spi: rockchip-sfc: Optimize the judgment mechanism completed by the controller

There is very little data left in fifo, and the controller will
complete the transmission in a short period of time, so
use readl_poll_timeout() for busy wait 10us to accelerate response.

Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Link: https://patch.msgid.link/20241203013513.2628810-1-jon.lin@rock-chips.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Jon Lin

drivers/spi/spi-rockchip-sfc.c

@@ -472,6 +472,16 @@ static int rockchip_sfc_xfer_done(struct rockchip_sfc *sfc, u32 timeout_us)
 	int ret = 0;
 	u32 status;
 
+	/*
+	 * There is very little data left in fifo, and the controller will
+	 * complete the transmission in a short period of time.
+	 */
+	ret = readl_poll_timeout(sfc->regbase + SFC_SR, status,
+				 !(status & SFC_SR_IS_BUSY),
+				 0, 10);
+	if (!ret)
+		return 0;
+
 	ret = readl_poll_timeout(sfc->regbase + SFC_SR, status,
 				 !(status & SFC_SR_IS_BUSY),
 				 20, timeout_us);