Re: [PATCH v2 1/8] reset: modify the way reset lookup works for board files

[Bartosz Golaszewski]

2018-03-23 11:24 GMT+01:00 Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>:
> Hi Bartosz,
>
> On Fri, 2018-03-23 at 10:36 +0100, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
>>
>> Commit 7af1bb19f1d7 ("reset: add support for non-DT systems")
>> introduced reset control lookup mechanism for boards that still use
>> board files.
>>
>> The routine used to register lookup entries takes the corresponding
>> reset_controlled_dev structure as argument.
>>
>> It's been determined however that for the first user of this new
>> interface - davinci psc driver - it will be easier to register the
>> lookup entries using the reset controller device name.
>
> Thank you, this is what I expected in the first place.
>
>> This patch changes the way lookup entries are added.
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
>> ---
>>  drivers/reset/core.c             | 33 +++++++++++++++++++++++++++++----
>>  include/linux/reset-controller.h |  8 +++++---
>>  2 files changed, 34 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
>> index 06fa4907afc4..f37048e55336 100644
>> --- a/drivers/reset/core.c
>> +++ b/drivers/reset/core.c
>> @@ -153,11 +153,11 @@ EXPORT_SYMBOL_GPL(devm_reset_controller_register);
>>
>>  /**
>>   * reset_controller_add_lookup - register a set of lookup entries
>> - * @rcdev: initialized reset controller device owning the reset line
>> + * @provider: name of the reset controller provider
>>   * @lookup: array of reset lookup entries
>>   * @num_entries: number of entries in the lookup array
>>   */
>> -void reset_controller_add_lookup(struct reset_controller_dev *rcdev,
>> +void reset_controller_add_lookup(const char *provider,
>
> Is there any reason not to drop the provider parameter completely?
> I'd just let the user add the provider device id to the lookup, see
> below.
>
>>                                struct reset_control_lookup *lookup,
>>                                unsigned int num_entries)
>>  {
>> @@ -174,7 +174,7 @@ void reset_controller_add_lookup(struct reset_controller_dev *rcdev,
>>                       continue;
>>               }
>>
>> -             entry->rcdev = rcdev;
>> +             entry->provider = provider;
>>               list_add_tail(&entry->list, &reset_lookup_list);
>>       }
>>       mutex_unlock(&reset_lookup_mutex);
>> @@ -526,11 +526,30 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
>>  }
>>  EXPORT_SYMBOL_GPL(__of_reset_control_get);
>>
>> +static struct reset_controller_dev *
>> +__reset_controller_by_name(const char *name)
>> +{
>> +     struct reset_controller_dev *rcdev;
>> +
>> +     lockdep_assert_held(&reset_list_mutex);
>> +
>> +     list_for_each_entry(rcdev, &reset_controller_list, list) {
>> +             if (!rcdev->dev)
>> +                     continue;
>> +
>> +             if (!strcmp(name, dev_name(rcdev->dev)))
>> +                     return rcdev;
>> +     }
>> +
>> +     return NULL;
>> +}
>> +
>>  static struct reset_control *
>>  __reset_control_get_from_lookup(struct device *dev, const char *con_id,
>>                               bool shared, bool optional)
>>  {
>>       const struct reset_control_lookup *lookup;
>> +     struct reset_controller_dev *rcdev;
>>       const char *dev_id = dev_name(dev);
>>       struct reset_control *rstc = NULL;
>>
>> @@ -547,7 +566,13 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
>>                   ((con_id && lookup->con_id) &&
>>                    !strcmp(con_id, lookup->con_id))) {
>>                       mutex_lock(&reset_list_mutex);
>> -                     rstc = __reset_control_get_internal(lookup->rcdev,
>> +                     rcdev = __reset_controller_by_name(lookup->provider);
>> +                     if (!rcdev) {
>> +                             mutex_unlock(&reset_list_mutex);
>> +                             continue;
>
> What is the reason to continue here? If we've found a matching lookup
> that contains a rcdev dev_id for which there is no reset controller,
> shouldn't we just return an error?
>

Indeed. This could be used to indicate to drivers that the reset
controller may not have yet been probed() or its probe() failed. How
about returning -EPROBE_DEFER here?

Bart

>> +                     }
>> +
>> +                     rstc = __reset_control_get_internal(rcdev,
>>                                                           lookup->index,
>>                                                           shared);
>>                       mutex_unlock(&reset_list_mutex);
>> diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h
>> index 25698f6c1fae..1a6c25d825d3 100644
>> --- a/include/linux/reset-controller.h
>> +++ b/include/linux/reset-controller.h
>> @@ -30,14 +30,14 @@ struct of_phandle_args;
>>   * struct reset_control_lookup - represents a single lookup entry
>>   *
>>   * @list: internal list of all reset lookup entries
>> - * @rcdev: reset controller device controlling this reset line
>> + * @provider: name of the reset controller device controlling this reset line
>>   * @index: ID of the reset controller in the reset controller device
>>   * @dev_id: name of the device associated with this reset line
>>   * @con_id name of the reset line (can be NULL)
>>   */
>>  struct reset_control_lookup {
>>       struct list_head list;
>> -     struct reset_controller_dev *rcdev;
>> +     const char *provider;
>
> Looks good to me, but I'd also extend RESET_LOOKUP to set the provider
> instead of passing it to the reset_controller_add_lookup function,
> similarly to PWM_LOOKUP:
>
> #define RESET_LOOKUP(_provider, _index, _dev_id, _con_id)
>

I did it mostly for brevity - I don't mind changing it if you prefer
this version.

Thanks,
Bart