[PATCH] cpufreq: scpi: compare against frequency instead of rate

[PATCH] cpufreq: scpi: compare against frequency instead of rate

[zuoqian]

The CPU rate from clk_get_rate() may not be divisible by 1000
(e.g., 133333333). But the rate calculated from frequency is always
divisible by 1000 (e.g., 133333000).
Comparing the rate causes a warning during CPU scaling:
"cpufreq: __target_index: Failed to change cpu frequency: -5".
When we choose to compare frequency here, the issue does not occur.

Signed-off-by: zuoqian <zuoqian113@gmail.com>
---
 drivers/cpufreq/scpi-cpufreq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
index cd89c1b9832c..3bff4bb5ab4a 100644
--- a/drivers/cpufreq/scpi-cpufreq.c
+++ b/drivers/cpufreq/scpi-cpufreq.c
@@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
 static int
 scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 {
-	u64 rate = policy->freq_table[index].frequency * 1000;
+	unsigned long freq = policy->freq_table[index].frequency;
 	struct scpi_data *priv = policy->driver_data;
+	u64 rate = freq * 1000;
 	int ret;
 
 	ret = clk_set_rate(priv->clk, rate);
@@ -48,7 +49,7 @@ scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 	if (ret)
 		return ret;
 
-	if (clk_get_rate(priv->clk) != rate)
+	if (clk_get_rate(priv->clk) / 1000 != freq)
 		return -EIO;
 
 	return 0;
-- 
2.43.0

Re: [PATCH] cpufreq: scpi: compare against frequency instead of rate

[Dan Carpenter]

On Thu, Jan 23, 2025 at 07:53:20AM +0000, zuoqian wrote:
> The CPU rate from clk_get_rate() may not be divisible by 1000
> (e.g., 133333333). But the rate calculated from frequency is always
> divisible by 1000 (e.g., 133333000).
> Comparing the rate causes a warning during CPU scaling:
> "cpufreq: __target_index: Failed to change cpu frequency: -5".
> When we choose to compare frequency here, the issue does not occur.
> 
> Signed-off-by: zuoqian <zuoqian113@gmail.com>
> ---
>  drivers/cpufreq/scpi-cpufreq.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
> index cd89c1b9832c..3bff4bb5ab4a 100644
> --- a/drivers/cpufreq/scpi-cpufreq.c
> +++ b/drivers/cpufreq/scpi-cpufreq.c
> @@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
>  static int
>  scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
>  {
> -	u64 rate = policy->freq_table[index].frequency * 1000;

policy->freq_table[index].frequency is a u32 so in this original
calculation, even though "rate" is declared as a u64, it can't actually
be more than UINT_MAX.

> +	unsigned long freq = policy->freq_table[index].frequency;
>  	struct scpi_data *priv = policy->driver_data;
> +	u64 rate = freq * 1000;

So you've fixed this by casting policy->freq_table[index].frequency
to unsigned long, which fixes the problem on 64bit systems but it still
remains on 32bit systems.  It would be better to declare freq as a u64.

We keep fixing and then breaking this as undocumented parts of larger
patches.  :P  It should really be done by itself and the Fixes tag would
point to:
Fixes: 1a0419b0db46 ("cpufreq: move invariance setter calls in cpufreq core")

>  	int ret;
>  
>  	ret = clk_set_rate(priv->clk, rate);
> @@ -48,7 +49,7 @@ scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
>  	if (ret)
>  		return ret;
>  
> -	if (clk_get_rate(priv->clk) != rate)
> +	if (clk_get_rate(priv->clk) / 1000 != freq)


Sure, I don't know this code well but your commit message seems reasonable.
Add a Fixes tag for this line.

