allwinner: A64/H5: setup missing bus clocks

The legacy Allwinner ATF port used to setup some clocks, and U-Boot is
still relying on this. We don't need to setup the full set, as the SPL
is doing most of it, but it misses one clock (AHB2) and programs another
(AHB1) to quite conservative values.

Fix this up during the platform setup to improve USB and Ethernet
performance, iperf values go up by 31% in my setup with that patch.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/allwinner/common/sunxi_bl31_setup.c

@@ -11,6 +11,7 @@
 #include <generic_delay_timer.h>
 #include <gicv2.h>
 #include <libfdt.h>
+#include <mmio.h>
 #include <platform.h>
 #include <platform_def.h>
 #include <sunxi_def.h>
@@ -148,6 +149,25 @@ void bl31_platform_setup(void)
 
 	sunxi_security_setup();
 
+	/*
+	 * On the A64 U-Boot's SPL sets the bus clocks to some conservative
+	 * values, to work around FEL mode instabilities with SRAM C accesses.
+	 * FEL mode is gone when we reach ATF, so bring the AHB1 bus
+	 * (the "main" bus) clock frequency back to the recommended 200MHz,
+	 * for improved performance.
+	 */
+	if (soc_id == SUNXI_SOC_A64)
+		mmio_write_32(SUNXI_CCU_BASE + 0x54, 0x00003180);
+
+	/*
+	 * U-Boot or the kernel don't setup AHB2, which leaves it at the
+	 * AHB1 frequency (200 MHz, see above). However Allwinner recommends
+	 * 300 MHz, for improved Ethernet and USB performance. Switch the
+	 * clock to use "PLL_PERIPH0 / 2".
+	 */
+	if (soc_id == SUNXI_SOC_A64 || soc_id == SUNXI_SOC_H5)
+		mmio_write_32(SUNXI_CCU_BASE + 0x5c, 0x1);
+
 	sunxi_pmic_setup(soc_id, fdt);
 
 	INFO("BL31: Platform setup done\n");