mmc: stm32: sdmmc2: add hardware flow control support

The hardware flow control functionality is used to avoid
FIFO underrun (TX mode) and overrun (RX mode) errors.
The behavior is to stop SDMMC_CK during data transfer and
freeze the SDMMC state machines.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

drivers/mmc/stm32_sdmmc2.c

@@ -495,7 +495,8 @@ static int stm32_sdmmc2_set_ios(struct udevice *dev)
 	if (mmc->bus_width == 8)
 		clk |= SDMMC_CLKCR_WIDBUS_8;
 
-	writel(clk | priv->clk_reg_msk, priv->base + SDMMC_CLKCR);
+	writel(clk | priv->clk_reg_msk | SDMMC_CLKCR_HWFC_EN,
+	       priv->base + SDMMC_CLKCR);
 
 	return 0;
 }