Fixes: 343a8d17fa8d ("cpufreq: scpi: remove arm_big_little dependency")

regards,
dan carpenter

Re: [PATCH] cpufreq: scpi: compare against frequency instead of rate

[Sudeep Holla]

(for some reason I don't have the original email)

On Thu, Jan 23, 2025 at 02:12:14PM +0300, Dan Carpenter wrote:
> On Thu, Jan 23, 2025 at 07:53:20AM +0000, zuoqian wrote:
> > The CPU rate from clk_get_rate() may not be divisible by 1000
> > (e.g., 133333333). But the rate calculated from frequency is always
> > divisible by 1000 (e.g., 133333000).
> > Comparing the rate causes a warning during CPU scaling:
> > "cpufreq: __target_index: Failed to change cpu frequency: -5".
> > When we choose to compare frequency here, the issue does not occur.
> > 
> > Signed-off-by: zuoqian <zuoqian113@gmail.com>
> > ---
> >  drivers/cpufreq/scpi-cpufreq.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
> > index cd89c1b9832c..3bff4bb5ab4a 100644
> > --- a/drivers/cpufreq/scpi-cpufreq.c
> > +++ b/drivers/cpufreq/scpi-cpufreq.c
> > @@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
> >  static int
> >  scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
> >  {
> > -	u64 rate = policy->freq_table[index].frequency * 1000;
> 
> policy->freq_table[index].frequency is a u32 so in this original
> calculation, even though "rate" is declared as a u64, it can't actually
> be more than UINT_MAX.
>

Agreed and understood.

> > +	unsigned long freq = policy->freq_table[index].frequency;
> >  	struct scpi_data *priv = policy->driver_data;
> > +	u64 rate = freq * 1000;
>
> So you've fixed this by casting policy->freq_table[index].frequency
> to unsigned long, which fixes the problem on 64bit systems but it still
> remains on 32bit systems.  It would be better to declare freq as a u64.
>

Just trying to understand if that matters. freq is in kHz as copied
from policy->freq_table[index].frequency and we compare it with
kHZ below as the obtained clock rate is divided by 1000. What am I
missing ? If it helps, it can be renamed as freq_in_khz and even keep
it as "unsigned int" as in struct cpufreq_frequency_table.

-- 
Regards,
Sudeep

Re: [PATCH] cpufreq: scpi: compare against frequency instead of rate

[Dan Carpenter]

On Thu, Jan 23, 2025 at 12:16:50PM +0000, Sudeep Holla wrote:
> (for some reason I don't have the original email)
> 
> On Thu, Jan 23, 2025 at 02:12:14PM +0300, Dan Carpenter wrote:
> > On Thu, Jan 23, 2025 at 07:53:20AM +0000, zuoqian wrote:
> > > The CPU rate from clk_get_rate() may not be divisible by 1000
> > > (e.g., 133333333). But the rate calculated from frequency is always
> > > divisible by 1000 (e.g., 133333000).
> > > Comparing the rate causes a warning during CPU scaling:
> > > "cpufreq: __target_index: Failed to change cpu frequency: -5".
> > > When we choose to compare frequency here, the issue does not occur.
> > > 
> > > Signed-off-by: zuoqian <zuoqian113@gmail.com>
> > > ---
> > >  drivers/cpufreq/scpi-cpufreq.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
> > > index cd89c1b9832c..3bff4bb5ab4a 100644
> > > --- a/drivers/cpufreq/scpi-cpufreq.c
> > > +++ b/drivers/cpufreq/scpi-cpufreq.c
> > > @@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
> > >  static int
> > >  scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
> > >  {
> > > -	u64 rate = policy->freq_table[index].frequency * 1000;
> > 
> > policy->freq_table[index].frequency is a u32 so in this original
> > calculation, even though "rate" is declared as a u64, it can't actually
> > be more than UINT_MAX.
> >
> 
> Agreed and understood.
> 
> > > +	unsigned long freq = policy->freq_table[index].frequency;
> > >  	struct scpi_data *priv = policy->driver_data;
> > > +	u64 rate = freq * 1000;
> >
> > So you've fixed this by casting policy->freq_table[index].frequency
> > to unsigned long, which fixes the problem on 64bit systems but it still
> > remains on 32bit systems.  It would be better to declare freq as a u64.
> >
> 
> Just trying to understand if that matters. freq is in kHz as copied
> from policy->freq_table[index].frequency and we compare it with
> kHZ below as the obtained clock rate is divided by 1000. What am I
> missing ? If it helps, it can be renamed as freq_in_khz and even keep
> it as "unsigned int" as in struct cpufreq_frequency_table.
> 


I misunderstood the integer overflow bug because I read too much into the
fact that "rate" was declared as a u64.  It would have been fine to
declare it as a unsigned long.  The cpufreq internals don't support
anything more than ULONG_MAX.  I have heard someone say that new systems
are bumping up against the 4GHz limit but presumably that would only be
high end 64bit systems, not old 32bit system.

