spi: s3c64xx: allow FIFO depth to be determined from the compatible

There are SoCs that use the same FIFO depth for all the instances of the
SPI IP. See the fifo_lvl_mask defined for gs101 for example:
    .fifo_lvl_mask  = { 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
                        0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f},

Instead of specifying the FIFO depth with the same value for all 16
nodes in this case, allow such SoCs to infer the FIFO depth from the
compatible. There are other SoCs than can benefit of this, see:
{gs101, fsd, exynos850, s3c641, s3c2443}_spi_port_config.

The FIFO depth inferred from the compatible has a higher precedence than
the one that might be specified via device tree, the driver shall know
better.
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://msgid.link/r/20240216070555.2483977-7-tudor.ambarus@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-s3c64xx.c

@@ -137,6 +137,7 @@ struct s3c64xx_spi_dma_data {
  * struct s3c64xx_spi_port_config - SPI Controller hardware info
  * @fifo_lvl_mask: Bit-mask for {TX|RX}_FIFO_LVL bits in SPI_STATUS register.
  * @rx_lvl_offset: Bit offset of RX_FIFO_LVL bits in SPI_STATUS regiter.
+ * @fifo_depth: depth of the FIFO.
  * @rx_fifomask: SPI_STATUS.RX_FIFO_LVL mask. Shifted mask defining the field's
  *               length and position.
  * @tx_fifomask: SPI_STATUS.TX_FIFO_LVL mask. Shifted mask defining the field's
@@ -159,6 +160,7 @@ struct s3c64xx_spi_dma_data {
 struct s3c64xx_spi_port_config {
 	int	fifo_lvl_mask[MAX_SPI_PORTS];
 	int	rx_lvl_offset;
+	unsigned int fifo_depth;
 	u32	rx_fifomask;
 	u32	tx_fifomask;
 	int	tx_st_done;
@@ -1263,8 +1265,10 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
 		sdd->port_id = pdev->id;
 	}
 
-	if (of_property_read_u32(pdev->dev.of_node, "fifo-depth",
-				 &sdd->fifo_depth))
+	if (sdd->port_conf->fifo_depth)
+		sdd->fifo_depth = sdd->port_conf->fifo_depth;
+	else if (of_property_read_u32(pdev->dev.of_node, "fifo-depth",
+				      &sdd->fifo_depth))
 		sdd->fifo_depth = FIFO_DEPTH(sdd);
 
 	s3c64xx_spi_set_fifomask(sdd);