[U-Boot] [PATCH 5/6] arm: mx5: Add NAND clock handling

[Marek Vasut]

Dear Benoît Thébaudeau,

> On Friday, April 19, 2013 11:02:03 AM, Benoît Thébaudeau wrote:
> > Dear Marek Vasut,
> > 
> > On Friday, April 19, 2013 6:10:54 AM, Marek Vasut wrote:
> > > Augment the MX5 clock code with function to enable and configure
> > > NFC clock. This is necessary to get NFC working on MX5.
> > > 
> > > Signed-off-by: Marek Vasut <marex at denx.de>
> > > Cc: Albert ARIBAUD <albert.u.boot at aribaud.net>
> > > Cc: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> > > Cc: Fabio Estevam <fabio.estevam at freescale.com>
> > > Cc: Scott Wood <scottwood at freescale.com>
> > > Cc: Stefano Babic <sbabic at denx.de>
> > > Cc: Tom Rini <trini at ti.com>
> > > ---
> > > 
> > >  arch/arm/cpu/armv7/mx5/clock.c        | 14 ++++++++++++--
> > >  arch/arm/include/asm/arch-mx5/clock.h |  1 +
> > >  2 files changed, 13 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm/cpu/armv7/mx5/clock.c
> > > b/arch/arm/cpu/armv7/mx5/clock.c
> > > index 76c2c52..431756e 100644
> > > --- a/arch/arm/cpu/armv7/mx5/clock.c
> > > +++ b/arch/arm/cpu/armv7/mx5/clock.c
> > > @@ -739,10 +739,11 @@ static int config_core_clk(u32 ref, u32 freq)
> > > 
> > >  static int config_nfc_clk(u32 nfc_clk)
> > >  {
> > >  
> > >  	u32 parent_rate = get_emi_slow_clk();
> > > 
> > > -	u32 div = parent_rate / nfc_clk;
> > > +	u32 div;
> > > 
> > > -	if (nfc_clk <= 0)
> > > +	if (nfc_clk == 0)
> > > 
> > >  		return -EINVAL;
> > > 
> > > +	div = parent_rate / nfc_clk;
> > > 
> > >  	if (div == 0)
> > >  	
> > >  		div++;
> > >  	
> > >  	if (parent_rate / div > NFC_CLK_MAX)
> > > 
> > > @@ -755,6 +756,15 @@ static int config_nfc_clk(u32 nfc_clk)
> > > 
> > >  	return 0;
> > >  
> > >  }
> > > 
> > > +void enable_nfc_clk(unsigned char enable)
> > > +{
> > > +	unsigned int cg = enable ? MXC_CCM_CCGR_CG_ON : MXC_CCM_CCGR_CG_OFF;
> > > +
> > > +	clrsetbits_le32(&mxc_ccm->CCGR5,
> > > +		MXC_CCM_CCGR5_EMI_ENFC(MXC_CCM_CCGR_CG_MASK),
> > > +		MXC_CCM_CCGR5_EMI_ENFC(cg));
> > > +}
> > > +
> > > 
> > >  /* Config main_bus_clock for periphs */
> > >  static int config_periph_clk(u32 ref, u32 freq)
> > >  {
> > > 
> > > diff --git a/arch/arm/include/asm/arch-mx5/clock.h
> > > b/arch/arm/include/asm/arch-mx5/clock.h
> > > index 9cdfb48..6910192 100644
> > > --- a/arch/arm/include/asm/arch-mx5/clock.h
> > > +++ b/arch/arm/include/asm/arch-mx5/clock.h
> > > @@ -68,5 +68,6 @@ void set_usboh3_clk(void);
> > > 
> > >  void enable_usboh3_clk(unsigned char enable);
> > >  void mxc_set_sata_internal_clock(void);
> > >  int enable_i2c_clk(unsigned char enable, unsigned i2c_num);
> > > 
> > > +void enable_nfc_clk(unsigned char enable);
> > > 
> > >  #endif /* __ASM_ARCH_CLOCK_H */
> > > 
> > > --
> > > 1.7.11.7
> > 
> > Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> 
> Actually, this code is correct, but why is it needed? Indeed, this clock is
> already ungated by arch/arm/cpu/armv7/mx5/lowlevel_init.S.

This is not good, the code should be moved away from the assembly.

> Also, your board
> seems to be hardware-bootable only from NAND

This is incorrect, it is bootable from SD card as well.

> so in this case the boot ROM
> also ungates this clock itself.

We can not rely on that.