The ->freq_table[] frequency is in kHz so a u32 is fine.  I guess if we
get frequencies of a THz then we'll have to update that.  But when we
convert to Hz then we need a cast to avoid an integer overflow for systems
which are over the 4GHz boundary.

	unsigned long rate = (unsigned long)khz * 1000;

The second bug is that we need to compare kHz instead of Hz and that's
straight forward.

regards,
dan carpenter

Re: [PATCH] cpufreq: scpi: compare against frequency instead of rate

[zuoqian]

On Thu, Jan 23, 2025 at 04:04:13PM +0300, Dan Carpenter wrote:
> On Thu, Jan 23, 2025 at 12:16:50PM +0000, Sudeep Holla wrote:
> > (for some reason I don't have the original email)
> > 
> > On Thu, Jan 23, 2025 at 02:12:14PM +0300, Dan Carpenter wrote:
> > > On Thu, Jan 23, 2025 at 07:53:20AM +0000, zuoqian wrote:
> > > > The CPU rate from clk_get_rate() may not be divisible by 1000
> > > > (e.g., 133333333). But the rate calculated from frequency is always
> > > > divisible by 1000 (e.g., 133333000).
> > > > Comparing the rate causes a warning during CPU scaling:
> > > > "cpufreq: __target_index: Failed to change cpu frequency: -5".
> > > > When we choose to compare frequency here, the issue does not occur.
> > > > 
> > > > Signed-off-by: zuoqian <zuoqian113@gmail.com>
> > > > ---
> > > >  drivers/cpufreq/scpi-cpufreq.c | 5 +++--
> > > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
> > > > index cd89c1b9832c..3bff4bb5ab4a 100644
> > > > --- a/drivers/cpufreq/scpi-cpufreq.c
> > > > +++ b/drivers/cpufreq/scpi-cpufreq.c
> > > > @@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
> > > >  static int
> > > >  scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
> > > >  {
> > > > -	u64 rate = policy->freq_table[index].frequency * 1000;
> > > 
> > > policy->freq_table[index].frequency is a u32 so in this original
> > > calculation, even though "rate" is declared as a u64, it can't actually
> > > be more than UINT_MAX.
> > >
> > 
> > Agreed and understood.
> > 
> > > > +	unsigned long freq = policy->freq_table[index].frequency;
> > > >  	struct scpi_data *priv = policy->driver_data;
> > > > +	u64 rate = freq * 1000;
> > >
> > > So you've fixed this by casting policy->freq_table[index].frequency
> > > to unsigned long, which fixes the problem on 64bit systems but it still
> > > remains on 32bit systems.  It would be better to declare freq as a u64.
> > >
> > 
> > Just trying to understand if that matters. freq is in kHz as copied
> > from policy->freq_table[index].frequency and we compare it with
> > kHZ below as the obtained clock rate is divided by 1000. What am I
> > missing ? If it helps, it can be renamed as freq_in_khz and even keep
> > it as "unsigned int" as in struct cpufreq_frequency_table.
> > 
> 
> 
> I misunderstood the integer overflow bug because I read too much into the
> fact that "rate" was declared as a u64.  It would have been fine to
> declare it as a unsigned long.  The cpufreq internals don't support
> anything more than ULONG_MAX.  I have heard someone say that new systems
> are bumping up against the 4GHz limit but presumably that would only be
> high end 64bit systems, not old 32bit system.
> 
> The ->freq_table[] frequency is in kHz so a u32 is fine.  I guess if we
> get frequencies of a THz then we'll have to update that.  But when we
> convert to Hz then we need a cast to avoid an integer overflow for systems
> which are over the 4GHz boundary.
> 
> 	unsigned long rate = (unsigned long)khz * 1000;
> 
> The second bug is that we need to compare kHz instead of Hz and that's
> straight forward.
> 
> regards,
> dan carpenter
>

Thank you for your valuable feedback.I will make the changes to the patch and 
resubmit it, including renaming freq and keeping it as an "unsigned int".

