 	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
 	if (IS_ERR(sspi->hclk)) {