Re: [PATCH v2 3/8] firmware: arm_scmi: introduce new protocol operations support

[Thara Gopinath <thara.gopinath@linaro.org>]

Hi Cristian,

On 10/28/20 4:29 PM, Cristian Marussi wrote:
> Expose a new generic get/put protocols API based on protocol handles;
> provide also a devres managed version also for notifications.

minor nit.. Maybe yous should reword this! Kind of confusing to understand!

Also, if it was me, I will separate the notifications and get/put hooks
into two separate patches. Not an issue though if you want to keep it
in the same patch.

> All SCMI drivers still keep using the old handle based interface.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> ---
>   drivers/firmware/arm_scmi/driver.c | 126 +++++++++++++++++++++++++++++
>   drivers/firmware/arm_scmi/notify.c | 123 ++++++++++++++++++++++++++++
>   include/linux/scmi_protocol.h      |  34 +++++++-
>   3 files changed, 282 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 8ca04acb6abb..4d86aafbf465 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -15,6 +15,7 @@
>    */
>   
>   #include <linux/bitmap.h>
> +#include <linux/device.h>
>   #include <linux/export.h>
>   #include <linux/idr.h>
>   #include <linux/io.h>
> @@ -728,6 +729,38 @@ void scmi_release_protocol(struct scmi_handle *handle, u8 protocol_id)
>   	mutex_unlock(&info->protocols_mtx);
>   }
>   
> +/**
> + * scmi_get_protocol_operations  - Get protocol operations
> + * @handle: A reference to the SCMI platform instance.
> + * @protocol_id: The protocol being requested.
> + * @ph: A pointer reference used to pass back the associated protocol handle.
> + *
> + * Get hold of a protocol accounting for its usage, eventually triggering its
> + * initialization, and returning the protocol specific operations and related
> + * protocol handle which will be used as first argument in most of the protocols
> + * operations methods.
> + *
> + * Return: A reference to the requested protocol operations or error.
> + *	   Must be checked for errors by caller.
> + */
> +static const void __must_check *
> +scmi_get_protocol_operations(struct scmi_handle *handle, u8 protocol_id,
> +			     struct scmi_protocol_handle **ph)
> +{
> +	struct scmi_protocol_instance *pi;
> +
> +	if (!ph)
> +		return ERR_PTR(-EINVAL);
> +
> +	pi = scmi_get_protocol_instance(handle, protocol_id);
> +	if (IS_ERR(pi))
> +		return pi;
> +
> +	*ph = &pi->ph;
> +
> +	return pi->proto->ops;
> +}
> +
>   void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
>   				     u8 *prot_imp)
>   {
> @@ -751,6 +784,95 @@ scmi_is_protocol_implemented(const struct scmi_handle *handle, u8 prot_id)
>   	return false;
>   }
>   
> +struct scmi_protocol_devres {
> +	struct scmi_handle *handle;
> +	u8 protocol_id;
> +};
> +
> +static void scmi_devm_release_protocol(struct device *dev, void *res)
> +{
> +	struct scmi_protocol_devres *dres = res;
> +
> +	scmi_release_protocol(dres->handle, dres->protocol_id);
> +}
> +
> +/**
> + * scmi_devm_get_protocol_ops  - Devres managed get protocol operations
> + * @sdev: A reference to an scmi_device whose embedded struct device is to
> + *	  be used for devres accounting.
> + * @protocol_id: The protocol being requested.
> + * @ph: A pointer reference used to pass back the associated protocol handle.
> + *
> + * Get hold of a protocol accounting for its usage, eventually triggering its
> + * initialization, and returning the protocol specific operations and related
> + * protocol handle which will be used as first argument in most of the
> + * protocols operations methods.
> + * Being a devres based managed method, protocol hold will be automatically
> + * released, and possibly de-initialized on last user, once the SCMI driver
> + * owning the scmi_device is unbound from it.
> + *
> + * Return: A reference to the requested protocol operations or error.
> + *	   Must be checked for errors by caller.
> + */
> +static const void __must_check *
> +scmi_devm_get_protocol_ops(struct scmi_device *sdev, u8 protocol_id,
> +			   struct scmi_protocol_handle **ph)
> +{
> +	struct scmi_protocol_instance *pi;
> +	struct scmi_protocol_devres *dres;
> +	struct scmi_handle *handle = sdev->handle;
> +
> +	if (!ph)
> +		return ERR_PTR(-EINVAL);
> +
> +	dres = devres_alloc(scmi_devm_release_protocol,
> +			    sizeof(*dres), GFP_KERNEL);
> +	if (!dres)
> +		return ERR_PTR(-ENOMEM);
> +
> +	pi = scmi_get_protocol_instance(handle, protocol_id);
> +	if (IS_ERR(pi)) {
> +		devres_free(dres);
> +		return pi;
> +	}
> +
> +	dres->handle = handle;
> +	dres->protocol_id = protocol_id;
> +	devres_add(&sdev->dev, dres);
> +
> +	*ph = &pi->ph;
> +
> +	return pi->proto->ops;
> +}
> +
> +static int scmi_devm_protocol_match(struct device *dev, void *res, void *data)
> +{
> +	struct scmi_protocol_devres *dres = res;
> +
> +	if (WARN_ON(!dres || !data))
> +		return 0;
> +
> +	return dres->protocol_id == *((u8 *)data);
> +}
> +
> +/**
> + * scmi_devm_put_protocol_ops  - Devres managed put protocol operations
> + * @sdev: A reference to an scmi_device whose embedded struct device is to
> + *	  be used for devres accounting.
> + * @protocol_id: The protocol being requested.
> + *
> + * Explicitly release a protocol hold previously obtained calling the above
> + * @scmi_devm_get_protocol_ops.
> + */
> +static void scmi_devm_put_protocol_ops(struct scmi_device *sdev, u8 protocol_id)
> +{
> +	int ret;
> +
> +	ret = devres_release(&sdev->dev, scmi_devm_release_protocol,
> +			     scmi_devm_protocol_match, &protocol_id);
> +	WARN_ON(ret);
> +}
> +
>   /**
>    * scmi_handle_get() - Get the SCMI handle for a device
>    *
> @@ -1004,6 +1126,10 @@ static int scmi_probe(struct platform_device *pdev)
>   	handle = &info->handle;
>   	handle->dev = info->dev;
>   	handle->version = &info->version;
> +	handle->devm_get_ops = scmi_devm_get_protocol_ops;
> +	handle->devm_put_ops = scmi_devm_put_protocol_ops;
> +	handle->get_ops = scmi_get_protocol_operations;
> +	handle->put_ops = scmi_release_protocol;

