[bug report] powercap: arm_scmi: Add SCMI powercap based driver

[bug report] powercap: arm_scmi: Add SCMI powercap based driver

[Dan Carpenter]

Hello Cristian Marussi,

The patch 31afdd34f2b9: "powercap: arm_scmi: Add SCMI powercap based
driver" from Jul 4, 2022, leads to the following Smatch static
checker warning:

	drivers/powercap/arm_scmi_powercap.c:214 scmi_powercap_get_max_power_uw()
	warn: cast after binop

drivers/powercap/arm_scmi_powercap.c
   203  static int scmi_powercap_get_max_power_uw(struct powercap_zone *pz, int cid,
   204                                            u64 *max_power_uw)
   205  {
   206          struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
   207  
   208          if (!spz->info)
   209                  return -ENODEV;
   210  
   211          if (spz->info->powercap_scale_uw)
   212                  *max_power_uw = (u64)spz->info->max_power_cap;
   213          else
   214                  *max_power_uw = (u64)(spz->info->max_power_cap * 1000);

What's the deal with this cast?  It would make more sense to do the cast
before the * 1000 so that it doesn't overflow the 32 bits.  Is the cast
even required though?  The cast on the line before is decorative so
maybe it's not required.

   215  
   216          return 0;
   217  }
   218  
   219  static int scmi_powercap_get_min_power_uw(struct powercap_zone *pz, int cid,
   220                                            u64 *min_power_uw)
   221  {
   222          struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
   223  
   224          if (!spz->info)
   225                  return -ENODEV;
   226  
   227          if (spz->info->powercap_scale_uw)
   228                  *min_power_uw = (u64)spz->info->min_power_cap;
   229          else
   230                  *min_power_uw = (u64)(spz->info->min_power_cap * 1000);

Same cast here.

   231  
   232          return 0;
   233  }

regards,
dan carpenter

Re: [bug report] powercap: arm_scmi: Add SCMI powercap based driver

[Cristian Marussi]

On Wed, Jul 06, 2022 at 05:09:13PM +0300, Dan Carpenter wrote:
> Hello Cristian Marussi,
> 

Hi Dan Carpenter,

> The patch 31afdd34f2b9: "powercap: arm_scmi: Add SCMI powercap based
> driver" from Jul 4, 2022, leads to the following Smatch static
> checker warning:
> 
> 	drivers/powercap/arm_scmi_powercap.c:214 scmi_powercap_get_max_power_uw()
> 	warn: cast after binop
> 
> drivers/powercap/arm_scmi_powercap.c
>    203  static int scmi_powercap_get_max_power_uw(struct powercap_zone *pz, int cid,
>    204                                            u64 *max_power_uw)
>    205  {
>    206          struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
>    207  
>    208          if (!spz->info)
>    209                  return -ENODEV;
>    210  
>    211          if (spz->info->powercap_scale_uw)
>    212                  *max_power_uw = (u64)spz->info->max_power_cap;
>    213          else
>    214                  *max_power_uw = (u64)(spz->info->max_power_cap * 1000);
> 
> What's the deal with this cast?  It would make more sense to do the cast
> before the * 1000 so that it doesn't overflow the 32 bits.  Is the cast
> even required though?  The cast on the line before is decorative so
> maybe it's not required.
> 

Yes indeed, I suspect it's a leftover from a previous implementation I
did. There are also other unneeded u64 casts indeed.

In fact this driver was NOT pulled with the last SCMI v3.1 updates/fixes given
the very scarce review it got upstream (as you can see...)

I'll review all of these and integrate your other fixes in my next post
of the SCMI Arm poercap driver.

Thanks,
Cristian