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authorPeng Fan <Peng.Fan@freescale.com>2015-01-15 14:22:32 +0800
committerStefano Babic <sbabic@denx.de>2015-02-17 10:42:53 +0100
commit1f516faa45611aedc8c2e3f303b3866f615d481e (patch)
treea6a1894153196675b626c327c927d667201a6d25
parente72d344386bf80738fab7a6bd37cb321f443093a (diff)
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ARM: imx6: disable bandgap self-bias after boot
The self-bias circuit is used by the bandgap during startup. Once the bandgap has stabilized, the self-bias circuit should be disabled for best noise performance of analog blocks. Also this bit should be disabled before the chip enters STOP mode or when ever the regular bandgap is disabled. Signed-off-by: Peng Fan <Peng.Fan@freescale.com> Signed-off-by: Ranjani Vaidyanathan <Ranjani.Vaidyanathan@freescale.com>
-rw-r--r--arch/arm/cpu/armv7/mx6/soc.c24
-rw-r--r--arch/arm/include/asm/arch-mx6/crm_regs.h2
2 files changed, 26 insertions, 0 deletions
diff --git a/arch/arm/cpu/armv7/mx6/soc.c b/arch/arm/cpu/armv7/mx6/soc.c
index e599a12..df4e824 100644
--- a/arch/arm/cpu/armv7/mx6/soc.c
+++ b/arch/arm/cpu/armv7/mx6/soc.c
@@ -255,6 +255,23 @@ static void clear_mmdc_ch_mask(void)
writel(0, &mxc_ccm->ccdr);
}
+static void init_bandgap(void)
+{
+ struct anatop_regs *anatop = (struct anatop_regs *)ANATOP_BASE_ADDR;
+ /*
+ * Ensure the bandgap has stabilized.
+ */
+ while (!(readl(&anatop->ana_misc0) & 0x80))
+ ;
+ /*
+ * For best noise performance of the analog blocks using the
+ * outputs of the bandgap, the reftop_selfbiasoff bit should
+ * be set.
+ */
+ writel(BM_ANADIG_ANA_MISC0_REFTOP_SELBIASOFF, &anatop->ana_misc0_set);
+}
+
+
#ifdef CONFIG_MX6SL
static void set_preclk_from_osc(void)
{
@@ -275,6 +292,13 @@ int arch_cpu_init(void)
clear_mmdc_ch_mask();
/*
+ * Disable self-bias circuit in the analog bandap.
+ * The self-bias circuit is used by the bandgap during startup.
+ * This bit should be set after the bandgap has initialized.
+ */
+ init_bandgap();
+
+ /*
* When low freq boot is enabled, ROM will not set AHB
* freq, so we need to ensure AHB freq is 132MHz in such
* scenario.
diff --git a/arch/arm/include/asm/arch-mx6/crm_regs.h b/arch/arm/include/asm/arch-mx6/crm_regs.h
index 39f3c07..0592ce0 100644
--- a/arch/arm/include/asm/arch-mx6/crm_regs.h
+++ b/arch/arm/include/asm/arch-mx6/crm_regs.h
@@ -1063,4 +1063,6 @@ struct mxc_ccm_reg {
#define BF_ANADIG_PFD_528_PFD0_FRAC(v) \
(((v) << 0) & BM_ANADIG_PFD_528_PFD0_FRAC)
+#define BM_ANADIG_ANA_MISC0_REFTOP_SELBIASOFF 0x00000008
+
#endif /*__ARCH_ARM_MACH_MX6_CCM_REGS_H__ */