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    SubjectRe: [PATCH 01/11] firmware: arm_scmi: review protocol registration interface
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    Hi Cristian,

    Thanks for this series!

    On 10/14/20 11:05 AM, Cristian Marussi wrote:
    > Extend common protocol registration routines and provide some new generic
    > protocols' init/deinit helpers that tracks protocols' users and automatically
    > perform the proper initialization/de-initialization on demand.
    >
    > Convert all protocols to use new registration schema while modifying only Base
    > protocol to use also the new initialization helpers.
    >
    > All other standard protocols' initialization is still umodified and bound to
    > SCMI devices probing.
    >
    > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
    > ---
    > drivers/firmware/arm_scmi/base.c | 10 +-
    > drivers/firmware/arm_scmi/bus.c | 61 +++++++---
    > drivers/firmware/arm_scmi/clock.c | 10 +-
    > drivers/firmware/arm_scmi/common.h | 31 ++++-
    > drivers/firmware/arm_scmi/driver.c | 168 +++++++++++++++++++++++++++-
    > drivers/firmware/arm_scmi/notify.c | 3 +-
    > drivers/firmware/arm_scmi/perf.c | 10 +-
    > drivers/firmware/arm_scmi/power.c | 10 +-
    > drivers/firmware/arm_scmi/reset.c | 10 +-
    > drivers/firmware/arm_scmi/sensors.c | 10 +-
    > drivers/firmware/arm_scmi/system.c | 8 +-
    > include/linux/scmi_protocol.h | 6 +-
    > 12 files changed, 298 insertions(+), 39 deletions(-)
    >
    > diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
    > index 017e5d8bd869..f19e08ed4369 100644
    > --- a/drivers/firmware/arm_scmi/base.c
    > +++ b/drivers/firmware/arm_scmi/base.c
    > @@ -318,7 +318,7 @@ static const struct scmi_event_ops base_event_ops = {
    > .fill_custom_report = scmi_base_fill_custom_report,
    > };
    >
    > -int scmi_base_protocol_init(struct scmi_handle *h)
    > +static int scmi_base_protocol_init(struct scmi_handle *h)
    > {
    > int id, ret;
    > u8 *prot_imp;
    > @@ -365,3 +365,11 @@ int scmi_base_protocol_init(struct scmi_handle *h)
    >
    > return 0;
    > }
    > +
    > +static struct scmi_protocol scmi_base = {
    > + .id = SCMI_PROTOCOL_BASE,
    > + .init = &scmi_base_protocol_init,
    > + .ops = NULL,
    > +};
    > +
    > +DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(base, scmi_base)
    > diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
    > index 1377ec76a45d..afa2e4818a2b 100644
    > --- a/drivers/firmware/arm_scmi/bus.c
    > +++ b/drivers/firmware/arm_scmi/bus.c
    > @@ -16,7 +16,7 @@
    > #include "common.h"
    >
    > static DEFINE_IDA(scmi_bus_id);
    > -static DEFINE_IDR(scmi_protocols);
    > +static DEFINE_IDR(scmi_available_protocols);
    > static DEFINE_SPINLOCK(protocol_lock);
    >
    > static const struct scmi_device_id *
    > @@ -51,13 +51,29 @@ static int scmi_dev_match(struct device *dev, struct device_driver *drv)
    > return 0;
    > }
    >
    > +const struct scmi_protocol *scmi_get_protocol(int protocol_id)
    > +{
    > + const struct scmi_protocol *proto;
    > +
    > + proto = idr_find(&scmi_available_protocols, protocol_id);
    > + if (!proto) {
    > + pr_warn("SCMI Protocol 0x%x not found!\n", protocol_id);
    > + return NULL;
    > + }
    > +
    > + pr_debug("GOT SCMI Protocol 0x%x\n", protocol_id);
    > +
    > + return proto;
    > +}
    > +
    > static int scmi_protocol_init(int protocol_id, struct scmi_handle *handle)
    > {
    > - scmi_prot_init_fn_t fn = idr_find(&scmi_protocols, protocol_id);
    > + const struct scmi_protocol *proto;
    >
    > - if (unlikely(!fn))
    > + proto = idr_find(&scmi_available_protocols, protocol_id);
    > + if (!proto)
    > return -EINVAL;


    Any reason not to use the above scmi_get_protocol here ?

