On 2/13/19 4:17 PM, Fabrice Gasnier wrote: > On 2/13/19 1:53 PM, Thierry Reding wrote: >> On Wed, Feb 13, 2019 at 11:50:12AM +0100, Fabrice Gasnier wrote: >>> Add a device link between the PWM consumer and the PWM provider. This >>> enforces the PWM user to get suspended before the PWM provider. It >>> allows proper synchronization of suspend/resume sequences: the PWM user >>> is responsible for properly stopping PWM, before the provider gets >>> suspended: see [1]. Add the device link in: >>> - of_pwm_get() >>> - pwm_get() >>> - devm_ variants >>> as it requires a reference to the device for the PWM consumer. >>> >>> [1] https://lkml.org/lkml/2019/2/5/770 >>> >>> Suggested-by: Thierry Reding <thierry.reding@xxxxxxxxx> >>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx> >>> --- >>> Changes in v3: >>> - add struct device to of_get_pwm() arguments to handle device link from >>> there. >>> --- >>> drivers/pwm/core.c | 14 +++++++++++--- >>> include/linux/pwm.h | 6 ++++-- >>> 2 files changed, 15 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c >>> index 1581f6a..8cb5d4bc 100644 >>> --- a/drivers/pwm/core.c >>> +++ b/drivers/pwm/core.c >>> @@ -638,6 +638,7 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np) >>> >>> /** >>> * of_pwm_get() - request a PWM via the PWM framework >>> + * @dev: device for PWM consumer >>> * @np: device node to get the PWM from >>> * @con_id: consumer name >>> * >>> @@ -655,7 +656,8 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np) >>> * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded >>> * error code on failure. >>> */ >>> -struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id) >>> +struct pwm_device *of_pwm_get(struct device *dev, struct device_node *np, >>> + const char *con_id) >>> { >>> struct pwm_device *pwm = NULL; >>> struct of_phandle_args args; >>> @@ -689,6 +691,9 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id) >>> if (IS_ERR(pwm)) >>> goto put; >>> >>> + if (!device_link_add(dev, pwm->chip->dev, DL_FLAG_AUTOREMOVE_CONSUMER)) >>> + pr_debug("%s(): device link not added\n", __func__); >> >> I think it's better to turn this into dev_dbg(dev, ...) and maybe >> mention which supplier it failed to link to, something like: >> >> if (!device_link_add(...)) >> dev_dbg(dev, "failed to create device link to %s\n", >> pwm->chip->dev); > > Hi Thierry, > > Thanks for reviewing. > > I can update this: I used pr_debug() as there are pr_err() calls > elsewhere in this routine. > BTW, do you wish an additional patch to turn pr_err() into dev_err() in > of_pwm_get()? > >> >> Also, I wonder if this should perhaps be dev_err(). Under what >> circumstances does this fail? > > Well, here is a comment from "device_link_add()" routine: > " > /* > * If the supplier has not been fully registered yet or there is a > * reverse dependency between the consumer and the supplier already in > * the graph, return NULL. > */ > " > > => Here the PWM supplier is already registered. (It seems a probe defer > can be returned few lines above otherwise.) > > Other possibilities: kzalloc() failed, no consumer or supplier has been > provided (or invalid flags, but this is hardcoded here.). > > So, I see two case here: > 1 - The caller provided a 'dev' for PWM consumer... So, NULL link is an > error when consumer & supplier has been passed correctly. > => I can add a check on 'dev' for PWM consumer and report an error here: > return -EINVAL > > 2 - The caller can't provide a 'dev' for PWM consumer as you mention > bellow: "to allow code to get at the PWM if they didn't have..." > => We should probably add a dev_warn() here, with no error ? > Please see here after. > >> >>> + >>> /* >>> * If a consumer name was not given, try to look it up from the >>> * "pwm-names" property if it exists. Otherwise use the name of >>> @@ -771,7 +776,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) >>> >>> /* look up via DT first */ >>> if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node) >>> - return of_pwm_get(dev->of_node, con_id); >>> + return of_pwm_get(dev, dev->of_node, con_id); >>> >>> /* >>> * We look up the provider in the static table typically provided by >>> @@ -851,6 +856,9 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) >>> pwm->args.period = chosen->period; >>> pwm->args.polarity = chosen->polarity; >>> >>> + if (!device_link_add(dev, pwm->chip->dev, DL_FLAG_AUTOREMOVE_CONSUMER)) >>> + pr_debug("%s(): device link not added\n", __func__); >> >> Same here. Also: not sure if we really need to include __func__ in the >> message. >> >>> + >>> return pwm; >>> } >>> EXPORT_SYMBOL_GPL(pwm_get); >>> @@ -939,7 +947,7 @@ struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np, >>> if (!ptr) >>> return ERR_PTR(-ENOMEM); >>> >>> - pwm = of_pwm_get(np, con_id); >>> + pwm = of_pwm_get(dev, np, con_id); >>> if (!IS_ERR(pwm)) { >>> *ptr = pwm; >>> devres_add(dev, ptr); >>> diff --git a/include/linux/pwm.h b/include/linux/pwm.h >>> index d5199b5..895e074 100644 >>> --- a/include/linux/pwm.h >>> +++ b/include/linux/pwm.h >>> @@ -406,7 +406,8 @@ struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc, >>> const struct of_phandle_args *args); >>> >>> struct pwm_device *pwm_get(struct device *dev, const char *con_id); >>> -struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id); >>> +struct pwm_device *of_pwm_get(struct device *dev, struct device_node *np, >>> + const char *con_id); >> >> I'm slightly concerned about this. I think one of the reasons why this >> was introduced was to allow code to get at the PWM if they didn't have >> a struct device * available. However, it doesn't seem like there are any >> users of that function, so this seems fine. > > The git blame pointed out commit 8eb961279960: > " > pwm: core: Rename of_pwm_request() to of_pwm_get() and export it > > Allow client driver to use of_pwm_get() to get the PWM they need. This > is needed for drivers which handle more than one PWM separately, like > leds-pwm driver, which have: > " > ... > > For instance, I tested the leds-pwm driver. It uses the devm_* variant > now (as others), there is a struct device * available. So yes, it seems > fine. > > The only thing maybe out of tree code? This is where I have a doubt on > having a mandatory struct device * to enforce consumer link creation... > or make it optional (e.g. behave as a 'legacy' API) and warn the caller. > > Please let me know your feeling. Hi Thierry, I just sent a v4 to update the error handling following the cases described above. BR, Fabrice > Best regards, > Fabrice > >> >> Thierry >> >>> void pwm_put(struct pwm_device *pwm); >>> >>> struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id); >>> @@ -494,7 +495,8 @@ static inline struct pwm_device *pwm_get(struct device *dev, >>> return ERR_PTR(-ENODEV); >>> } >>> >>> -static inline struct pwm_device *of_pwm_get(struct device_node *np, >>> +static inline struct pwm_device *of_pwm_get(struct device *dev, >>> + struct device_node *np, >>> const char *con_id) >>> { >>> return ERR_PTR(-ENODEV); >>> -- >>> 1.9.1 >>>
