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

[Jeremy Linton]

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@xxxxxxx> 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@xxxxxxx>
> > Acked-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> > ---
> >   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.