From 74e1d8fd01024d3fbbe915fee7ab24ecb781b687 Mon Sep 17 00:00:00 2001 From: Peng Fan Date: Thu, 15 Jan 2015 14:22:32 +0800 Subject: [PATCH] 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 Signed-off-by: Ranjani Vaidyanathan --- arch/arm/cpu/armv7/mx6/soc.c | 23 +++++++++++++++++++++++ arch/arm/include/asm/arch-mx6/crm_regs.h | 2 ++ 2 files changed, 25 insertions(+) diff --git a/arch/arm/cpu/armv7/mx6/soc.c b/arch/arm/cpu/armv7/mx6/soc.c index ee035c576e..2fe069ec24 100644 --- a/arch/arm/cpu/armv7/mx6/soc.c +++ b/arch/arm/cpu/armv7/mx6/soc.c @@ -450,6 +450,22 @@ 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_SOC_MX6SL static void set_preclk_from_osc(void) { @@ -469,6 +485,13 @@ int arch_cpu_init(void) /* Need to clear MMDC_CHx_MASK to make warm reset work. */ 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 diff --git a/arch/arm/include/asm/arch-mx6/crm_regs.h b/arch/arm/include/asm/arch-mx6/crm_regs.h index ce465c6179..89481a1a86 100644 --- a/arch/arm/include/asm/arch-mx6/crm_regs.h +++ b/arch/arm/include/asm/arch-mx6/crm_regs.h @@ -1352,4 +1352,6 @@ struct mxc_ccm_reg { (((v) << BP_ANADIG_PFD_528_PFD0_FRAC) & \ BM_ANADIG_PFD_528_PFD0_FRAC) +#define BM_ANADIG_ANA_MISC0_REFTOP_SELBIASOFF 0x00000008 + #endif /*__ARCH_ARM_MACH_MX6_CCM_REGS_H__ */ -- 2.39.2