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->reg) {
+ 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;
+};
+
+/**
* 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;
};
/**
--
1.6.3.3
--
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