Re: [PATCH 04/18] staging: typec: tcpm: Add helpers for exporting current-limit through a psy

[Guenter Roeck <linux@roeck-us.net>]

On 08/06/2017 07:21 AM, Hans de Goede wrote:
> Hi,
> 
> On 06-08-17 16:13, Guenter Roeck wrote:
>> On 08/06/2017 05:35 AM, Hans de Goede wrote:
>>> Not all type-c port-controller can control the current-limit directly,
>>> in cases where the current limit can not be controlled directly it needs
>>> to be exported so that another driver (e.g. the charger driver) can pick
>>> the limit up and configure the system accordingly.
>>>
>>> The power-supply subsys already provides infrastructure for this,
>>> power-supply devices have the notion of being supplied by another
>>> power-supply and have properties through which we can export the
>>> current-limit.
>>>
>>> This commits adds 2 helper functions for use by port-controller drivers
>>> which want to export the current-limit info in this way:
>>>
>>> int tcpm_register_psy(struct device *dev, struct tcpc_dev *tcpc,
>>>               const char *name);
>>> int tcpm_set_current_limit_psy(struct tcpc_dev *tcpc, u32 max_ma, u32 mv);
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>> ---
>>>   drivers/staging/typec/tcpm-helpers.c | 66 ++++++++++++++++++++++++++++++++++++
>>>   drivers/staging/typec/tcpm.h         |  9 +++++
>>>   2 files changed, 75 insertions(+)
>>>
>>> diff --git a/drivers/staging/typec/tcpm-helpers.c b/drivers/staging/typec/tcpm-helpers.c
>>> index 0c87ec9936e1..8f7699576878 100644
>>> --- a/drivers/staging/typec/tcpm-helpers.c
>>> +++ b/drivers/staging/typec/tcpm-helpers.c
>>> @@ -20,6 +20,60 @@
>>>   #include "tcpm.h"
>>> +static int tcpm_psy_get_property(struct power_supply *psy,
>>> +                 enum power_supply_property psp,
>>> +                 union power_supply_propval *val)
>>> +{
>>> +    struct tcpc_dev *tcpc = power_supply_get_drvdata(psy);
>>> +
>>> +    switch (psp) {
>>> +    case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>>> +        val->intval = tcpc->supply_voltage * 1000; /* mV -> µV */
>>> +        break;
>>> +    case POWER_SUPPLY_PROP_CURRENT_MAX:
>>> +        val->intval = tcpc->current_limit * 1000; /* mA -> µA */
>>> +        break;
>>> +    default:
>>> +        return -ENODATA;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static enum power_supply_property tcpm_psy_properties[] = {
>>> +    POWER_SUPPLY_PROP_VOLTAGE_NOW,
>>> +    POWER_SUPPLY_PROP_CURRENT_MAX,
>>> +};
>>> +
>>> +int tcpm_register_psy(struct device *dev, struct tcpc_dev *tcpc,
>>> +              const char *name)
>>
>> This is misleading since it relies on devm functions, and there is no unregister function.
> 
> The reliance on devm functions is intentional, that makes cleanup on probe() failure for users
> of this a lot easier. I guess we could rename this tcpm_initialize_psy(), although it does
> actually register a psy, so maybe: devm_tcpm_register_psy() to explain why there is no
> unregister counter-part ?
> 

I don't question the use of devm functions. Yes, I think devm_tcpm_register_psy() would be better.

>> Overall I am not too happy with tying this all into tcpm. The functions are not really tcpm
>> related. Not that I have a better idea how to handle this right now, but conceptually it
>> doesn't seem correct.
> 
> Note that no changes are made to the tcpm core in this entire patch-set, with the exception
> of the first patch which adds the get_usb2_current_limit callback.
> 
Yes, but you are using tcpm data structures. Of this entire series, I think only the callback
(renamed to get_usb_current_limit) should really be in tcpm code. Maybe it makes sense to find
a way to provide helpers in a generic way, if it turns out that the same code is needed by multiple
drivers, but right now they are only used by fusb302 and might as well stay there.

Until other drivers need them, we don't really know if the helpers are useful for multiple drivers.
I would prefer to add such helpers if and when we have more than one driver using them.

