Patches are self-explanatory I think. So, just changelog is provided here.
It would be really nice to queue them to v4.1.
Patches 2/3 and 3/3 are dependent to the patch 1/7 from [1] "clk: replace
div_mask() by clk_div_mask()".
The series was tested with 8250_dw UART driver on Intel Braswell.
[1] http://www.spinics.net/lists/kernel/msg1958958.html
Changelog v3:
- add patch 2/3 to simplify further usage
- don't use mult_frac() due to potential overflow on 32 bit kernels
- guarantee in ->round_rate() that m and n will not overflow
Changelog v2:
- move to rational_best_approximation() and mult_frac()
- add patch 2/2
Andy Shevchenko (3):
clk: fractional-divider: fix sparse warnings
clk: fractional-divider: keep mwidth and nwidth internally
clk: fractional-divider: switch to rational best approximation
drivers/clk/Kconfig | 1 +
drivers/clk/clk-fractional-divider.c | 86 +++++++++++++++++++++---------------
include/linux/clk-provider.h | 3 +-
3 files changed, 54 insertions(+), 36 deletions(-)
--
2.1.4
Sparse complains about possible imbalance in locking.
drivers/clk/clk-fractional-divider.c:37:9: warning: context imbalance in 'clk_fd_recalc_rate' - different lock contexts for basic block
drivers/clk/clk-fractional-divider.c:61:12: warning: context imbalance in 'clk_fd_set_rate' - different lock contexts for basic block
Let's rewrite code to fix this and make it more straight.
Signed-off-by: Andy Shevchenko <[email protected]>
---
drivers/clk/clk-fractional-divider.c | 44 +++++++++++++++++++++---------------
1 file changed, 26 insertions(+), 18 deletions(-)
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index 6aa72d9..786aa482 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -21,17 +21,18 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
- unsigned long flags = 0;
- u32 val, m, n;
+ unsigned long flags;
+ unsigned long m, n;
+ u32 val;
u64 ret;
- if (fd->lock)
+ if (fd->lock) {
spin_lock_irqsave(fd->lock, flags);
-
- val = clk_readl(fd->reg);
-
- if (fd->lock)
+ val = clk_readl(fd->reg);
spin_unlock_irqrestore(fd->lock, flags);
+ } else {
+ val = clk_readl(fd->reg);
+ }
m = (val & fd->mmask) >> fd->mshift;
n = (val & fd->nmask) >> fd->nshift;
@@ -65,29 +66,36 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
return rate;
}
+static void clk_fd_update(struct clk_fractional_divider *fd,
+ unsigned long m, unsigned long n)
+{
+ u32 val;
+
+ val = clk_readl(fd->reg);
+ val &= ~(fd->mmask | fd->nmask);
+ val |= (m << fd->mshift) | (n << fd->nshift);
+ clk_writel(val, fd->reg);
+}
+
static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
- unsigned long flags = 0;
+ unsigned long flags;
unsigned long div;
- unsigned n, m;
- u32 val;
+ unsigned long m, n;
div = gcd(parent_rate, rate);
m = rate / div;
n = parent_rate / div;
- if (fd->lock)
+ if (fd->lock) {
spin_lock_irqsave(fd->lock, flags);
-
- val = clk_readl(fd->reg);
- val &= ~(fd->mmask | fd->nmask);
- val |= (m << fd->mshift) | (n << fd->nshift);
- clk_writel(val, fd->reg);
-
- if (fd->lock)
+ clk_fd_update(fd, m, n);
spin_unlock_irqrestore(fd->lock, flags);
+ } else {
+ clk_fd_update(fd, m, n);
+ }
return 0;
}
--
2.1.4
The patch adds mwidth and nwidth fields to the struct clk_fractional_divider
for further usage. While here, use clk_div_mask() instead of open coding this
functionality.
Signed-off-by: Andy Shevchenko <[email protected]>
---
drivers/clk/clk-fractional-divider.c | 8 +++++---
include/linux/clk-provider.h | 3 ++-
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index 786aa482..23a56a0 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -50,7 +50,7 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
- unsigned maxn = (fd->nmask >> fd->nshift) + 1;
+ unsigned maxn = clk_div_mask(fd->nwidth) + 1;
unsigned div;
if (!rate || rate >= *prate)
@@ -130,9 +130,11 @@ struct clk *clk_register_fractional_divider(struct device *dev,
fd->reg = reg;
fd->mshift = mshift;
- fd->mmask = (BIT(mwidth) - 1) << mshift;
+ fd->mwidth = mwidth;
+ fd->mmask = clk_div_mask(mwidth) << mshift;
fd->nshift = nshift;
- fd->nmask = (BIT(nwidth) - 1) << nshift;
+ fd->nwidth = nwidth;
+ fd->nmask = clk_div_mask(nwidth) << nshift;
fd->flags = clk_divider_flags;
fd->lock = lock;
fd->hw.init = &init;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 20b0b67..eb3c96f 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -480,13 +480,14 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
*
* Clock with adjustable fractional divider affecting its output frequency.
