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

[Tyrel Datwyler <tyreld@linux.ibm.com>]

On 11/5/19 8:55 AM, Thomas Falcon wrote:
> 
> 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?
> 

Yeah, clearly wouldn't hurt. Probably should split it out into a separate fix
prior to this patch.

> 
>>       while (!found) {
>>           u32 drc;
>>
>>           rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
>>                           index++, &drc);
>> +
> 
> Another nitpick but this could be cleaned up.

Yep, noticed the newline addition after I'd already sent it out.

-Tyrel

> 
> 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);