Re: [PATCH v8 05/13] ACPI/PPTT: Add Processor Properties Topology Table parsing

[Jeremy Linton <jeremy.linton@arm.com>]

Hi,

Thanks for taking a look at this.

On 04/27/2018 06:02 AM, Rafael J. Wysocki wrote:
> On Thu, Apr 26, 2018 at 1:31 AM, Jeremy Linton <jeremy.linton@arm.com> wrote:
>> ACPI 6.2 adds a new table, which describes how processing units
>> are related to each other in tree like fashion. Caches are
>> also sprinkled throughout the tree and describe the properties
>> of the caches in relation to other caches and processing units.
>>
>> Add the code to parse the cache hierarchy and report the total
>> number of levels of cache for a given core using
>> acpi_find_last_cache_level() as well as fill out the individual
>> cores cache information with cache_setup_acpi() once the
>> cpu_cacheinfo structure has been populated by the arch specific
>> code.
>>
>> An additional patch later in the set adds the ability to report
>> peers in the topology using find_acpi_cpu_topology()
>> to report a unique ID for each processing unit at a given level
>> in the tree. These unique id's can then be used to match related
>> processing units which exist as threads, within a given
>> package, etc.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
>> Acked-by: Sudeep Holla <sudeep.holla@arm.com>
>> ---
>>   drivers/acpi/pptt.c | 518 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 518 insertions(+)
>>   create mode 100644 drivers/acpi/pptt.c
>>
>> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
>> new file mode 100644
>> index 000000000000..cced71ef851a
>> --- /dev/null
>> +++ b/drivers/acpi/pptt.c
>> @@ -0,0 +1,518 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * pptt.c - parsing of Processor Properties Topology Table
>> + *
>> + * Copyright (C) 2018, ARM
>> + *
>> + * This file implements parsing of Processor Properties Topology Table (PPTT)
>> + * which is optionally used to describe the processor and cache topology.
>> + * Due to the relative pointers used throughout the table, this doesn't
>> + * leverage the existing subtable parsing in the kernel.
>> + *
>> + * The PPTT structure is an inverted tree, with each node potentially
>> + * holding one or two inverted tree data structures describing
>> + * the caches available at that level. Each cache structure optionally
>> + * contains properties describing the cache at a given level which can be
>> + * used to override hardware probed values.
>> + */
>> +#define pr_fmt(fmt) "ACPI PPTT: " fmt
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/cacheinfo.h>
>> +#include <acpi/processor.h>
>> +
>> +/**
>> + * fetch_pptt_subtable() - Find/Verify that the PPTT ref is a valid subtable
> 
> The parens above are at least redundant (if not harmful).  Everywhere
> else in a similar context too.

The kerneldoc ones? I guess i'm confused the kernel doc example in 
doc-guide/kernel-doc has

* function_name() - Brief description of function.


> 
> Also kerneldoc comments document function arguments too as a rule, so
> please do that here and wherever you use kerneldoc comments in the
> patchset.

Ok, sure.

> 
>> + *
>> + * Given the PPTT table, find and verify that the subtable entry
>> + * is located within the table
>> + *
>> + * Return: acpi_subtable_header* or NULL
>> + */
>> +static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
>> +                                                       u32 pptt_ref)
>> +{
>> +       struct acpi_subtable_header *entry;
>> +
>> +       /* there isn't a subtable at reference 0 */
>> +       if (pptt_ref < sizeof(struct acpi_subtable_header))
>> +               return NULL;
>> +
>> +       if (pptt_ref + sizeof(struct acpi_subtable_header) > table_hdr->length)
>> +               return NULL;
>> +
>> +       entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr, pptt_ref);
>> +
>> +       if (entry->length == 0)
>> +               return NULL;
>> +
>> +       if (pptt_ref + entry->length > table_hdr->length)
>> +               return NULL;
>> +
>> +       return entry;
>> +}
> 
> Apart from the above I'm not entirely sure why you need the changes in
> patch [09/13] to go in a separate patch.  All of them are new code
> going into the file created by this patch, so why not to put them
> here?


Ok, I was doing that because Lorenzo asked for it, but he hasn't said 
much so I will collapse it back together. That makes me happy, as 
splitting chunks between patches is a pain anyway.