Re: [PATCH v6 37/37] firmware: arm_scmi: add dynamic scmi devices creation

Sudeep Holla
2021-03-15T08:34:38Z

Hi Cristian,

Sorry for the delay.

On Tue, Feb 02, 2021 at 10:15:55PM +0000, Cristian Marussi wrote:
> Having added the support for SCMI protocols as modules in order to let
> vendors extend the SCMI core with their own additions it seems odd to
> then force SCMI drivers built on top to use a static device table to
> declare their devices since this way any new SCMI drivers addition
> would need the core SCMI device table to be updated too.
>
> Remove the static core device table and let SCMI drivers to simply declare
> which device/protocol pair they need at initialization time: the core will
> then take care to generate such devices dynamically during platform
> initialization or at module loading time, as long as the requested
> underlying protocol is defined in the DT.
>
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> ---
> v4 --> v5
> - using klist instead of custom lists
> v3 --> v4
> - add a few comments
> ---
> drivers/firmware/arm_scmi/bus.c | 30 +++
> drivers/firmware/arm_scmi/common.h | 5 +
> drivers/firmware/arm_scmi/driver.c | 309 +++++++++++++++++++++++++----
> 3 files changed, 310 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
> index 88e5057f4e85..88149a46e6d9 100644
> --- a/drivers/firmware/arm_scmi/bus.c
> +++ b/drivers/firmware/arm_scmi/bus.c
> @@ -51,6 +51,31 @@ static int scmi_dev_match(struct device *dev, struct device_driver *drv)
> return 0;
> }
>
> +static int scmi_match_by_id_table(struct device *dev, void *data)
> +{
> + struct scmi_device *sdev = to_scmi_dev(dev);
> + struct scmi_device_id *id_table = data;
> +
> + return sdev->protocol_id == id_table->protocol_id &&
> + !strcmp(sdev->name, id_table->name);
> +}
> +
> +struct scmi_device *scmi_find_child_dev(struct device *parent,
> + int prot_id, const char *name)
> +{
> + struct scmi_device_id id_table;
> + struct device *dev;
> +
> + id_table.protocol_id = prot_id;
> + id_table.name = name;
> +
> + dev = device_find_child(parent, &id_table, scmi_match_by_id_table);
> + if (!dev)
> + return NULL;
> +
> + return to_scmi_dev(dev);
> +}
> +
> const struct scmi_protocol *scmi_get_protocol(int protocol_id)
> {
> const struct scmi_protocol *proto;
> @@ -114,6 +139,10 @@ int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
> {
> int retval;
>
> + retval = scmi_request_protocol_device(driver->id_table);
> + if (retval)
> + return retval;
> +
> driver->driver.bus = &scmi_bus_type;
> driver->driver.name = driver->name;
> driver->driver.owner = owner;
> @@ -130,6 +159,7 @@ EXPORT_SYMBOL_GPL(scmi_driver_register);
> void scmi_driver_unregister(struct scmi_driver *driver)
> {
> driver_unregister(&driver->driver);
> + scmi_unrequest_protocol_device(driver->id_table);
> }
> EXPORT_SYMBOL_GPL(scmi_driver_unregister);
>
> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> index 1e2046c61d43..9a0519db4865 100644
> --- a/drivers/firmware/arm_scmi/common.h
> +++ b/drivers/firmware/arm_scmi/common.h
> @@ -307,6 +307,11 @@ struct scmi_transport_ops {
> bool (*poll_done)(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer);
> };
>
> +int scmi_request_protocol_device(const struct scmi_device_id *id_table);
> +void scmi_unrequest_protocol_device(const struct scmi_device_id *id_table);

Sorry for being pedantic, I don't like these names. I would prefer
something like scmi_protocol_device_{create,destroy/delete}_request.
The action the function does needs to be at the end of the function name.
Atleast that is something I follow. I haven't checked all the previous
patches, just this function made to look at both the name style and the
name itself.

> +struct scmi_device *scmi_find_child_dev(struct device *parent,
> + int prot_id, const char *name);
> +

scmi_child_dev_find based on what I mentioned above. Please change all
other non-static functions even if I have not mentioned. Try to cover
all the new functions introduced in this series, existing ones we can
take up later.

> /**
> * struct scmi_desc - Description of SoC integration
> *
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index dcdfd94b47f7..9fc979e3b16f 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -21,6 +21,7 @@
> #include <linux/io.h>
> #include <linux/kernel.h>
> #include <linux/ktime.h>
> +#include <linux/list.h>
> #include <linux/module.h>
> #include <linux/of_address.h>
> #include <linux/of_device.h>
> @@ -56,6 +57,14 @@ static DEFINE_MUTEX(scmi_list_mutex);
> /* Track the unique id for the transfers for debug & profiling purpose */
> static atomic_t transfer_last_id;
>
> +static DEFINE_IDR(scmi_requested_devices);
> +static DEFINE_MUTEX(scmi_requested_devices_mtx);
> +
> +struct scmi_requested_dev {
> + const struct scmi_device_id *id_table;
> + struct list_head node;
> +};
> +
> /**
> * struct scmi_xfers_info - Structure to manage transfer information
> *
> @@ -113,6 +122,8 @@ struct scmi_protocol_instance {
> * @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
> + * @active_protocols: IDR storing device_nodes for protocols actually defined
> + * in the DT and confirmed as implemented by fw.
> * @notify_priv: Pointer to private data structure specific to notifications.
> * @node: List head
> * @users: Number of users of this instance
> @@ -130,6 +141,7 @@ struct scmi_info {
> /* Ensure mutual exclusive access to protocols instance array */
> struct mutex protocols_mtx;
> u8 *protocols_imp;
> + struct idr active_protocols;
> void *notify_priv;
> struct list_head node;
> int users;
> @@ -936,6 +948,13 @@ static void scmi_devm_put_protocol(struct scmi_device *sdev, u8 protocol_id)
> WARN_ON(ret);
> }
>
> +static inline
> +struct scmi_handle *scmi_handle_get_from_info(struct scmi_info *info)
> +{
> + info->users++;

Doesn't it race with anything ? I have already forgotten how this is used
and in what context this gets called.

> + return &info->handle;
> +}
> +
> /**
> * scmi_handle_get() - Get the SCMI handle for a device
> *
> @@ -957,8 +976,7 @@ struct scmi_handle *scmi_handle_get(struct device *dev)
> list_for_each(p, &scmi_list) {
> info = list_entry(p, struct scmi_info, node);
> if (dev->parent == info->dev) {
> - handle = &info->handle;
> - info->users++;
> + handle = scmi_handle_get_from_info(info);

Ah here it is. Any particular reasons for moving it to separate function ?

--
Regards,
Sudeep