*/
-
struct clk_fractional_divider {
struct clk_hw hw;
void __iomem *reg;
u8 mshift;
+ u8 mwidth;
u32 mmask;
u8 nshift;
+ u8 nwidth;
u32 nmask;
u8 flags;
spinlock_t *lock;
--
2.1.4
This patch converts the code to use rational best approximation algorithm which
is more precise.
Suggested-by: Stephen Boyd <[email protected]>
Signed-off-by: Andy Shevchenko <[email protected]>
---
drivers/clk/Kconfig | 1 +
drivers/clk/clk-fractional-divider.c | 38 +++++++++++++++++++++---------------
2 files changed, 23 insertions(+), 16 deletions(-)
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 0b474a0..3a1b1dc 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -14,6 +14,7 @@ config COMMON_CLK
select HAVE_CLK_PREPARE
select CLKDEV_LOOKUP
select SRCU
+ select RATIONAL
---help---
The common clock framework is a single definition of struct
clk, useful across many platforms, as well as an
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index 23a56a0..f060be8 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -7,13 +7,14 @@
*
* Adjustable fractional divider clock implementation.
* Output rate = (m / n) * parent_rate.
+ * Uses rational best approximation algorithm.
*/
#include <linux/clk-provider.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/slab.h>
-#include <linux/gcd.h>
+#include <linux/rational.h>
#define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, hw)
@@ -47,23 +48,29 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
}
static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
- unsigned long *prate)
+ unsigned long *parent_rate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
- unsigned maxn = clk_div_mask(fd->nwidth) + 1;
- unsigned div;
+ unsigned long scale;
+ unsigned long m, n;
+ u64 ret;
- if (!rate || rate >= *prate)
- return *prate;
+ if (!rate || rate >= *parent_rate)
+ return *parent_rate;
- div = gcd(*prate, rate);
+ /* Get rate closer to *parent_rate */
+ scale = fls_long(*parent_rate / rate - 1);
+ if (scale > fd->nwidth)
+ rate <<= scale - fd->nwidth;
- while ((*prate / div) > maxn) {
- div <<= 1;
- rate <<= 1;
- }
+ rational_best_approximation(rate, *parent_rate,
+ clk_div_mask(fd->mwidth), clk_div_mask(fd->nwidth),
+ &m, &n);
- return rate;
+ ret = (u64)*parent_rate * m;
+ do_div(ret, n);
+
+ return ret;
}
static void clk_fd_update(struct clk_fractional_divider *fd,
@@ -82,12 +89,11 @@ static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
unsigned long flags;
- unsigned long div;
unsigned long m, n;
- div = gcd(parent_rate, rate);
- m = rate / div;
- n = parent_rate / div;
+ rational_best_approximation(rate, parent_rate,
+ clk_div_mask(fd->mwidth), clk_div_mask(fd->nwidth),
+ &m, &n);
if (fd->lock) {
spin_lock_irqsave(fd->lock, flags);
--
2.1.4
On Wed, Apr 1, 2015 at 6:09 PM, Andy Shevchenko
<[email protected]> wrote:
> The patch adds mwidth and nwidth fields to the struct clk_fractional_divider
> for further usage. While here, use clk_div_mask() instead of open coding this
> functionality.
>
> Signed-off-by: Andy Shevchenko <[email protected]>
> ---
> drivers/clk/clk-fractional-divider.c | 8 +++++---
> include/linux/clk-provider.h | 3 ++-
> 2 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> index 786aa482..23a56a0 100644
> --- a/drivers/clk/clk-fractional-divider.c
> +++ b/drivers/clk/clk-fractional-divider.c
> @@ -50,7 +50,7 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
> unsigned long *prate)
> {
> struct clk_fractional_divider *fd = to_clk_fd(hw);
> - unsigned maxn = (fd->nmask >> fd->nshift) + 1;
> + unsigned maxn = clk_div_mask(fd->nwidth) + 1;
Looks clk_div_mask() can't be found when I build the latest
next with these 3 patches:
CC drivers/clk/clk-fractional-divider.o
drivers/clk/clk-fractional-divider.c: In function ‘clk_fd_round_rate’:
drivers/clk/clk-fractional-divider.c:67:4: error: implicit declaration
of function ‘clk_div_mask’ [-Werror=implicit-function-declaration]
clk_div_mask(fd->mwidth), clk_div_mask(fd->nwidth),
^
cc1: some warnings being treated as errors
make[2]: *** [drivers/clk/clk-fractional-divider.o] Error 1
Thanks,
> unsigned div;
>
> if (!rate || rate >= *prate)
> @@ -130,9 +130,11 @@ struct clk *clk_register_fractional_divider(struct device *dev,
>
> fd->reg = reg;
> fd->mshift = mshift;
> - fd->mmask = (BIT(mwidth) - 1) << mshift;
> + fd->mwidth = mwidth;
> + fd->mmask = clk_div_mask(mwidth) << mshift;
> fd->nshift = nshift;
> - fd->nmask = (BIT(nwidth) - 1) << nshift;
> + fd->nwidth = nwidth;
> + fd->nmask = clk_div_mask(nwidth) << nshift;
> fd->flags = clk_divider_flags;
> fd->lock = lock;
> fd->hw.init = &init;
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 20b0b67..eb3c96f 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -480,13 +480,14 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
> *
> * Clock with adjustable fractional divider affecting its output frequency.
