Re: [PATCH] ARM: Samsung SoC: clksrc-clk: wait for the stable SRC/DIV status.

[Ben Dooks <ben@simtec.co.uk>]

On 28/07/10 04:17, MyungJoo Ham wrote:
> Many MUX and clock dividers have a status bit so that users can wait
> until the status is stable. When corresponding registers are accessed
> while a clock is not stable, we may suffer from unexpected errors.
> 
> Therefore, we introduce a mechanism to let the operations related with
> updating SRC/DIV registers of clksrc-clk wait for the stabilization:
> clk_set_parent, clk_set_rate.
> 
> In order to use this feature, the definition of clksrc_clk should
> include reg_src_stable or reg_div_stable. With effective rec_src_stable
> values, clk_set_parent returns with a stabilized SRC register and
> with effective rec_div_stable values, clk_set_rate returns with a
> stabilized DIV register. If .reg field is null, its (either SRC or DIV)
> register's status is not checked and returned without waiting; i.e.,
> some MUX/DIV may not need this feature.
> 
> When setting reg_*_stable, .size is used to tell the value of "stable".
> If .size = 0, the stable status is 0 and if .size = 1, the stable status
> is 1.
> 
> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
>  arch/arm/plat-samsung/clock-clksrc.c              |   13 +++++++++++++
>  arch/arm/plat-samsung/include/plat/clock-clksrc.h |   10 ++++++++++
>  2 files changed, 23 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/plat-samsung/clock-clksrc.c b/arch/arm/plat-samsung/clock-clksrc.c
> index 46d204a..5ff17ad 100644
> --- a/arch/arm/plat-samsung/clock-clksrc.c
> +++ b/arch/arm/plat-samsung/clock-clksrc.c
> @@ -68,6 +68,12 @@ static int s3c_setrate_clksrc(struct clk *clk, unsigned long rate)
>  	val |= (div - 1) << sclk->reg_div.shift;
>  	__raw_writel(val, reg);
>  
> +	if (sclk->reg_div_stable.reg) {
> +		do { } while (((__raw_readl(sclk->reg_div_stable.reg) >>
> +						sclk->reg_div_stable.shift) & 1)
> +				!= sclk->reg_div_stable.size);
> +	}
> +
>  	return 0;
>  }

you could move the code for this out to a separate inlined function to
avoid it being here twice, and possibly make it flow better.

> @@ -93,6 +99,13 @@ static int s3c_setparent_clksrc(struct clk *clk, struct clk *parent)
>  		clksrc |= src_nr << sclk->reg_src.shift;
>  
>  		__raw_writel(clksrc, sclk->reg_src.reg);
> +
> +		if (sclk->reg_src_stable.reg) {
> +			do { } while (((__raw_readl(sclk->reg_src_stable.reg) >>
> +						sclk->reg_src_stable.shift) & 1)
> +					!= sclk->reg_src_stable.size);
> +		}
> +
>  		return 0;
>  	}
>  
> diff --git a/arch/arm/plat-samsung/include/plat/clock-clksrc.h b/arch/arm/plat-samsung/include/plat/clock-clksrc.h
> index 50a8ca7..282821d 100644
> --- a/arch/arm/plat-samsung/include/plat/clock-clksrc.h
> +++ b/arch/arm/plat-samsung/include/plat/clock-clksrc.h
> @@ -45,6 +45,13 @@ struct clksrc_reg {
>   * @sources: the sources for this clock
>   * @reg_src: the register definition for selecting the clock's source
>   * @reg_div: the register definition for the clock's output divisor
> + * @reg_src_stable: the register definition to probe if reg_src is
> + *    stabilized after the update of reg_src. It is "stabilized" if
> + *    reg[shift] == size. If reg == NULL, this stable reg is not looked
> + *    up. Thus, in S5PV210, size is usually 0.
> + * @reg_div_stable: the register definition to probe if reg_div is
> + *    stabilized after the update of reg_div. Same mechanism with
> + *    reg_src_stable.
>   *
>   * This clock implements the features required by the newer SoCs where
>   * the standard clock block provides an input mux and a post-mux divisor
> @@ -61,6 +68,9 @@ struct clksrc_clk {
>  
>  	struct clksrc_reg	reg_src;
>  	struct clksrc_reg	reg_div;
> +
> +	struct clksrc_reg	reg_src_stable;
> +	struct clksrc_reg	reg_div_stable;
>  };
>  
>  /**