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

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

[Michael Heimpold]

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.

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()
+ *
+ * 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);
 #endif
 
 struct mxs_pair {
-- 
2.5.0

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

[Marek Vasut]

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.

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

[Michael Heimpold]

Hi Marek,

Am Saturday 12 December 2015, 02:42:47 schrieb Marek Vasut:
> 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?

Sure. Every DC-DC switching frequency also generates some harmonics.
On usual board design, this is not a huge problem, but on our I2SE
Duckbill EnOcean devices, the EnOcean transceiver sits very close to the
i.MX because of stacked PCBs. Our hardware guys measured, that the
harmonics overlaps a little bit with the EnOcean spectrum. Changing
the DC-DC frequency results in others harmonics, which do not interfere
anymore.
I already sent a patch for adding Duckbill support and I'm preparing a v2
which would include this topic, so this would be the first user of this 
feature.

> 
> > 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.

Ah, yes. Will do in v3.

> 
> > + * 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.

mxs_power_setup_dcdc_clocksource is the weak function, not 
mxs_power_select_dcdc_clocksource so I think this is needed.

Regards,
Michael

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

[Marek Vasut]

On Saturday, December 12, 2015 at 10:02:30 AM, Michael Heimpold wrote:
> Hi Marek,

Hi!

> Am Saturday 12 December 2015, 02:42:47 schrieb Marek Vasut:
> > 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?
> 
> Sure. Every DC-DC switching frequency also generates some harmonics.
> On usual board design, this is not a huge problem, but on our I2SE
> Duckbill EnOcean devices, the EnOcean transceiver sits very close to the
> i.MX because of stacked PCBs. Our hardware guys measured, that the
> harmonics overlaps a little bit with the EnOcean spectrum. Changing
> the DC-DC frequency results in others harmonics, which do not interfere
> anymore.
> I already sent a patch for adding Duckbill support and I'm preparing a v2
> which would include this topic, so this would be the first user of this
> feature.

Ah, thanks for the detailed explanation, got it.

> > > 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)
> > > +{

Looks like the comment and name of the function do not match here ("select" vs 
"switch").

> > > +	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.
> 
> Ah, yes. Will do in v3.
> 
> > > + * 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");

Shouldn't this call the mxs_power_select_dcdc_clocksource() then somehow ?

> > > +}
> > > +
> > > +/**
> > > 
> > >   * 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.
> 
> mxs_power_setup_dcdc_clocksource is the weak function, not
> mxs_power_select_dcdc_clocksource so I think this is needed.

So the user is supposed to call this function from the board code, right?

Best regards,
Marek Vasut