Regards,
Zuoqian

Re: [PATCH] cpufreq: scpi: compare against frequency instead of rate

[Dan Carpenter]

On Fri, Jan 24, 2025 at 09:42:01AM +0000, zuoqian wrote:
> On Thu, Jan 23, 2025 at 04:04:13PM +0300, Dan Carpenter wrote:
> > On Thu, Jan 23, 2025 at 12:16:50PM +0000, Sudeep Holla wrote:
> > > (for some reason I don't have the original email)
> > > 
> > > On Thu, Jan 23, 2025 at 02:12:14PM +0300, Dan Carpenter wrote:
> > > > On Thu, Jan 23, 2025 at 07:53:20AM +0000, zuoqian wrote:
> > > > > The CPU rate from clk_get_rate() may not be divisible by 1000
> > > > > (e.g., 133333333). But the rate calculated from frequency is always
> > > > > divisible by 1000 (e.g., 133333000).
> > > > > Comparing the rate causes a warning during CPU scaling:
> > > > > "cpufreq: __target_index: Failed to change cpu frequency: -5".
> > > > > When we choose to compare frequency here, the issue does not occur.
> > > > > 
> > > > > Signed-off-by: zuoqian <zuoqian113@gmail.com>
> > > > > ---
> > > > >  drivers/cpufreq/scpi-cpufreq.c | 5 +++--
> > > > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
> > > > > index cd89c1b9832c..3bff4bb5ab4a 100644
> > > > > --- a/drivers/cpufreq/scpi-cpufreq.c
> > > > > +++ b/drivers/cpufreq/scpi-cpufreq.c
> > > > > @@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
> > > > >  static int
> > > > >  scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
> > > > >  {
> > > > > -	u64 rate = policy->freq_table[index].frequency * 1000;
> > > > 
> > > > policy->freq_table[index].frequency is a u32 so in this original
> > > > calculation, even though "rate" is declared as a u64, it can't actually
> > > > be more than UINT_MAX.
> > > >
> > > 
> > > Agreed and understood.
> > > 
> > > > > +	unsigned long freq = policy->freq_table[index].frequency;
> > > > >  	struct scpi_data *priv = policy->driver_data;
> > > > > +	u64 rate = freq * 1000;
> > > >
> > > > So you've fixed this by casting policy->freq_table[index].frequency
> > > > to unsigned long, which fixes the problem on 64bit systems but it still
> > > > remains on 32bit systems.  It would be better to declare freq as a u64.
> > > >
> > > 
> > > Just trying to understand if that matters. freq is in kHz as copied
> > > from policy->freq_table[index].frequency and we compare it with
> > > kHZ below as the obtained clock rate is divided by 1000. What am I
> > > missing ? If it helps, it can be renamed as freq_in_khz and even keep
> > > it as "unsigned int" as in struct cpufreq_frequency_table.
> > > 
> > 
> > 
> > I misunderstood the integer overflow bug because I read too much into the
> > fact that "rate" was declared as a u64.  It would have been fine to
> > declare it as a unsigned long.  The cpufreq internals don't support
> > anything more than ULONG_MAX.  I have heard someone say that new systems
> > are bumping up against the 4GHz limit but presumably that would only be
> > high end 64bit systems, not old 32bit system.
> > 
> > The ->freq_table[] frequency is in kHz so a u32 is fine.  I guess if we
> > get frequencies of a THz then we'll have to update that.  But when we
> > convert to Hz then we need a cast to avoid an integer overflow for systems
> > which are over the 4GHz boundary.
> > 
> > 	unsigned long rate = (unsigned long)khz * 1000;
> > 
> > The second bug is that we need to compare kHz instead of Hz and that's
> > straight forward.
> > 
> > regards,
> > dan carpenter
> >
> 
> Thank you for your valuable feedback.I will make the changes to the patch and 
> resubmit it, including renaming freq and keeping it as an "unsigned int".

If you keep it as unsigned int then you will need to add a cast when you
do the "* 1000" multiplication.  Please make freq and rate both unsigned
longs.

regards,
dan carpenter

[PATCH v2] cpufreq: scpi: compare kHz instead of Hz

[zuoqian]

The CPU rate from clk_get_rate() may not be divisible by 1000
(e.g., 133333333). But the rate calculated from frequency(kHz) is
always divisible by 1000 (e.g., 133333000).
Comparing the rate causes a warning during CPU scaling:
"cpufreq: __target_index: Failed to change cpu frequency: -5".
When we choose to compare kHz here, the issue does not occur.

