spi: rockchip: Support 64-location deep FIFOs

The FIFO depth of SPI V2 is 64 instead of 32, add support for it.
Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Tested-by: Emil Renner Berthing <kernel@esmil.dk>
Reviewed-by: Emil Renner Berthing <kernel@esmil.dk>
Link: https://lore.kernel.org/r/20200723004356.6390-2-jon.lin@rock-chips.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rockchip.c

@@ -39,8 +39,9 @@
 #define ROCKCHIP_SPI_RISR			0x0034
 #define ROCKCHIP_SPI_ICR			0x0038
 #define ROCKCHIP_SPI_DMACR			0x003c
-#define ROCKCHIP_SPI_DMATDLR		0x0040
-#define ROCKCHIP_SPI_DMARDLR		0x0044
+#define ROCKCHIP_SPI_DMATDLR			0x0040
+#define ROCKCHIP_SPI_DMARDLR			0x0044
+#define ROCKCHIP_SPI_VERSION			0x0048
 #define ROCKCHIP_SPI_TXDR			0x0400
 #define ROCKCHIP_SPI_RXDR			0x0800
 
@@ -156,6 +157,8 @@
 #define ROCKCHIP_SPI_MAX_TRANLEN		0xffff
 
 #define ROCKCHIP_SPI_MAX_CS_NUM			2
+#define ROCKCHIP_SPI_VER2_TYPE1			0x05EC0002
+#define ROCKCHIP_SPI_VER2_TYPE2			0x00110002
 
 struct rockchip_spi {
 	struct device *dev;
@@ -206,17 +209,17 @@ static inline void wait_for_idle(struct rockchip_spi *rs)
 
 static u32 get_fifo_len(struct rockchip_spi *rs)
 {
-	u32 fifo;
+	u32 ver;
 
-	for (fifo = 2; fifo < 32; fifo++) {
-		writel_relaxed(fifo, rs->regs + ROCKCHIP_SPI_TXFTLR);
-		if (fifo != readl_relaxed(rs->regs + ROCKCHIP_SPI_TXFTLR))
-			break;
-	}
-
-	writel_relaxed(0, rs->regs + ROCKCHIP_SPI_TXFTLR);
+	ver = readl_relaxed(rs->regs + ROCKCHIP_SPI_VERSION);
 
-	return (fifo == 31) ? 0 : fifo;
+	switch (ver) {
+	case ROCKCHIP_SPI_VER2_TYPE1:
+	case ROCKCHIP_SPI_VER2_TYPE2:
+		return 64;
+	default:
+		return 32;
+	}
 }
 
 static void rockchip_spi_set_cs(struct spi_device *spi, bool enable)