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@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> --
> v2:
> - Wait-for-stable loop is described at an inline function.
> v3:
> - Stop using clksrc_reg for stable bits. Use "clkstat_reg" for
> them.
>
> ---
> arch/arm/plat-samsung/clock-clksrc.c | 14 +++++++++++++
> arch/arm/plat-samsung/include/plat/clock-clksrc.h | 22
> +++++++++++++++++++++
> 2 files changed, 36 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/plat-samsung/clock-clksrc.c
b/arch/arm/plat-samsung/clock-
> clksrc.c
> index 46d204a..79ae92e 100644
> --- a/arch/arm/plat-samsung/clock-clksrc.c
> +++ b/arch/arm/plat-samsung/clock-clksrc.c
> @@ -50,6 +50,15 @@ static unsigned long s3c_getrate_clksrc(struct clk
*clk)
> return rate;
> }
>
> +static inline void s3c_wait_for_stable(struct clkstat_reg *stat)
> +{
> + WARN_ON(stat == NULL);
if (stat == NULL)
return;
If don't need to check status, have not become define relevant status
register.
> + if (stat->reg) {
No need?...or need to check stat->reg and stat->shift?
> + do { } while (((__raw_readl(stat->reg) >> stat->shift) & 1)
> + != stat->stable);
I'm still wondering we _really_ need 'stable'...just comments is enough,
right now.
> + do { } while (((__raw_readl(stat->reg) >> stat->shift) & 1)
> + != stat->stable);
> + }
> +}
> +
> static int s3c_setrate_clksrc(struct clk *clk, unsigned long rate)
> {
> struct clksrc_clk *sclk = to_clksrc(clk);
> @@ -68,6 +77,8 @@ static int s3c_setrate_clksrc(struct clk *clk, unsigned
long rate)
> val |= (div - 1) << sclk->reg_div.shift;
> __raw_writel(val, reg);
>
> + s3c_wait_for_stable(&sclk->reg_div_stable);
> +
> return 0;
> }
>
> @@ -93,6 +104,9 @@ 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);
> +
> + s3c_wait_for_stable(&sclk->reg_src_stable);
> +
> 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..f1d54da 100644
> --- a/arch/arm/plat-samsung/include/plat/clock-clksrc.h
> +++ b/arch/arm/plat-samsung/include/plat/clock-clksrc.h
> @@ -40,11 +40,30 @@ struct clksrc_reg {
> };
>
> /**
> + * struct clkstat_reg - register definition for clock stat bits
> + * @reg: pointer to the register in virtual memory.
> + * @shift: the shift in bits to where the bitfield is.
> + * @stable: the bit value of stable status.
> + */
> +struct clkstat_reg {
> + void __iomem *reg;
> + unsigned short shift;
> + unsigned short stable;
If you want to use this, just 'value' is better.
But...I think...we don't need this field now.
> +};
> +
> +/**
> * struct clksrc_clk - class of clock for newer style samsung devices.
> * @clk: the standard clock representation
> * @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 +80,9 @@ struct clksrc_clk {
>
> struct clksrc_reg reg_src;
> struct clksrc_reg reg_div;
> +
> + struct clkstat_reg reg_src_stable;
> + struct clkstat_reg reg_div_stable;
> };
>
> /**
> --
Thanks.
Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@xxxxxxxxxxx>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
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