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From: Hans de Goede <hdegoede@redhat.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Colin Ian King <colin.king@canonical.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Mark Gross <mgross@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Jesse Barnes <jsbarnes@google.com>
Cc: platform-driver-x86@vger.kernel.org,
	intel-gfx@lists.freedesktop.org,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c
Date: Thu, 10 Jun 2021 17:55:19 +0200	[thread overview]
Message-ID: <7e13032d-1472-9c50-1dba-9dcebc76729f@redhat.com> (raw)
In-Reply-To: <162332615476.15946.17135355064135638083@jlahtine-mobl.ger.corp.intel.com>

Hi,

On 6/10/21 1:55 PM, Joonas Lahtinen wrote:
> (Address for Hans was corrupt in previous message, which confused my mail
> client. Sorry for duplicate message, the other is without From: field).
> 
> + Jesse
> 
> Quoting Colin Ian King (2021-06-09 14:50:07)
>> Hi,
>>
>> I was reviewing some old unassigned variable warnings from static
>> analysis by Coverity and found an issue introduced with the following
>> commit:
>>
>> commit aa7ffc01d254c91a36bf854d57a14049c6134c72
>> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
>> Date:   Fri May 14 15:41:14 2010 -0700
>>
>>     x86 platform driver: intelligent power sharing driver
>>
>> The analysis is as follows:
>>
>> drivers/platform/x86/intel_ips.c
>>
>>  871 static u32 get_cpu_power(struct ips_driver *ips, u32 *last, int period)
>>  872 {
>>  873        u32 val;
>>  874        u32 ret;
>>  875
>>  876        /*
>>  877         * CEC is in joules/65535.  Take difference over time to
>>  878         * get watts.
>>  879         */
>>  880        val = thm_readl(THM_CEC);
>>  881
>>  882        /* period is in ms and we want mW */
>>  883        ret = (((val - *last) * 1000) / period);
>>
>> Unused value (UNUSED_VALUE)
>> assigned_value:  Assigning value from ret * 1000U / 65535U to ret here,
>> but that stored value is not used.
>>
>>  884        ret = (ret * 1000) / 65535;
>>  885        *last = val;
>>  886
>>  887        return 0;
>>  888 }
>>
>> I'm really not sure why ret is being calculated on lines 883,884 and not
>> being used. Should that be *last = ret on line 885? Looks suspect anyhow.

This has already been fixed (yesterday actually) in linux-next:

https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=13c3b4f76073d73dd81e418295902676153f6cb5

Regards,

Hans


WARNING: multiple messages have this Message-ID (diff)
From: Hans de Goede <hdegoede@redhat.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Colin Ian King <colin.king@canonical.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Mark Gross <mgross@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Jesse Barnes <jsbarnes@google.com>
Cc: intel-gfx@lists.freedesktop.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	platform-driver-x86@vger.kernel.org
Subject: Re: Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c
Date: Thu, 10 Jun 2021 17:55:19 +0200	[thread overview]
Message-ID: <7e13032d-1472-9c50-1dba-9dcebc76729f@redhat.com> (raw)
In-Reply-To: <162332615476.15946.17135355064135638083@jlahtine-mobl.ger.corp.intel.com>

Hi,

On 6/10/21 1:55 PM, Joonas Lahtinen wrote:
> (Address for Hans was corrupt in previous message, which confused my mail
> client. Sorry for duplicate message, the other is without From: field).
> 
> + Jesse
> 
> Quoting Colin Ian King (2021-06-09 14:50:07)
>> Hi,
>>
>> I was reviewing some old unassigned variable warnings from static
>> analysis by Coverity and found an issue introduced with the following
>> commit:
>>
>> commit aa7ffc01d254c91a36bf854d57a14049c6134c72
>> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
>> Date:   Fri May 14 15:41:14 2010 -0700
>>
>>     x86 platform driver: intelligent power sharing driver
>>
>> The analysis is as follows:
>>
>> drivers/platform/x86/intel_ips.c
>>
>>  871 static u32 get_cpu_power(struct ips_driver *ips, u32 *last, int period)
>>  872 {
>>  873        u32 val;
>>  874        u32 ret;
>>  875
>>  876        /*
>>  877         * CEC is in joules/65535.  Take difference over time to
>>  878         * get watts.
>>  879         */
>>  880        val = thm_readl(THM_CEC);
>>  881
>>  882        /* period is in ms and we want mW */
>>  883        ret = (((val - *last) * 1000) / period);
>>
>> Unused value (UNUSED_VALUE)
>> assigned_value:  Assigning value from ret * 1000U / 65535U to ret here,
>> but that stored value is not used.
>>
>>  884        ret = (ret * 1000) / 65535;
>>  885        *last = val;
>>  886
>>  887        return 0;
>>  888 }
>>
>> I'm really not sure why ret is being calculated on lines 883,884 and not
>> being used. Should that be *last = ret on line 885? Looks suspect anyhow.

