drivers: mmc: sunxi: limit A64 MMC2 to 8K DMA buffer

Unlike the A64 user manual reports, the third MMC controller on the
A64 (and the only one capable of 8-bit HS400 eMMC transfers) has a
DMA buffer size limit of 8KB (much like the very old Allwinner SoCs).
This does not affect the other two controllers, so introduce a new
DT compatible string to let the driver use different settings for that
particular device.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi

@@ -343,8 +343,7 @@
 		};
 
 		mmc2: mmc@1c11000 {
-			compatible = "allwinner,sun50i-a64-mmc",
-				     "allwinner,sun5i-a13-mmc";
+			compatible = "allwinner,sun50i-a64-emmc";
 			reg = <0x01c11000 0x1000>;
 			clocks = <&ccu CLK_BUS_MMC2>, <&ccu CLK_MMC2>;
 			clock-names = "ahb", "mmc";

drivers/mmc/host/sunxi-mmc.c

@@ -1095,12 +1095,19 @@ static const struct sunxi_mmc_cfg sun50i_a64_cfg = {
 	.can_calibrate = true,
 };
 
+static const struct sunxi_mmc_cfg sun50i_a64_emmc_cfg = {
+	.idma_des_size_bits = 13,
+	.clk_delays = sun50i_mmc_clk_delays,
+	.can_calibrate = true,
+};
+
 static const struct of_device_id sunxi_mmc_of_match[] = {
 	{ .compatible = "allwinner,sun4i-a10-mmc", .data = &sun4i_a10_cfg },
 	{ .compatible = "allwinner,sun5i-a13-mmc", .data = &sun5i_a13_cfg },
 	{ .compatible = "allwinner,sun7i-a20-mmc", .data = &sun7i_a20_cfg },
 	{ .compatible = "allwinner,sun9i-a80-mmc", .data = &sun9i_a80_cfg },
 	{ .compatible = "allwinner,sun50i-a64-mmc", .data = &sun50i_a64_cfg },
+	{ .compatible = "allwinner,sun50i-a64-emmc", .data = &sun50i_a64_emmc_cfg },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, sunxi_mmc_of_match);