Re: [PATCH 3/9] powerpc/pseries: Add cpu DLPAR support for drc-info property

[Thomas Falcon <tlfalcon@linux.ibm.com>]

On 11/5/19 9:24 AM, Tyrel Datwyler wrote:
> From: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
>
> Older firmwares provided information about Dynamic Reconfig
> Connectors (DRC) through several device tree properties, namely
> ibm,drc-types, ibm,drc-indexes, ibm,drc-names, and
> ibm,drc-power-domains. New firmwares have the ability to present this
> same information in a much condensed format through a device tree
> property called ibm,drc-info.
>
> The existing cpu DLPAR hotplug code only understands the older DRC
> property format when validating the drc-index of a cpu during a
> hotplug add. This updates those code paths to use the ibm,drc-info
> property, when present, instead for validation.
>
> Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
> ---
>   arch/powerpc/platforms/pseries/hotplug-cpu.c | 101 ++++++++++++++++++++++-----
>   1 file changed, 85 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> index bbda646..9ba006c 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> @@ -407,17 +407,58 @@ static bool dlpar_cpu_exists(struct device_node *parent, u32 drc_index)
>   	return found;
>   }
>
> +static bool drc_info_valid_index(struct device_node *parent, u32 drc_index)
> +{
> +	struct property *info;
> +	struct of_drc_info drc;
> +	const __be32 *value;
> +	int count, i, j;
> +
> +	info = of_find_property(parent, "ibm,drc-info", NULL);
> +	if (!info)
> +		return false;
> +
> +	value = of_prop_next_u32(info, NULL, &count);
> +
> +	/* First value of ibm,drc-info is number of drc-info records */
> +	if (value)
> +		value++;
> +	else
> +		return false;
> +
> +	for (i = 0; i < count; i++) {
> +		if (of_read_drc_info_cell(&info, &value, &drc))
> +			return false;
> +
> +		if (strncmp(drc.drc_type, "CPU", 3))
> +			break;
> +
> +		if (drc_index > drc.last_drc_index)
> +			continue;
> +
> +		for (j = 0; j < drc.num_sequential_elems; j++)
> +			if (drc_index == (drc.drc_index_start + (drc.sequential_inc * j)))
> +					return true;
> +	}
> +
> +	return false;
> +}
> +
>   static bool valid_cpu_drc_index(struct device_node *parent, u32 drc_index)
>   {
>   	bool found = false;
>   	int rc, index;
>
> -	index = 0;
> +	if (of_find_property(parent, "ibm,drc-info", NULL))
> +		return drc_info_valid_index(parent, drc_index);
> +
> +	index = 1;

Hi, this change was confusing to me until I continued reading the patch 
and saw the comment below regarding the first element of the 
ibm,drc-info property.  Would it be good to have a similar comment here too?


>   	while (!found) {
>   		u32 drc;
>
>   		rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
>   						index++, &drc);
> +

Another nitpick but this could be cleaned up.

Thanks,

Tom


>   		if (rc)
>   			break;
>
> @@ -720,8 +761,11 @@ static int dlpar_cpu_remove_by_count(u32 cpus_to_remove)
>   static int find_dlpar_cpus_to_add(u32 *cpu_drcs, u32 cpus_to_add)
>   {
>   	struct device_node *parent;
> +	struct property *info;
>   	int cpus_found = 0;
>   	int index, rc;
> +	int i, j;
> +	u32 drc_index;
>
>   	parent = of_find_node_by_path("/cpus");
>   	if (!parent) {
> @@ -730,24 +774,49 @@ static int find_dlpar_cpus_to_add(u32 *cpu_drcs, u32 cpus_to_add)
>   		return -1;
>   	}
>
> -	/* Search the ibm,drc-indexes array for possible CPU drcs to
> -	 * add. Note that the format of the ibm,drc-indexes array is
> -	 * the number of entries in the array followed by the array
> -	 * of drc values so we start looking at index = 1.
> -	 */
> -	index = 1;
> -	while (cpus_found < cpus_to_add) {
> -		u32 drc;
> +	info = of_find_property(parent, "ibm,drc-info", NULL);
> +	if (info) {
> +		struct of_drc_info drc;
> +		const __be32 *value;
> +		int count;
>
> -		rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
> -						index++, &drc);
> -		if (rc)
> -			break;
> +		value = of_prop_next_u32(info, NULL, &count);
> +		if (value)
> +			value++;
>
> -		if (dlpar_cpu_exists(parent, drc))
> -			continue;
> +		for (i = 0; i < count; i++) {
> +			of_read_drc_info_cell(&info, &value, &drc);
> +			if (strncmp(drc.drc_type, "CPU", 3))
> +				break;
> +
> +			for (j = 0; j < drc.num_sequential_elems && cpus_found < cpus_to_add; j++) {
> +				drc_index = drc.drc_index_start + (drc.sequential_inc * j);
> +
> +				if (dlpar_cpu_exists(parent, drc_index))
> +					continue;
> +
> +				cpu_drcs[cpus_found++] = drc_index;
> +			}
> +		}
> +	} else {
> +		/* Search the ibm,drc-indexes array for possible CPU drcs to
> +		 * add. Note that the format of the ibm,drc-indexes array is
> +		 * the number of entries in the array followed by the array
> +		 * of drc values so we start looking at index = 1.
> +		 */
> +		index = 1;
> +		while (cpus_found < cpus_to_add) {
> +			rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
> +							index++, &drc_index);
> +
> +			if (rc)
> +				break;
>
> -		cpu_drcs[cpus_found++] = drc;
> +			if (dlpar_cpu_exists(parent, drc_index))
> +				continue;
> +
> +			cpu_drcs[cpus_found++] = drc_index;
> +		}
>   	}
>
>   	of_node_put(parent);