This has already been fixed (yesterday actually) in linux-next:

https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=13c3b4f76073d73dd81e418295902676153f6cb5

Regards,

Hans


WARNING: multiple messages have this Message-ID (diff)
From: Hans de Goede <hdegoede@redhat.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Colin Ian King <colin.king@canonical.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Mark Gross <mgross@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Jesse Barnes <jsbarnes@google.com>
Cc: intel-gfx@lists.freedesktop.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	platform-driver-x86@vger.kernel.org
Subject: Re: [Intel-gfx] Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c
Date: Thu, 10 Jun 2021 17:55:19 +0200	[thread overview]
Message-ID: <7e13032d-1472-9c50-1dba-9dcebc76729f@redhat.com> (raw)
In-Reply-To: <162332615476.15946.17135355064135638083@jlahtine-mobl.ger.corp.intel.com>

Hi,

On 6/10/21 1:55 PM, Joonas Lahtinen wrote:
> (Address for Hans was corrupt in previous message, which confused my mail
> client. Sorry for duplicate message, the other is without From: field).
> 
> + Jesse
> 
> Quoting Colin Ian King (2021-06-09 14:50:07)
>> Hi,
>>
>> I was reviewing some old unassigned variable warnings from static
>> analysis by Coverity and found an issue introduced with the following
>> commit:
>>
>> commit aa7ffc01d254c91a36bf854d57a14049c6134c72
>> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
>> Date:   Fri May 14 15:41:14 2010 -0700
>>
>>     x86 platform driver: intelligent power sharing driver
>>
>> The analysis is as follows:
>>
>> drivers/platform/x86/intel_ips.c
>>
>>  871 static u32 get_cpu_power(struct ips_driver *ips, u32 *last, int period)
>>  872 {
>>  873        u32 val;
>>  874        u32 ret;
>>  875
>>  876        /*
>>  877         * CEC is in joules/65535.  Take difference over time to
>>  878         * get watts.
>>  879         */
>>  880        val = thm_readl(THM_CEC);
>>  881
>>  882        /* period is in ms and we want mW */
>>  883        ret = (((val - *last) * 1000) / period);
>>
>> Unused value (UNUSED_VALUE)
>> assigned_value:  Assigning value from ret * 1000U / 65535U to ret here,
>> but that stored value is not used.
>>
>>  884        ret = (ret * 1000) / 65535;
>>  885        *last = val;
>>  886
>>  887        return 0;
>>  888 }
>>
>> I'm really not sure why ret is being calculated on lines 883,884 and not
>> being used. Should that be *last = ret on line 885? Looks suspect anyhow.

This has already been fixed (yesterday actually) in linux-next:

https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=13c3b4f76073d73dd81e418295902676153f6cb5

Regards,

Hans

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  parent reply	other threads:[~2021-06-10 15:55 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-09 11:50 Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c Colin Ian King
2021-06-09 11:50 ` [Intel-gfx] " Colin Ian King
2021-06-09 11:50 ` Colin Ian King
2021-06-10 11:51 ` joonas.lahtinen
2021-06-10 11:51   ` [Intel-gfx] " joonas.lahtinen
2021-06-10 11:51   ` joonas.lahtinen
2021-06-10 11:55 ` Joonas Lahtinen
2021-06-10 11:55   ` [Intel-gfx] " Joonas Lahtinen
2021-06-10 11:55   ` Joonas Lahtinen
2021-06-10 15:40   ` Jesse Barnes
2021-06-10 15:40     ` [Intel-gfx] " Jesse Barnes
2021-06-10 15:43   ` Jesse Barnes
2021-06-10 15:43     ` [Intel-gfx] " Jesse Barnes
2021-06-10 15:43     ` Jesse Barnes
2021-06-10 15:55   ` Hans de Goede [this message]
2021-06-10 15:55     ` [Intel-gfx] " Hans de Goede
2021-06-10 15:55     ` Hans de Goede

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