[U-Boot] [PATCH v2] ARM: mxs: allow boards to select DC-DC switching clock source

[Marek Vasut <marex@denx.de>]

On Friday, December 11, 2015 at 12:05:36 AM, Michael Heimpold wrote:
> For some board designs, it might be useful to switch the DC-DC
> clock source to something else rather the default 24 MHz, e.g.
> for EMI reasons.

Can you elaborate on this ? Also, is there gonna be a user for this?

> For this, override the mxs_power_setup_dcdc_clocksource function
> in your board support files.
> 
> Example:
> void mxs_power_setup_dcdc_clocksource(void)
> {
>     mxs_power_select_dcdc_clocksource(POWER_MISC_FREQSEL_20MHZ);
> }
> 
> Signed-off-by: Michael Heimpold <mhei@heimpold.de>
> Cc: Marek Vasut <marex@denx.de>
> Cc: Otavio Salvador <otavio@ossystems.com.br>
> Cc: Fabio Estevam <fabio.estevam@freescale.com>
> ---
> 
> Changes in v2:
>   - use a weak function approach instead of ifdef'ery as suggested
>     by Marek Vasut
> 
>  arch/arm/cpu/arm926ejs/mxs/spl_power_init.c | 31
> +++++++++++++++++++++++++++++ arch/arm/include/asm/arch-mxs/sys_proto.h  
> |  2 ++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
> b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c index 1972de8..64e215c
> 100644
> --- a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
> +++ b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
> @@ -248,6 +248,36 @@ static void mxs_power_setup_5v_detect(void)
>  }
> 
>  /**
> + * mxs_power_switch_dcdc_clocksource() - Switch PLL clock for DC-DC
> converters + *
> + * This function configures and then enables an alternative PLL clock
> source + * for the DC-DC converters.
> + */
> +void mxs_power_select_dcdc_clocksource(uint32_t freqsel)
> +{
> +	struct mxs_power_regs *power_regs =
> +		(struct mxs_power_regs *)MXS_POWER_BASE;
> +
> +	/* Select clocksource for DC-DC converters */
> +	clrsetbits_le32(&power_regs->hw_power_misc,
> +			POWER_MISC_FREQSEL_MASK,
> +			freqsel);
> +	setbits_le32(&power_regs->hw_power_misc,
> +			POWER_MISC_SEL_PLLCLK);
> +}
> +
> +/**
> + * mxs_power_setup_dcdc_clocksource()

Please make sure this is compatible with kerneldoc.

> + * Normally, there is no need to switch DC-DC clocksource. However, boards
> + * can implement this function when required.
> + */
> +__weak void mxs_power_setup_dcdc_clocksource(void)
> +{
> +	debug("SPL: Using default DC-DC clocksource\n");
> +}
> +
> +/**
>   * mxs_src_power_init() - Preconfigure the power block
>   *
>   * This function configures reasonable values for the DC-DC control loop
> @@ -872,6 +902,7 @@ static void mxs_power_configure_power_source(void)
> 
>  	debug("SPL: Configuring power source\n");
> 
> +	mxs_power_setup_dcdc_clocksource();
>  	mxs_src_power_init();
> 
>  	if (readl(&power_regs->hw_power_sts) & POWER_STS_VDD5V_GT_VDDIO) {
> diff --git a/arch/arm/include/asm/arch-mxs/sys_proto.h
> b/arch/arm/include/asm/arch-mxs/sys_proto.h index 20ff101..4160e43 100644
> --- a/arch/arm/include/asm/arch-mxs/sys_proto.h
> +++ b/arch/arm/include/asm/arch-mxs/sys_proto.h
> @@ -25,6 +25,8 @@ int mxsmmc_initialize(bd_t *bis, int id, int (*wp)(int),
> int (*cd)(int)); void mxs_common_spl_init(const uint32_t arg, const
> uint32_t *resptr, const iomux_cfg_t *iomux_setup,
>  			 const unsigned int iomux_size);
> +
> +void mxs_power_select_dcdc_clocksource(uint32_t freqsel);

This function does not need to be exported if it's __weak I believe.