[Skiboot] [PATCH v3] powercap: occ: Fix the powercapping range allowed for user

[Vaidyanathan Srinivasan]

* Shilpa Bhat <shilpa.bhat at linux.vnet.ibm.com> [2019-02-05 10:44:52]:

> OCC provides two limits for minimum powercap. One being hard powercap
> minimum which is guaranteed by OCC and the other one is a soft
> powercap minimum which is lesser than hard-min and may or may not be
> asserted due to various power-thermal reasons. So to allow the users
> to access the entire powercap range, this patch exports soft powercap
> minimum as the "powercap-min" DT property. And it also adds a new
> DT property called "powercap-hard-min" to export the hard-min powercap
> limit.
> 
> Fixes: c6aabe3f2eb5("powercap: occ: Add a generic powercap framework")
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com>

Reviewed-by:  Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>


> ---
> Changes from V2:
> - As per Vaidy's suggestion change powercap-min to point to
>   soft-powercap min limit instead of hard-powercap as min and max
>   should point to the absolute possible range.
> 
>  doc/device-tree/ibm,opal/power-mgt/powercap.rst |  9 +++++++-
>  hw/occ.c                                        | 30 ++++++++++++++++++-------
>  2 files changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/doc/device-tree/ibm,opal/power-mgt/powercap.rst b/doc/device-tree/ibm,opal/power-mgt/powercap.rst
> index 5a8d007..5d24ee1 100644
> --- a/doc/device-tree/ibm,opal/power-mgt/powercap.rst
> +++ b/doc/device-tree/ibm,opal/power-mgt/powercap.rst
> @@ -20,11 +20,17 @@ Each child node has below properties:
>    Handle to indicate the current powercap
> 
>  `powercap-min`
> -  Minimum possible powercap
> +  Absolute minimum possible powercap. This points to the soft powercap minimum
> +  limit as exported by OCC. The powercap set in the soft powercap range may or
> +  may not be maintained.
> 
>  `powercap-max`
>    Maximum possible powercap
> 
> +`powercap-hard-min`
> +  This value points to the hard minimum powercap limit. The powercap set above
> +  this limit is guaranteed unless there is a hardware failure
> +
>  Powercap handle uses the following encoding: ::
> 
>          | Class |    Reserved   | Attribute |
> @@ -44,6 +50,7 @@ the future.
>                  powercap-current = <0x00000002>;
>                  powercap-min = <0x00000000>;
>                  powercap-max = <0x00000001>;
> +                powercap-hard-min = <0x000000003>;
>          };
>       };
>      };
> diff --git a/hw/occ.c b/hw/occ.c
> index 9580bb8..e290937 100644
> --- a/hw/occ.c
> +++ b/hw/occ.c
> @@ -225,9 +225,12 @@ struct occ_response_buffer {
>   *				power to maintain a power cap. Value of 100
>   *				means take all power from CPU.
>   * @pwr_cap_type:		Indicates type of power cap in effect
> - * @min_pwr_cap:		Minimum allowed system power cap in Watts
> + * @hard_min_pwr_cap:		Hard minimum system power cap in Watts.
> + *				Guaranteed unless hardware failure
>   * @max_pwr_cap:		Maximum allowed system power cap in Watts
>   * @cur_pwr_cap:		Current system power cap
> + * @soft_min_pwr_cap:		Soft powercap minimum. OCC may or may not be
> + *				able to maintain this
>   * @spare/reserved:		Unused data
>   * @cmd:			Opal Command Buffer
>   * @rsp:			OCC Response Buffer
> @@ -243,10 +246,11 @@ struct occ_dynamic_data {
>  	u8 quick_pwr_drop;
>  	u8 pwr_shifting_ratio;
>  	u8 pwr_cap_type;
> -	u16 min_pwr_cap;
> +	u16 hard_min_pwr_cap;
>  	u16 max_pwr_cap;
>  	u16 cur_pwr_cap;
> -	u8 pad[112];
> +	u16 soft_min_pwr_cap;
> +	u8 pad[110];
>  	struct opal_command_buffer cmd;
>  	struct occ_response_buffer rsp;
>  } __packed;
> @@ -1324,9 +1328,10 @@ static void occ_cmd_interface_init(void)
> 
>  /* Powercap interface */
>  enum sensor_powercap_occ_attr {
> -	POWERCAP_OCC_MIN,
> +	POWERCAP_OCC_SOFT_MIN,
>  	POWERCAP_OCC_MAX,
>  	POWERCAP_OCC_CUR,
> +	POWERCAP_OCC_HARD_MIN,
>  };
> 
>  static void occ_add_powercap_sensors(struct dt_node *power_mgt)
> @@ -1350,11 +1355,17 @@ static void occ_add_powercap_sensors(struct dt_node *power_mgt)
>  	handle = powercap_make_handle(POWERCAP_CLASS_OCC, POWERCAP_OCC_CUR);
>  	dt_add_property_cells(node, "powercap-current", handle);
> 
> -	handle = powercap_make_handle(POWERCAP_CLASS_OCC, POWERCAP_OCC_MIN);
> +	handle = powercap_make_handle(POWERCAP_CLASS_OCC,
> +				      POWERCAP_OCC_SOFT_MIN);
>  	dt_add_property_cells(node, "powercap-min", handle);
> 
>  	handle = powercap_make_handle(POWERCAP_CLASS_OCC, POWERCAP_OCC_MAX);
>  	dt_add_property_cells(node, "powercap-max", handle);
> +
> +	handle = powercap_make_handle(POWERCAP_CLASS_OCC,
> +				      POWERCAP_OCC_HARD_MIN);
> +	dt_add_property_cells(node, "powercap-hard-min", handle);
> +
>  }
> 
>  int occ_get_powercap(u32 handle, u32 *pcap)
> @@ -1371,8 +1382,8 @@ int occ_get_powercap(u32 handle, u32 *pcap)
>  		return OPAL_HARDWARE;
> 
>  	switch (powercap_get_attr(handle)) {
> -	case POWERCAP_OCC_MIN:
> -		*pcap = ddata->min_pwr_cap;
> +	case POWERCAP_OCC_SOFT_MIN:
> +		*pcap = ddata->soft_min_pwr_cap;
>  		break;
>  	case POWERCAP_OCC_MAX:
>  		*pcap = ddata->max_pwr_cap;
> @@ -1380,6 +1391,9 @@ int occ_get_powercap(u32 handle, u32 *pcap)
>  	case POWERCAP_OCC_CUR:
>  		*pcap = ddata->cur_pwr_cap;
>  		break;
> +	case POWERCAP_OCC_HARD_MIN:
> +		*pcap = ddata->hard_min_pwr_cap;
> +		break;
>  	default:
>  		*pcap = 0;
>  		return OPAL_UNSUPPORTED;
> @@ -1420,7 +1434,7 @@ int occ_set_powercap(u32 handle, int token, u32 pcap)
>  		return OPAL_SUCCESS;
> 
>  	if (pcap && (pcap > ddata->max_pwr_cap ||
> -	    pcap < ddata->min_pwr_cap))
> +	    pcap < ddata->soft_min_pwr_cap))
>  		return OPAL_PARAMETER;
> 
>  	pcap_cdata = pcap;

This change will allow end users to set power cap for full range.  The
lower the power cap value, the system may exceed it more often because
it will be in the soft-power cap range.  

Based on system configuration and workloads, users are expected to set
appropriate value for power cap that can be managed by the system.

--Vaidy