Why do you need a dev_res version and a non dev_res version? I checked
patch 6 where you convert the drivers to use these hooks and all of them
are using the dev res apis.

>   
>   	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
>   	if (ret)
> diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
> index eae58b2a92cc..64d43e425644 100644
> --- a/drivers/firmware/arm_scmi/notify.c
> +++ b/drivers/firmware/arm_scmi/notify.c
> @@ -1370,6 +1370,127 @@ static int scmi_unregister_notifier(const struct scmi_handle *handle,
>   	return 0;
>   }
>   
> +struct scmi_notifier_devres {
> +	const struct scmi_handle *handle;
> +	u8 proto_id;
> +	u8 evt_id;
> +	u32 __src_id;
> +	u32 *src_id;

Instead of maintaining two separate pointers for src id,
why not define a bool, something like is_src_id_valid?
Should simply this a bit and also don't have to maintain two 32 bit 
pointers. What do you think?

> +	struct notifier_block *nb;
> +};
> +
> +static void scmi_devm_release_notifier(struct device *dev, void *res)
> +{
> +	struct scmi_notifier_devres *dres = res;
> +
> +	scmi_unregister_notifier(dres->handle, dres->proto_id, dres->evt_id,
> +				 dres->src_id, dres->nb);
> +}
> +
> +/**
> + * scmi_devm_register_notifier()  - Managed registration of a notifier_block
> + * for an event
> + * @sdev: A reference to an scmi_device whose embedded struct device is to
> + *	  be used for devres accounting.
> + * @proto_id: Protocol ID
> + * @evt_id: Event ID
> + * @src_id: Source ID, when NULL register for events coming form ALL possible
> + *	    sources
> + * @nb: A standard notifier block to register for the specified event
> + *
> + * Generic devres managed helper to register a notifier_block against a
> + * protocol event.
> + */
> +static int scmi_devm_register_notifier(struct scmi_device *sdev,
> +				       u8 proto_id, u8 evt_id, u32 *src_id,
> +				       struct notifier_block *nb)
> +{
> +	int ret;
> +	struct scmi_notifier_devres *dres;
> +
> +	dres = devres_alloc(scmi_devm_release_notifier,
> +			    sizeof(*dres), GFP_KERNEL);
> +	if (!dres)
> +		return -ENOMEM;
> +
> +	ret = scmi_register_notifier(sdev->handle, proto_id,
> +				     evt_id, src_id, nb);
> +	if (ret) {
> +		devres_free(dres);
> +		return ret;
> +	}
> +
> +	dres->handle = sdev->handle;
> +	dres->proto_id = proto_id;
> +	dres->evt_id = evt_id;
> +	dres->nb = nb;
> +	if (src_id) {
> +		dres->__src_id = *src_id;
> +		dres->src_id = &dres->__src_id;
> +	} else {
> +		dres->src_id = NULL;
> +	}
> +	devres_add(&sdev->dev, dres);
> +
> +	return ret;
> +}
> +
> +static int scmi_devm_notifier_match(struct device *dev, void *res, void *data)
> +{
> +	struct scmi_notifier_devres *dres = res;
> +	struct scmi_notifier_devres *xres = data;
> +
> +	if (WARN_ON(!dres || !xres))
> +		return 0;
> +
> +	return dres->proto_id == xres->proto_id &&
> +		dres->evt_id == xres->evt_id &&
> +		dres->nb == xres->nb &&

Does the nb have to be compared as well ?

> +		((!dres->src_id && !xres->src_id) ||
> +		  (dres->src_id && xres->src_id &&
> +		   dres->__src_id == xres->__src_id));


-- 
Warm Regards
Thara