Fixes: 343a8d17fa8d ("cpufreq: scpi: remove arm_big_little dependency")
Signed-off-by: zuoqian <zuoqian113@gmail.com>
---
V1 -> V2: rename freq to freq_khz, change rate to unsigned long, and
update patch summary.
---
 drivers/cpufreq/scpi-cpufreq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
index cd89c1b9832c..9e09565e41c0 100644
--- a/drivers/cpufreq/scpi-cpufreq.c
+++ b/drivers/cpufreq/scpi-cpufreq.c
@@ -39,8 +39,9 @@ static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
 static int
 scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 {
-	u64 rate = policy->freq_table[index].frequency * 1000;
+	unsigned long freq_khz = policy->freq_table[index].frequency;
 	struct scpi_data *priv = policy->driver_data;
+	unsigned long rate = freq_khz * 1000;
 	int ret;
 
 	ret = clk_set_rate(priv->clk, rate);
@@ -48,7 +49,7 @@ scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 	if (ret)
 		return ret;
 
-	if (clk_get_rate(priv->clk) != rate)
+	if (clk_get_rate(priv->clk) / 1000 != freq_khz)
 		return -EIO;
 
 	return 0;
-- 
2.43.0

Re: [PATCH v2] cpufreq: scpi: compare kHz instead of Hz

[Dan Carpenter]

On Sat, Jan 25, 2025 at 08:49:49AM +0000, zuoqian wrote:
> The CPU rate from clk_get_rate() may not be divisible by 1000
> (e.g., 133333333). But the rate calculated from frequency(kHz) is
> always divisible by 1000 (e.g., 133333000).
> Comparing the rate causes a warning during CPU scaling:
> "cpufreq: __target_index: Failed to change cpu frequency: -5".
> When we choose to compare kHz here, the issue does not occur.
> 
> Fixes: 343a8d17fa8d ("cpufreq: scpi: remove arm_big_little dependency")
> Signed-off-by: zuoqian <zuoqian113@gmail.com>
> ---
> V1 -> V2: rename freq to freq_khz, change rate to unsigned long, and
> update patch summary.

Thanks!

Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>

regards,
dan carpenter

Re: [PATCH v2] cpufreq: scpi: compare kHz instead of Hz

[Viresh Kumar]

On 25-01-25, 16:04, Dan Carpenter wrote:
> On Sat, Jan 25, 2025 at 08:49:49AM +0000, zuoqian wrote:
> > The CPU rate from clk_get_rate() may not be divisible by 1000
> > (e.g., 133333333). But the rate calculated from frequency(kHz) is
> > always divisible by 1000 (e.g., 133333000).
> > Comparing the rate causes a warning during CPU scaling:
> > "cpufreq: __target_index: Failed to change cpu frequency: -5".
> > When we choose to compare kHz here, the issue does not occur.
> > 
> > Fixes: 343a8d17fa8d ("cpufreq: scpi: remove arm_big_little dependency")
> > Signed-off-by: zuoqian <zuoqian113@gmail.com>
> > ---
> > V1 -> V2: rename freq to freq_khz, change rate to unsigned long, and
> > update patch summary.
> 
> Thanks!
> 
> Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>

Applied. Thanks.

-- 
viresh

Re: [PATCH v2] cpufreq: scpi: compare kHz instead of Hz

[Dan Carpenter]

On Sat, Jan 25, 2025 at 08:49:49AM +0000, zuoqian wrote:
> The CPU rate from clk_get_rate() may not be divisible by 1000
> (e.g., 133333333). But the rate calculated from frequency(kHz) is
> always divisible by 1000 (e.g., 133333000).
> Comparing the rate causes a warning during CPU scaling:
> "cpufreq: __target_index: Failed to change cpu frequency: -5".
> When we choose to compare kHz here, the issue does not occur.
> 
> Fixes: 343a8d17fa8d ("cpufreq: scpi: remove arm_big_little dependency")
> Signed-off-by: zuoqian <zuoqian113@gmail.com>
> ---
> V1 -> V2: rename freq to freq_khz, change rate to unsigned long, and
> update patch summary.

Thanks!

Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>

regards,
dan carpenter