Re: [PATCH v14 07/32] firmware: arm_scmi: Add Telemetry basic attributes enumeration

[Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>]

On Fri, 16 Oct 2026 19:55:28 +0100
Cristian Marussi <cristian.marussi@arm.com> wrote:

> Add SCMIv4.0 Telemetry basic support for minimal initialization and
> protocol attributes enumeration: expose telemetry instance descriptor
> via a simple information retrieval protocol operation.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>

A few minor comments but nothing I care strongly about.
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

>  #endif /* _SCMI_PROTOCOLS_H */
> diff --git a/drivers/firmware/arm_scmi/telemetry.c b/drivers/firmware/arm_scmi/telemetry.c
> new file mode 100644
> index 000000000000..32f6f8d1106d
> --- /dev/null
> +++ b/drivers/firmware/arm_scmi/telemetry.c
> @@ -0,0 +1,148 @@

> +
> +enum scmi_telemetry_protocol_cmd {

Perhaps add a comment on enum scmi_common_cmd containing additional values
that apply to telemetry.

> +	TELEMETRY_LIST_SHMTI = 0x3,

> +
> +struct telemetry_info {
> +	bool streaming_mode;

I'd bring fields of internal tracking structures in only when
they are used (even if that is just setting them).

> +	unsigned int num_shmti;
> +	unsigned int num_des_tstamp;
> +	unsigned int default_blk_ts_rate;
> +	const struct scmi_protocol_handle *ph;
> +	struct scmi_telemetry_info info;
> +};
> +
> +static int
> +scmi_telemetry_protocol_attributes_get(struct telemetry_info *ti)
> +{
> +	struct scmi_msg_resp_telemetry_protocol_attributes *resp;
> +	const struct scmi_protocol_handle *ph = ti->ph;
> +	struct scmi_xfer *t;
> +	int ret;
> +
> +	ret = ph->xops->xfer_get_init(ph, PROTOCOL_ATTRIBUTES, 0,
> +				      sizeof(*resp), &t);
> +	if (ret)
> +		return ret;
> +
> +	resp = t->rx.buf;
> +	ret = ph->xops->do_xfer(ph, t);
> +	if (!ret) {
> +		__le32 attr = resp->attributes_1;
> +		__be32 de_impl_version[SCMI_TLM_DE_IMPL_NUM_DWORDS];
> +

> +		for (int i = 0; i < SCMI_TLM_DE_IMPL_NUM_DWORDS; i++)
> +			de_impl_version[i] =
> +				cpu_to_be32(le32_to_cpu(resp->de_implem_rev_dword[i]));

That dance is a swap as data is stored le but UUID fields are be.
Maybe going via cpu endian is fine as would be silly to have le32_to_be32()
so it perhaps has documentation value.  Fair enough - I argued myself around
with agreeing with how you did it here, but left the discussion for anyone
else who has similar thoughts.

> +		import_uuid(&ti->info.base.primary_revision, (const __u8 *)&de_impl_version);
> +		ti->info.single_read_support = SUPPORTS_SINGLE_READ(attr);
> +		ti->info.continuous_update_support = SUPPORTS_CONTINUOS_UPDATE(attr);
> +		ti->info.per_group_config_support = SUPPORTS_PER_GROUP_CONFIG(attr);
> +		ti->info.reset_support = SUPPORTS_RESET(attr);
> +		ti->info.fc_support = SUPPORTS_FC(attr);
> +		ti->num_shmti = le32_get_bits(attr, GENMASK(15, 0));
> +		ti->default_blk_ts_rate = le32_to_cpu(resp->default_blk_ts_rate);
> +	}
> +
> +	ph->xops->xfer_put(ph, t);
> +
> +	return ret;
> +}

> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index 5ab73b1ab9aa..121c83e1c6d8 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h

...


> +/**
> + * struct scmi_telemetry_proto_ops - represents the various operations provided
> + *	by SCMI Telemetry Protocol
> + *
> + * @info_get: get the general Telemetry information.
> + */
> +struct scmi_telemetry_proto_ops {
info> +	const struct scmi_telemetry_info __must_check *(*info_get)
> +		(const struct scmi_protocol_handle *ph);

Why __must_check?  Be a bit crazy if no one did anything with the
info they just requested, so that seems overkill and doesn't help with
the long line.

> +};
> +