dw_mmc: Calculate dwmmc FIFO threshold size if not provided

We can calculate this. Add code to do this if it is not provided.

panto: prefix changed to dw_mmc to make things easier to grep

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>

drivers/mmc/dw_mmc.c

@@ -373,9 +373,15 @@ static int dwmci_init(struct mmc *mmc)
 	dwmci_writel(host, DWMCI_IDINTEN, 0);
 	dwmci_writel(host, DWMCI_BMOD, 1);
 
-	if (host->fifoth_val) {
-		dwmci_writel(host, DWMCI_FIFOTH, host->fifoth_val);
+	if (!host->fifoth_val) {
+		uint32_t fifo_size;
+
+		fifo_size = dwmci_readl(host, DWMCI_FIFOTH);
+		fifo_size = ((fifo_size & RX_WMARK_MASK) >> RX_WMARK_SHIFT) + 1;
+		host->fifoth_val = MSIZE(0x2) | RX_WMARK(fifo_size / 2 - 1) |
+				TX_WMARK(fifo_size / 2);
 	}
+	dwmci_writel(host, DWMCI_FIFOTH, host->fifoth_val);
 
 	dwmci_writel(host, DWMCI_CLKENA, 0);
 	dwmci_writel(host, DWMCI_CLKSRC, 0);