[PATCH v2 4/8] tegra: add lowlevel delay function

[Lucas Stach]

For proper startup we need to give clocks and IO signals some time to
stabilize. Tegra2 got away without them, but Tegra3 seems to be a bit
pickier.

Signed-off-by: Lucas Stach <dev at lynxeye.de>
---
 arch/arm/mach-tegra/include/mach/lowlevel.h | 44 +++++++++++++++++++++++++++++
 arch/arm/mach-tegra/tegra_avp_init.c        |  5 ++++
 2 files changed, 49 insertions(+)

diff --git a/arch/arm/mach-tegra/include/mach/lowlevel.h b/arch/arm/mach-tegra/include/mach/lowlevel.h
index 20de1b2..85ab7ef 100644
--- a/arch/arm/mach-tegra/include/mach/lowlevel.h
+++ b/arch/arm/mach-tegra/include/mach/lowlevel.h
@@ -183,6 +183,49 @@ int tegra_get_osc_clock(void)
 	}
 }
 
+#define TIMER_CNTR_1US	0x00
+#define TIMER_USEC_CFG	0x04
+
+static __always_inline
+void tegra_ll_delay_setup(void)
+{
+	u32 reg;
+
+	/*
+	 * calibrate timer to run at 1MHz
+	 * TIMERUS_USEC_CFG selects the scale down factor with bits [0:7]
+	 * representing the divisor and bits [8:15] representing the dividend
+	 * each in n+1 form.
+	 */
+	switch (tegra_get_osc_clock()) {
+	case 12000000:
+		reg = 0x000b;
+		break;
+	case 13000000:
+		reg = 0x000c;
+		break;
+	case 19200000:
+		reg = 0x045f;
+		break;
+	case 26000000:
+		reg = 0x0019;
+		break;
+	default:
+		reg = 0;
+		break;
+	}
+
+	writel(reg, TEGRA_TMRUS_BASE + TIMER_USEC_CFG);
+}
+
+static __always_inline
+void tegra_ll_delay_usec(int delay)
+{
+	int timeout = (int)readl(TEGRA_TMRUS_BASE + TIMER_CNTR_1US) + delay;
+
+	while ((int)readl(TEGRA_TMRUS_BASE + TIMER_CNTR_1US) - timeout < 0);
+}
+
 static __always_inline
 void tegra_cpu_lowlevel_setup(void)
 {
@@ -193,6 +236,7 @@ void tegra_cpu_lowlevel_setup(void)
 	r &= ~0x1f;
 	r |= 0xd3;
 	__asm__ __volatile__("msr cpsr, %0" : : "r"(r));
+	tegra_ll_delay_setup();
 }
 
 /* reset vector for the AVP, to be called from board reset vector */
diff --git a/arch/arm/mach-tegra/tegra_avp_init.c b/arch/arm/mach-tegra/tegra_avp_init.c
index 2c2d6fc..9f8ccf3 100644
--- a/arch/arm/mach-tegra/tegra_avp_init.c
+++ b/arch/arm/mach-tegra/tegra_avp_init.c
@@ -158,6 +158,9 @@ static void start_cpu0_clocks(void)
 	reg = readl(TEGRA_CLK_RESET_BASE + CRC_CLK_OUT_ENB_L);
 	reg |= CRC_CLK_OUT_ENB_L_CPU;
 	writel(reg, TEGRA_CLK_RESET_BASE + CRC_CLK_OUT_ENB_L);
+
+	/* give clocks some time to settle */
+	tegra_ll_delay_usec(300);
 }
 
 static void maincomplex_powerup(void)
@@ -175,6 +178,8 @@ static void maincomplex_powerup(void)
 		reg = readl(TEGRA_PMC_BASE + PMC_REMOVE_CLAMPING_CMD);
 		reg |= PMC_REMOVE_CLAMPING_CMD_CPU;
 		writel(reg, TEGRA_PMC_BASE + PMC_REMOVE_CLAMPING_CMD);
+
+		tegra_ll_delay_usec(1000);
 	}
 }
 void tegra_avp_reset_vector(uint32_t boarddata)
-- 
1.8.5.3