Messages in this thread | | | Subject | Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver | From | John Garry <> | Date | Tue, 28 Jan 2020 14:46:07 +0000 |
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On 28/01/2020 12:50, Arnd Bergmann wrote:
Hi Arnd,
> On Tue, Jan 28, 2020 at 12:18 PM John Garry <john.garry@huawei.com> wrote: >> >> Add a generic driver for platforms which populate their ACPI PPTT >> processor package ID Type Structure according to suggestion in the ACPI >> spec - see ACPI 6.2, section 5.2.29.3 ID structure Type 2. >> >> The soc_id is from member LEVEL_2_ID. >> >> For this, we need to use a whitelist of platforms which are known to >> populate the structure as suggested. >> >> For now, only the vendor and soc_id fields are exposed. >> >> Signed-off-by: John Garry <john.garry@huawei.com> > > Would it be possible to make this the root device for all on-chip devices > to correctly reflect the hierarchy inside of the soc?
I don't think so. The information about the SoC is got from the PPTT, which only describes processors, caches, and physical package boundaries. It doesn't include references to on-chip devices.
Having said that (and unrelated to this series), we could add /sys/devices/system/soc folder, similar to node folder.
> >> +/* >> + * Known platforms that fill in PPTT package ID structures according to >> + * ACPI spec examples, that being: >> + * - Custom driver attribute is in ID Type Structure VENDOR_ID member >> + * - SoC id is in ID Type Structure LEVEL_2_ID member >> + * See ACPI SPEC 6.2 Table 5-154 for PPTT ID Type Structure >> + */ >> +static struct acpi_platform_list plat_list[] = { >> + {"HISI ", "HIP08 ", 0, ACPI_SIG_PPTT, all_versions}, >> + { } /* End */ >> +}; > > That matches a single machine, right? It doesn't seem very generic > that way.
Yes :) The problem is that the PPTT ID structure is open to use how the implementer wants, so we can't assume everything/anything implemented according to the spec examples. Maybe we could call it type1 or something like that for platforms which did use the convention in the spec example.
> >> +struct acpi_generic_soc_struct { >> + struct soc_device_attribute dev_attr; >> + u32 vendor; >> +}; >> + >> +static ssize_t vendor_show(struct device *dev, >> + struct device_attribute *attr, >> + char *buf) >> +{ >> + struct acpi_generic_soc_struct *soc = dev_get_drvdata(dev); >> + u8 vendor_id[5] = {}; >> + >> + *(u32 *)vendor_id = soc->vendor; >> + >> + return sprintf(buf, "%s\n", vendor_id); >> +} > > I'd rather not see nonstandard attributes in a "generic" driver at > all. Maybe the > you can simply concatenate the vendor and LEVEL_2_ID into a single string > here?
I actually don't really require the vendor attr. And since "vendor" is not in the set of standard soc driver attrs, it can just be omitted.
> >> + soc = kzalloc(sizeof(*soc), GFP_KERNEL); >> + if (!soc) >> + return -ENOMEM; >> + >> + soc_dev_attr = &soc->dev_attr; >> + soc_dev_attr->soc_id = kasprintf(GFP_KERNEL, "%s", >> + soc_id); > > On the other hand, it would make sense to fill out additional fields here. > You have already matched the name of the board from the > acpi_platform_list, so there are two strings available that could be put > into the "machine" field, and it would make sense to fill out "family" with > something that identifies it as coming from ACPI PPTT data.
OK, maybe the ones you suggested could be added. I did just want to start out with a minimal sets of files, especially since we don't always have a direct mapping between soc driver attrs and this PPTT ID structure.
Thanks, John
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