> */
> -
> struct clk_fractional_divider {
> struct clk_hw hw;
> void __iomem *reg;
> u8 mshift;
> + u8 mwidth;
> u32 mmask;
> u8 nshift;
> + u8 nwidth;
> u32 nmask;
> u8 flags;
> spinlock_t *lock;
> --
> 2.1.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Ming Lei
On Thu, 2015-04-09 at 16:22 +0800, Ming Lei wrote:
> On Wed, Apr 1, 2015 at 6:09 PM, Andy Shevchenko
> <[email protected]> wrote:
> > The patch adds mwidth and nwidth fields to the struct clk_fractional_divider
> > for further usage. While here, use clk_div_mask() instead of open coding this
> > functionality.
> >
> > Signed-off-by: Andy Shevchenko <[email protected]>
> > ---
> > drivers/clk/clk-fractional-divider.c | 8 +++++---
> > include/linux/clk-provider.h | 3 ++-
> > 2 files changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> > index 786aa482..23a56a0 100644
> > --- a/drivers/clk/clk-fractional-divider.c
> > +++ b/drivers/clk/clk-fractional-divider.c
> > @@ -50,7 +50,7 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
> > unsigned long *prate)
> > {
> > struct clk_fractional_divider *fd = to_clk_fd(hw);
> > - unsigned maxn = (fd->nmask >> fd->nshift) + 1;
> > + unsigned maxn = clk_div_mask(fd->nwidth) + 1;
>
> Looks clk_div_mask() can't be found when I build the latest
> next with these 3 patches:
And you have read cover letter carefully, right?
It mentions that you have to apply at least one patch from the other
series: http://www.spinics.net/lists/kernel/msg1958958.html
>
> CC drivers/clk/clk-fractional-divider.o
> drivers/clk/clk-fractional-divider.c: In function ‘clk_fd_round_rate’:
> drivers/clk/clk-fractional-divider.c:67:4: error: implicit declaration
> of function ‘clk_div_mask’ [-Werror=implicit-function-declaration]
> clk_div_mask(fd->mwidth), clk_div_mask(fd->nwidth),
> ^
> cc1: some warnings being treated as errors
> make[2]: *** [drivers/clk/clk-fractional-divider.o] Error 1
>
> Thanks,
>
> > unsigned div;
> >
> > if (!rate || rate >= *prate)
> > @@ -130,9 +130,11 @@ struct clk *clk_register_fractional_divider(struct device *dev,
> >
> > fd->reg = reg;
> > fd->mshift = mshift;
> > - fd->mmask = (BIT(mwidth) - 1) << mshift;
> > + fd->mwidth = mwidth;
> > + fd->mmask = clk_div_mask(mwidth) << mshift;
> > fd->nshift = nshift;
> > - fd->nmask = (BIT(nwidth) - 1) << nshift;
> > + fd->nwidth = nwidth;
> > + fd->nmask = clk_div_mask(nwidth) << nshift;
> > fd->flags = clk_divider_flags;
> > fd->lock = lock;
> > fd->hw.init = &init;
> > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> > index 20b0b67..eb3c96f 100644
> > --- a/include/linux/clk-provider.h
> > +++ b/include/linux/clk-provider.h
> > @@ -480,13 +480,14 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
> > *
> > * Clock with adjustable fractional divider affecting its output frequency.
> > */
> > -
> > struct clk_fractional_divider {
> > struct clk_hw hw;
> > void __iomem *reg;
> > u8 mshift;
> > + u8 mwidth;
> > u32 mmask;
> > u8 nshift;
> > + u8 nwidth;
> > u32 nmask;
> > u8 flags;
> > spinlock_t *lock;
> > --
> > 2.1.4
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
>
>
>
--
Andy Shevchenko <[email protected]>
Intel Finland Oy
On 04/01, Andy Shevchenko wrote:
> Patches are self-explanatory I think. So, just changelog is provided here.
> It would be really nice to queue them to v4.1.
>
> Patches 2/3 and 3/3 are dependent to the patch 1/7 from [1] "clk: replace
> div_mask() by clk_div_mask()".
>
> The series was tested with 8250_dw UART driver on Intel Braswell.
>
Please undo the dependency of this series on clk_div_mask and
then it can be applied, targeting 4.3.
--
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