linux-kernel - Re: [PATCH] powernv: powercap: Add hard minimum powercap

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Message-ID: <871s3s34jb.fsf@dja-thinkpad.axtens.net>
Date:   Thu, 28 Feb 2019 15:44:56 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        mpe@...erman.id.au
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ego@...ux.vnet.ibm.com,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powernv: powercap: Add hard minimum powercap

Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com> writes:

> In POWER9, OCC(On-Chip-Controller) provides for hard and soft system
> powercapping range. The hard powercap range is guaranteed while soft
> powercap may or may not be asserted due to various power-thermal
> reasons based on system configuration and workloads. This patch adds
> a sysfs file to export the hard minimum powercap limit to allow the
> user to set the appropriate powercap value that can be managed by the
> system.

Maybe it's common terminology and I'm just not aware of it, but what do
you mean by "asserted"? It doesn't appear elsewhere in the documentation
you're patching, and it's not a use of assert that I'm familiar with...

Regards,
Daniel

>
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
> ---
>  .../ABI/testing/sysfs-firmware-opal-powercap       | 10 ++++
>  arch/powerpc/platforms/powernv/opal-powercap.c     | 66 +++++++++-------------
>  2 files changed, 37 insertions(+), 39 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-firmware-opal-powercap b/Documentation/ABI/testing/sysfs-firmware-opal-powercap
> index c9b66ec..65db4c1 100644
> --- a/Documentation/ABI/testing/sysfs-firmware-opal-powercap
> +++ b/Documentation/ABI/testing/sysfs-firmware-opal-powercap
> @@ -29,3 +29,13 @@ Description:	System powercap directory and attributes applicable for
>  		  creates a request for setting a new-powercap. The
>  		  powercap requested must be between powercap-min
>  		  and powercap-max.
> +
> +What:		/sys/firmware/opal/powercap/system-powercap/powercap-hard-min
> +Date:		Feb 2019
> +Contact:	Linux for PowerPC mailing list <linuxppc-dev@...abs.org>
> +Description:	Hard minimum powercap
> +
> +		This file provides the hard minimum powercap limit in
> +		Watts. The powercap value above hard minimum is always
> +		guaranteed to be asserted and the powercap value below
> +		the hard minimum limit may or may not be guaranteed.
> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
> index d90ee4f..38408e7 100644
> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
> @@ -139,10 +139,24 @@ static void powercap_add_attr(int handle, const char *name,
>  	attr->handle = handle;
>  	sysfs_attr_init(&attr->attr.attr);
>  	attr->attr.attr.name = name;
> -	attr->attr.attr.mode = 0444;
> +
> +	if (!strncmp(name, "powercap-current", strlen(name))) {
> +		attr->attr.attr.mode = 0664;
> +		attr->attr.store = powercap_store;
> +	} else {
> +		attr->attr.attr.mode = 0444;
> +	}
> +
>  	attr->attr.show = powercap_show;
>  }
>  
> +static const char * const powercap_strs[] = {
> +	"powercap-max",
> +	"powercap-min",
> +	"powercap-current",
> +	"powercap-hard-min",
> +};
> +
>  void __init opal_powercap_init(void)
>  {
>  	struct device_node *powercap, *node;
> @@ -167,60 +181,34 @@ void __init opal_powercap_init(void)
>  
>  	i = 0;
>  	for_each_child_of_node(powercap, node) {
> -		u32 cur, min, max;
> -		int j = 0;
> -		bool has_cur = false, has_min = false, has_max = false;
> +		u32 id;
> +		int j, count = 0;
>  
> -		if (!of_property_read_u32(node, "powercap-min", &min)) {
> -			j++;
> -			has_min = true;
> -		}
> -
> -		if (!of_property_read_u32(node, "powercap-max", &max)) {
> -			j++;
> -			has_max = true;
> -		}
> +		for (j = 0; j < ARRAY_SIZE(powercap_strs); j++)
> +			if (!of_property_read_u32(node, powercap_strs[j], &id))
> +				count++;
>  
> -		if (!of_property_read_u32(node, "powercap-current", &cur)) {
> -			j++;
> -			has_cur = true;
> -		}
> -
> -		pcaps[i].pattrs = kcalloc(j, sizeof(struct powercap_attr),
> +		pcaps[i].pattrs = kcalloc(count, sizeof(struct powercap_attr),
>  					  GFP_KERNEL);
>  		if (!pcaps[i].pattrs)
>  			goto out_pcaps_pattrs;
>  
> -		pcaps[i].pg.attrs = kcalloc(j + 1, sizeof(struct attribute *),
> +		pcaps[i].pg.attrs = kcalloc(count + 1,
> +					    sizeof(struct attribute *),
>  					    GFP_KERNEL);
>  		if (!pcaps[i].pg.attrs) {
>  			kfree(pcaps[i].pattrs);
>  			goto out_pcaps_pattrs;
>  		}
>  
> -		j = 0;
>  		pcaps[i].pg.name = kasprintf(GFP_KERNEL, "%pOFn", node);
> -		if (has_min) {
> -			powercap_add_attr(min, "powercap-min",
> -					  &pcaps[i].pattrs[j]);
> -			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
> -			j++;
> -		}
> -
> -		if (has_max) {
> -			powercap_add_attr(max, "powercap-max",
> -					  &pcaps[i].pattrs[j]);
> -			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
> -			j++;
> -		}
> +		for (j = 0; j < ARRAY_SIZE(powercap_strs); j++) {
> +			if (of_property_read_u32(node, powercap_strs[j], &id))
> +				continue;
>  
> -		if (has_cur) {
> -			powercap_add_attr(cur, "powercap-current",
> +			powercap_add_attr(id, powercap_strs[j],
>  					  &pcaps[i].pattrs[j]);
> -			pcaps[i].pattrs[j].attr.attr.mode |= 0220;
> -			pcaps[i].pattrs[j].attr.store = powercap_store;
>  			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
> -			j++;
>  		}
>  
>  		if (sysfs_create_group(powercap_kobj, &pcaps[i].pg)) {
> -- 
> 1.8.3.1