Re: [PATCH 5/7] ACPI: scan: Add support for deferring adding devices to the second scan phase based on the _DEP list

Hans de Goede
2020-11-23T13:31:11Z

Hi,

On 11/23/20 1:17 PM, Rafael J. Wysocki wrote:
> On Sat, Nov 21, 2020 at 9:31 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> The current solution, of deferring adding of some devices because they
>> need access during the OpRegions of other devices while they are added,
>> is not very generic.
>>
>> And support for making the decision to defer adding a device based on
>> its _DEP list, instead of the device's HID being in a fixed list of HIDs
>> to defer, which should be a more generic way to deal with this.
>
> Thanks a lot for working on this!

You're welcome.

> I'll have a more thorough look at the series later this week, stay tuned.

Ok.

>> Since this is likely to cause issues on some hardware, this new method will
>> only be used if the new acpi.defer_scan_based_on_dep kernel commandline
>> option is set to 1.
>
> However, I already can say that I don't like the new command line option.

You don't like the name, or you don't like having a commandline option for this?

Anyways I'll wait till you have taken a closer look.

Regards,

Hans

>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> drivers/acpi/scan.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 44 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 407c8536568b..9927036bfe77 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -31,6 +31,11 @@ extern struct acpi_device *acpi_root;
>>
>> #define INVALID_ACPI_HANDLE ((acpi_handle)empty_zero_page)
>>
>> +static int defer_scan_based_on_dep = -1;
>> +module_param(defer_scan_based_on_dep, int, 0444);
>> +MODULE_PARM_DESC(defer_scan_based_on_dep,
>> + "Use new scan-scheme deferring addition of devices with non empty _DEP list (-1=auto, 0=no, 1=yes)");
>> +
>> static const char *dummy_hid = "device";
>>
>> static LIST_HEAD(acpi_dep_list);
>> @@ -1657,11 +1662,45 @@ void acpi_device_add_finalize(struct acpi_device *device)
>>
>> static bool acpi_should_defer_add(acpi_handle handle, struct acpi_device_info *info)
>> {
>> + struct acpi_handle_list dep_devices;
>> + acpi_status status;
>> + int i;
>> +
>> if (!acpi_check_defer_add || !info)
>> return false;
>>
>> - if (acpi_info_matches_hids(info, acpi_defer_add_hids))
>> + if (!defer_scan_based_on_dep)
>> + return acpi_info_matches_hids(info, acpi_defer_add_hids);
>> +
>> + /*
>> + * We check for _ADR here to avoid deferring the adding of the following:
>> + * 1. PCI devices
>> + * 2. ACPI nodes describing USB ports
>> + * Note checking for _ADR catches more then just these cases...
>
> s/then/than/
>
>> + */
>> + if (info->valid & ACPI_VALID_ADR)
>> + return false;
>> +
>> + status = acpi_evaluate_reference(handle, "_DEP", NULL, &dep_devices);
>> + if (ACPI_FAILURE(status))
>> + return false;
>> +
>> + for (i = 0; i < dep_devices.count; i++) {
>> + struct acpi_device_info *dep_info;
>> + bool ignore;
>> +
>> + status = acpi_get_object_info(dep_devices.handles[i], &dep_info);
>> + if (ACPI_FAILURE(status))
>> + continue;
>> +
>> + ignore = acpi_info_matches_hids(dep_info, acpi_ignore_dep_hids);
>> + kfree(dep_info);
>> +
>> + if (ignore)
>> + continue;
>> +
>> return true;
>> + }
>>
>> return false;
>> }
>> @@ -2251,6 +2290,10 @@ int __init acpi_scan_init(void)
>> struct acpi_table_stao *stao_ptr;
>> struct acpi_deferred_dev *deferred_dev, *tmp;
>>
>> + /* Currently no devices are known which need _dep based scan deferral */
>> + if (defer_scan_based_on_dep == -1)
>> + defer_scan_based_on_dep = 0;
>> +
>> acpi_pci_root_init();
>> acpi_pci_link_init();
>> acpi_processor_init();
>> --
>> 2.28.0
>>
>