Re: [PATCH v2 1/2] ARM: shmobile: wait for MSTP clock status to toggle, when enabling it

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Guennadi,

Thanks for the patch.

On Thursday 13 June 2013 10:58:41 Guennadi Liakhovetski wrote:
> On r-/sh-mobile SoCs MSTP clocks are used by the runtime PM to dynamically
> enable and disable peripheral clocks. To make sure the clock has really
> started we have to read back its status register until it confirms success.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
> ---
> 
> v2:
> 1. removed "const" reom read accessors to fix compiler warnings
> 2. added a "(void __iomem *)" cast, as suggested by Laurent

After a quick review I'm wondering if it wouldn't make more sense to drop the 
cast and change the status_reg field type to phys_addr_t. The enable_reg field 
should probably be changed accordingly as well.

>  drivers/sh/clk/cpg.c   |   38 ++++++++++++++++++++++++++++++++++++++
>  include/linux/sh_clk.h |   29 +++++++++++++++++------------
>  2 files changed, 55 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/sh/clk/cpg.c b/drivers/sh/clk/cpg.c
> index 1ebe67c..87de622 100644
> --- a/drivers/sh/clk/cpg.c
> +++ b/drivers/sh/clk/cpg.c
> @@ -36,9 +36,47 @@ static void sh_clk_write(int value, struct clk *clk)
>  		iowrite32(value, clk->mapped_reg);
>  }
> 
> +static unsigned int r8(void __iomem *addr)
> +{
> +	return ioread8(addr);
> +}
> +
> +static unsigned int r16(void __iomem *addr)
> +{
> +	return ioread16(addr);
> +}
> +
> +static unsigned int r32(void __iomem *addr)
> +{
> +	return ioread32(addr);
> +}
> +
>  static int sh_clk_mstp_enable(struct clk *clk)
>  {
>  	sh_clk_write(sh_clk_read(clk) & ~(1 << clk->enable_bit), clk);
> +	if (clk->status_reg) {
> +		unsigned int (*read)(void __iomem *addr);
> +		int i;
> +		void __iomem *mapped_status = (phys_addr_t)clk->status_reg -
> +			(phys_addr_t)clk->enable_reg + clk->mapped_reg;
> +
> +		if (clk->flags & CLK_ENABLE_REG_8BIT)
> +			read = r8;
> +		else if (clk->flags & CLK_ENABLE_REG_16BIT)
> +			read = r16;
> +		else
> +			read = r32;
> +
> +		for (i = 1000;
> +		     (read(mapped_status) & (1 << clk->enable_bit)) && i;
> +		     i--)
> +			cpu_relax();
> +		if (!i) {
> +			pr_err("cpg: failed to enable %p[%d]\n",
> +			       clk->enable_reg, clk->enable_bit);
> +			return -ETIMEDOUT;
> +		}
> +	}
>  	return 0;
>  }
> 
> diff --git a/include/linux/sh_clk.h b/include/linux/sh_clk.h
> index 60c7239..affc8d8 100644
> --- a/include/linux/sh_clk.h
> +++ b/include/linux/sh_clk.h
> @@ -52,6 +52,7 @@ struct clk {
>  	unsigned long		flags;
> 
>  	void __iomem		*enable_reg;
> +	void __iomem		*status_reg;
>  	unsigned int		enable_bit;
>  	void __iomem		*mapped_reg;
> 
> @@ -116,22 +117,26 @@ long clk_round_parent(struct clk *clk, unsigned long
> target, unsigned long *best_freq, unsigned long *parent_freq,
>  		      unsigned int div_min, unsigned int div_max);
> 
> -#define SH_CLK_MSTP(_parent, _enable_reg, _enable_bit, _flags)		\
> -{									\
> -	.parent		= _parent,					\
> -	.enable_reg	= (void __iomem *)_enable_reg,			\
> -	.enable_bit	= _enable_bit,					\
> -	.flags		= _flags,					\
> +#define SH_CLK_MSTP(_parent, _enable_reg, _enable_bit, _status_reg,
> _flags)	\ +{										\
> +	.parent		= _parent,						\
> +	.enable_reg	= (void __iomem *)_enable_reg,				\
> +	.enable_bit	= _enable_bit,						\
> +	.status_reg	= (void __iomem *)_status_reg,				\
> +	.flags		= _flags,						\
>  }
> 
> -#define SH_CLK_MSTP32(_p, _r, _b, _f)					\
> -	SH_CLK_MSTP(_p, _r, _b, _f | CLK_ENABLE_REG_32BIT)
> +#define SH_CLK_MSTP32(_p, _r, _b, _f)				\
> +	SH_CLK_MSTP(_p, _r, _b, 0, _f | CLK_ENABLE_REG_32BIT)
> 
> -#define SH_CLK_MSTP16(_p, _r, _b, _f)					\
> -	SH_CLK_MSTP(_p, _r, _b, _f | CLK_ENABLE_REG_16BIT)
> +#define SH_CLK_MSTP32_STS(_p, _r, _b, _s, _f)			\
> +	SH_CLK_MSTP(_p, _r, _b, _s, _f | CLK_ENABLE_REG_32BIT)
> 
> -#define SH_CLK_MSTP8(_p, _r, _b, _f)					\
> -	SH_CLK_MSTP(_p, _r, _b, _f | CLK_ENABLE_REG_8BIT)
> +#define SH_CLK_MSTP16(_p, _r, _b, _f)				\
> +	SH_CLK_MSTP(_p, _r, _b, 0, _f | CLK_ENABLE_REG_16BIT)
> +
> +#define SH_CLK_MSTP8(_p, _r, _b, _f)				\
> +	SH_CLK_MSTP(_p, _r, _b, 0, _f | CLK_ENABLE_REG_8BIT)
> 
>  int sh_clk_mstp_register(struct clk *clks, int nr);
-- 
Regards,

Laurent Pinchart