Thanks,
Guenter

> This really only ties into the port-controller driver, and as such uses tcpc_dev to store some
> stuff. I could make this more clear by prefixing the helper function names with tcpc instead of
> tcpm if you think that is better ?
> 
> Regards,
> 
> Hans
> 
> 
>>
>>> +{
>>> +    struct power_supply_config psy_cfg = {};
>>> +    struct power_supply_desc *desc;
>>> +    int ret = 0;
>>> +
>>> +    desc = devm_kzalloc(dev, sizeof(*desc), GFP_KERNEL);
>>> +    if (!desc)
>>> +        return -ENOMEM;
>>> +
>>> +    desc->name        = name;
>>> +    desc->type        = POWER_SUPPLY_TYPE_USB;
>>> +    desc->properties    = tcpm_psy_properties;
>>> +    desc->num_properties    = ARRAY_SIZE(tcpm_psy_properties);
>>> +    desc->get_property    = tcpm_psy_get_property;
>>> +    psy_cfg.drv_data    = tcpc;
>>> +
>>> +    tcpc->psy = devm_power_supply_register(dev, desc, &psy_cfg);
>>> +    if (IS_ERR(tcpc->psy)) {
>>> +        ret = PTR_ERR(tcpc->psy);
>>> +        tcpc->psy = NULL;
>>> +        dev_err(dev, "Error registering power-supply: %d\n", ret);
>>> +    }
>>> +
>>> +    return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(tcpm_register_psy);
>>> +
>>>   /* Generic (helper) implementations for some tcpc_dev callbacks */
>>>   int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc)
>>>   {
>>> @@ -58,3 +112,15 @@ int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc)
>>>       return current_limit;
>>>   }
>>>   EXPORT_SYMBOL_GPL(tcpm_get_usb2_current_limit_extcon);
>>> +
>>> +int tcpm_set_current_limit_psy(struct tcpc_dev *tcpc, u32 max_ma, u32 mv)
>>> +{
>>> +    tcpc->supply_voltage = mv;
>>> +    tcpc->current_limit = max_ma;
>>> +
>>> +    if (tcpc->psy)
>>> +        power_supply_changed(tcpc->psy);
>>> +
>>> +    return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(tcpm_set_current_limit_psy);
>>> diff --git a/drivers/staging/typec/tcpm.h b/drivers/staging/typec/tcpm.h
>>> index 35e8c1e7dba0..1b1475b487b5 100644
>>> --- a/drivers/staging/typec/tcpm.h
>>> +++ b/drivers/staging/typec/tcpm.h
>>> @@ -17,6 +17,7 @@
>>>   #include <linux/bitops.h>
>>>   #include <linux/extcon.h>
>>> +#include <linux/power_supply.h>
>>>   #include <linux/usb/typec.h>
>>>   #include "pd.h"
>>> @@ -129,6 +130,10 @@ struct tcpc_dev {
>>>       struct tcpc_mux_dev *mux;
>>>       /* Used by tcpm_get_usb2_current_limit_extcon helpers */
>>>       struct extcon_dev *usb2_extcon;
>>> +    /* Used by tcpm_set_current_limit_psy helpers */
>>> +    struct power_supply *psy;
>>> +    u32 current_limit;
>>> +    u32 supply_voltage;
>>>   };
>>>   struct tcpm_port;
>>> @@ -154,7 +159,11 @@ void tcpm_pd_transmit_complete(struct tcpm_port *port,
>>>   void tcpm_pd_hard_reset(struct tcpm_port *port);
>>>   void tcpm_tcpc_reset(struct tcpm_port *port);
>>> +int tcpm_register_psy(struct device *dev, struct tcpc_dev *tcpc,
>>> +              const char *name);
>>> +
>>>   /* Generic (helper) implementations for some tcpc_dev callbacks */
>>>   int tcpm_get_usb2_current_limit_extcon(struct tcpc_dev *tcpc);
>>> +int tcpm_set_current_limit_psy(struct tcpc_dev *tcpc, u32 max_ma, u32 mv);
>>>   #endif /* __LINUX_USB_TCPM_H */
>>>
>>
>