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SubjectRe: [PATCH] cpufreq: set value of CPUFREQ_BOOST_FREQ to 0xABABABAB
Hi Viresh,

> Ideally, .driver_data field of struct cpufreq_frequency_table must
> not be used by core at all. But during a recent change if its value
> is same as CPUFREQ_BOOST_FREQ macro, then it is treated specially by
> core.
>
> The value of this macro was set to ~2 earlier, i.e. 0xFFFFFFFD. In
> case some driver is using this field for its own data and sets this
> field to -3, then with two's complement that value will also become
> 0xFFFFFFFD.
>
> To fix this issue, lets change value of this flag to a very uncommon
> value which shouldn't be used by any driver unless they want to use
> BOOST feature.
>
> Along with this update comments to make this more clear.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>
> Gautham/Vaidy: I hope this fixes the problem we discussed for your
> patchset.
>

I think that a name of the patchset, for which the current setting
causes problem would be welcome here.

Otherwise, I can only ask why it is not possible to add
#define SPECIAL_SETTING ~3 ?


> include/linux/cpufreq.h | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index c48e595..9f25d9d 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -455,12 +455,18 @@ extern struct cpufreq_governor
> cpufreq_gov_conservative;
> * FREQUENCY TABLE HELPERS
> *
> *********************************************************************/
> +/* Special Values of .frequency field */
> #define CPUFREQ_ENTRY_INVALID ~0
> #define CPUFREQ_TABLE_END ~1
> -#define CPUFREQ_BOOST_FREQ ~2
> +/* Special Values of .driver_data field */
> +#define CPUFREQ_BOOST_FREQ 0xABABABAB
>
> struct cpufreq_frequency_table {
> - unsigned int driver_data; /* driver specific data,
> not used by core */
> + /*
> + * driver specific data, not used by core unless it is set to
> + * CPUFREQ_BOOST_FREQ.
> + */
> + unsigned int driver_data;
> unsigned int frequency; /* kHz - doesn't need to be
> in ascending
> * order */
> };



--
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group


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