arm: mvebu: set 38x and 39x AVS on lower frequency

Reduce Auto Voltage Scaling VDD limit when core frequency is lower than
1600MHz. This reduces core voltage level from 1.25V to 1.15V, which
saves power.

The code is taken from Marvell's U-Boot 2013.01 revision 18.06.

Reviewed-by: Chris Packham <judge.packham@gmail.com>
Tested-by: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>

4 files changed, 40 insertions, 0 deletions

diff --git a/arch/arm/mach-mvebu/include/mach/cpu.h b/arch/arm/mach-mvebu/include/mach/cpu.h
index e6140d6729..2e2d72aac8 100644
--- a/arch/arm/mach-mvebu/include/mach/cpu.h
+++ b/arch/arm/mach-mvebu/include/mach/cpu.h
@@ -163,6 +163,13 @@ int serdes_phy_config(void);
  */
 int ddr3_init(void);
 
+/* Auto Voltage Scaling */
+#if defined(CONFIG_ARMADA_38X) || defined(CONFIG_ARMADA_39X)
+void mv_avs_init(void);
+#else
+static inline void mv_avs_init(void) {}
+#endif
+
 /*
  * get_ref_clk
  *
diff --git a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
index d387893af3..e9dd096ad0 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
+++ b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
@@ -256,3 +256,29 @@ u8 sys_env_device_rev_get(void)
 	value = reg_read(DEV_VERSION_ID_REG);
 	return (value & (REVISON_ID_MASK)) >> REVISON_ID_OFFS;
 }
+
+void mv_avs_init(void)
+{
+	u32 sar_freq;
+
+	if (!(IS_ENABLED(CONFIG_ARMADA_38X) || IS_ENABLED(CONFIG_ARMADA_39X)))
+		return;
+
+	reg_write(AVS_DEBUG_CNTR_REG, AVS_DEBUG_CNTR_DEFAULT_VALUE);
+	reg_write(AVS_DEBUG_CNTR_REG, AVS_DEBUG_CNTR_DEFAULT_VALUE);
+
+	sar_freq = reg_read(DEVICE_SAMPLE_AT_RESET1_REG);
+	sar_freq = sar_freq >> SAR_FREQ_OFFSET & SAR_FREQ_MASK;
+
+	/* Set AVS value only for core frequency of 1600MHz or less.
+	 * For higher frequency leave the default value.
+	 */
+	if (sar_freq <= 0xd) {
+		u32 avs_reg_data = reg_read(AVS_ENABLED_CONTROL);
+
+		avs_reg_data &= ~(AVS_LOW_VDD_LIMIT_MASK
+				| AVS_HIGH_VDD_LIMIT_MASK);
+		avs_reg_data |= AVS_LOW_VDD_SLOW_VAL | AVS_HIGH_VDD_SLOW_VAL;
+		reg_write(AVS_ENABLED_CONTROL, avs_reg_data);
+	}
+}
diff --git a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
index 365332d2b0..1774a5b780 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
+++ b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
@@ -33,6 +33,8 @@
 #define DEV_ID_REG_DEVICE_ID_OFFS	16
 #define DEV_ID_REG_DEVICE_ID_MASK	0xffff0000
 
+#define SAR_FREQ_OFFSET			10
+#define SAR_FREQ_MASK			0x1f
 #define SAR_DEV_ID_OFFS			27
 #define SAR_DEV_ID_MASK			0x7
 
@@ -155,10 +157,12 @@
 #define AVS_LOW_VDD_LIMIT_OFFS		4
 #define AVS_LOW_VDD_LIMIT_MASK		(0xff << AVS_LOW_VDD_LIMIT_OFFS)
 #define AVS_LOW_VDD_LIMIT_VAL		(0x27 << AVS_LOW_VDD_LIMIT_OFFS)
+#define AVS_LOW_VDD_SLOW_VAL		(0x23 << AVS_LOW_VDD_LIMIT_OFFS)
 
 #define AVS_HIGH_VDD_LIMIT_OFFS		12
 #define AVS_HIGH_VDD_LIMIT_MASK		(0xff << AVS_HIGH_VDD_LIMIT_OFFS)
 #define AVS_HIGH_VDD_LIMIT_VAL		(0x27 << AVS_HIGH_VDD_LIMIT_OFFS)
+#define AVS_HIGH_VDD_SLOW_VAL		(0x23 << AVS_HIGH_VDD_LIMIT_OFFS)
 
 /* Board ID numbers */
 #define MARVELL_BOARD_ID_MASK		0x10
diff --git a/arch/arm/mach-mvebu/spl.c b/arch/arm/mach-mvebu/spl.c
index d54de51956..3cb27b7f4b 100644
--- a/arch/arm/mach-mvebu/spl.c
+++ b/arch/arm/mach-mvebu/spl.c
@@ -126,6 +126,9 @@ void board_init_f(ulong dummy)
 	ddr3_init();
 #endif
 
+	/* Initialize Auto Voltage Scaling */
+	mv_avs_init();
+
 	/*
 	 * Return to the BootROM to continue the Marvell xmodem
 	 * UART boot protocol. As initiated by the kwboot tool.