    > - return fn(handle);
    > + return proto->init(handle);
    > }
    >
    > static int scmi_protocol_dummy_init(struct scmi_handle *handle)
    > @@ -84,7 +100,7 @@ static int scmi_dev_probe(struct device *dev)
    > return ret;
    >
    > /* Skip protocol initialisation for additional devices */
    > - idr_replace(&scmi_protocols, &scmi_protocol_dummy_init,
    > + idr_replace(&scmi_available_protocols, &scmi_protocol_dummy_init,
    > scmi_dev->protocol_id);
    >
    > return scmi_drv->probe(scmi_dev);
    > @@ -194,26 +210,45 @@ void scmi_set_handle(struct scmi_device *scmi_dev)
    > scmi_dev->handle = scmi_handle_get(&scmi_dev->dev);
    > }
    >
    > -int scmi_protocol_register(int protocol_id, scmi_prot_init_fn_t fn)
    > +int scmi_protocol_register(struct scmi_protocol *proto)
    > {
    > int ret;
    >
    > + if (!proto) {
    > + pr_err("invalid protocol\n");
    > + return -EINVAL;
    > + }
    > +
    > + if (!proto->init) {
    > + pr_err("missing .init() for protocol 0x%x\n", proto->id);
    > + return -EINVAL;
    > + }
    > +
    > spin_lock(&protocol_lock);
    > - ret = idr_alloc(&scmi_protocols, fn, protocol_id, protocol_id + 1,
    > - GFP_ATOMIC);
    > + ret = idr_alloc(&scmi_available_protocols, proto,
    > + proto->id, proto->id + 1, GFP_ATOMIC);
    > spin_unlock(&protocol_lock);
    > - if (ret != protocol_id)
    > - pr_err("unable to allocate SCMI idr slot, err %d\n", ret);
    > + if (ret != proto->id) {
    > + pr_err("unable to allocate SCMI idr slot for 0x%x - err %d\n",
    > + proto->id, ret);
    > + return ret;
    > + }
    > +
    > + pr_debug("Registered SCMI Protocol 0x%x\n", proto->id);
    >
    > - return ret;
    > + return 0;
    > }
    > EXPORT_SYMBOL_GPL(scmi_protocol_register);
    >
    > -void scmi_protocol_unregister(int protocol_id)
    > +void scmi_protocol_unregister(const struct scmi_protocol *proto)
    > {
    > spin_lock(&protocol_lock);
    > - idr_remove(&scmi_protocols, protocol_id);
    > + idr_remove(&scmi_available_protocols, proto->id);
    > spin_unlock(&protocol_lock);
    > +
    > + pr_debug("Unregistered SCMI Protocol 0x%x\n", proto->id);
    > +
    > + return;
    > }
    > EXPORT_SYMBOL_GPL(scmi_protocol_unregister);
    >

    [...]

    > diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
    > index 3dfd8b6a0ebf..7de994e49884 100644
    > --- a/drivers/firmware/arm_scmi/driver.c
    > +++ b/drivers/firmware/arm_scmi/driver.c
    > @@ -23,6 +23,7 @@
    > #include <linux/of_address.h>
    > #include <linux/of_device.h>
    > #include <linux/processor.h>
    > +#include <linux/refcount.h>
    > #include <linux/slab.h>
    >
    > #include "common.h"
    > @@ -68,6 +69,21 @@ struct scmi_xfers_info {
    > spinlock_t xfer_lock;
    > };
    >
    > +/**
    > + * struct scmi_protocol_instance - Describe an initialized protocol instance.
    > + * @proto: A reference to the protocol descriptor.
    > + * @gid: A reference for per-protocol devres management.
    > + * @users: A refcount to track effective users of this protocol.
    > + *
    > + * Each protocol is initialized independently once for each SCMI platform in
    > + * which is defined by DT and implemented by the SCMI server fw.
    > + */
    > +struct scmi_protocol_instance {
    > + const struct scmi_protocol *proto;
    > + void *gid;
    > + refcount_t users;
    > +};
    > +
    > /**
    > * struct scmi_info - Structure representing a SCMI instance
    > *
    > @@ -80,6 +96,10 @@ struct scmi_xfers_info {
    > * @rx_minfo: Universal Receive Message management info
    > * @tx_idr: IDR object to map protocol id to Tx channel info pointer
    > * @rx_idr: IDR object to map protocol id to Rx channel info pointer
    > + * @protocols: An array of protocols' instance descriptors initialized for
    > + * this SCMI instance: populated on protocol's first attempted
    > + * usage.
    > + * @protocols_mtx: A mutex to protect protocols instances initialization.
    > * @protocols_imp: List of protocols implemented, currently maximum of
    > * MAX_PROTOCOLS_IMP elements allocated by the base protocol
    > * @node: List head
    > @@ -94,6 +114,9 @@ struct scmi_info {
    > struct scmi_xfers_info rx_minfo;
    > struct idr tx_idr;
    > struct idr rx_idr;
    > + struct scmi_protocol_instance *protocols[SCMI_MAX_PROTO];
    > + /* Ensure mutual exclusive access to protocols instance array */
    > + struct mutex protocols_mtx;
    > u8 *protocols_imp;
    > struct list_head node;
    > int users;
    > @@ -519,6 +542,132 @@ int scmi_version_get(const struct scmi_handle *handle, u8 protocol,
    > return ret;
    > }
    >
    > +/**
    > + * scmi_get_protocol_instance - Protocol initialization helper.
    > + * @handle: A reference to the SCMI platform instance.
    > + * @protocol_id: The protocol being requested.
    > + *
    > + * In case the required protocol has never been requested before for this
    > + * instance, allocate and initialize all the needed structures while handling
    > + * resource allocation with a dedicated per-protocol devres subgroup.
    > + *
    > + * Return: A reference to an initialized protocol instance or error on failure.
    > + */
    > +static struct scmi_protocol_instance * __must_check
    > +scmi_get_protocol_instance(struct scmi_handle *handle, u8 protocol_id)
    > +{
    > + int ret = -ENOMEM;
    > + void *gid;
    > + struct scmi_protocol_instance *pi;
    > + struct scmi_info *info = handle_to_scmi_info(handle);
    > +
    > + mutex_lock(&info->protocols_mtx);
    > + /* Ensure protocols has been updated */
    > + smp_rmb();
    > + pi = info->protocols[protocol_id];
    > +
    > + if (!pi) {
    > + const struct scmi_protocol *proto;
    > +
    > + /* Fail if protocol not registered on bus */
    > + proto = scmi_get_protocol(protocol_id);
    > + if (!proto) {
    > + ret = -EINVAL;
    > + goto out;
    > + }
    > +
    > + /* Protocol specific devres group */
    > + gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
    > + if (!gid)
    > + goto out;
    > +
    > + pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
    > + if (!pi)
    > + goto clean;
    > +
    > + pi->gid = gid;
    > + pi->proto = proto;
    > + refcount_set(&pi->users, 1);
    > + /* proto->init is assured NON NULL by scmi_protocol_register */
    > + ret = pi->proto->init(handle);

    Isnt this already done in scmi_protocol_init? Or rather the init should
    remain here and there is no need for it to be called from
    scmi_protocol_init?



    --
    Warm Regards
    Thara

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