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Message-ID: <20251017163725.0000149e@huawei.com>
Date: Fri, 17 Oct 2025 16:37:25 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Cristian Marussi <cristian.marussi@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
<arm-scmi@...r.kernel.org>, <sudeep.holla@....com>,
<james.quinlan@...adcom.com>, <f.fainelli@...il.com>,
<vincent.guittot@...aro.org>, <etienne.carriere@...com>,
<peng.fan@....nxp.com>, <michal.simek@....com>, <quic_sibis@...cinc.com>,
<dan.carpenter@...aro.org>, <d-gole@...com>, <souvik.chakravarty@....com>
Subject: Re: [PATCH 05/10] firmware: arm_scmi: Add Telemetry protocol
support
On Thu, 25 Sep 2025 21:35:49 +0100
Cristian Marussi <cristian.marussi@....com> wrote:
> Add basic support for SCMI V4.0-alpha_0 Telemetry protocol including SHMTI,
> FastChannels, Notifications and Single Sample Reads collection methods.
>
> Signed-off-by: Cristian Marussi <cristian.marussi@....com>
Hi,
This is very much in the superficial drive by category as reviews
go. A few things noted but I've not looked at the code in enough
detail.
Jonathan
> diff --git a/drivers/firmware/arm_scmi/telemetry.c b/drivers/firmware/arm_scmi/telemetry.c
> new file mode 100644
> index 000000000000..f03000c173c2
> --- /dev/null
> +++ b/drivers/firmware/arm_scmi/telemetry.c
> @@ -0,0 +1,2117 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * System Control and Management Interface (SCMI) Telemetry Protocol
> + *
> + * Copyright (C) 2025 ARM Ltd.
> + *
My favorite trivial comment applies. What does this blank line add
to readability? I'd drop it.
> + */
> +
> +struct scmi_de_desc {
> + __le32 id;
> + __le32 grp_id;
> + __le32 data_sz;
> + __le32 attr_1;
> +#define IS_NAME_SUPPORTED(d) ((d)->attr_1 & BIT(31))
> +#define IS_FC_SUPPORTED(d) ((d)->attr_1 & BIT(30))
> +#define GET_DE_TYPE(d) (le32_get_bits((d)->attr_1, GENMASK(29, 22)))
> +#define IS_PERSISTENT(d) ((d)->attr_1 & BIT(21))
> +#define GET_DE_UNIT_EXP(d) \
> + ({ \
> + int __signed_exp = \
> + le32_get_bits((d)->attr_1, GENMASK(20, 13)); \
> + \
> + if (__signed_exp & BIT(7)) \
> + __signed_exp |= GENMASK(31, 8); \
> + __signed_exp; \
> + })
> +#define GET_DE_UNIT(d) (le32_get_bits((d)->attr_1, GENMASK(12, 5)))
> +
> +#define GET_DE_TSTAMP_EXP(d) \
> + ({ \
> + int __signed_exp = \
> + FIELD_GET(GENMASK(4, 1), (d)->attr_1); \
> + \
> + if (__signed_exp & BIT(3)) \
> + __signed_exp |= GENMASK(31, 4); \
> + __signed_exp; \
See below for sign_extend32() using code to replace these.
> +
> +struct scmi_msg_resp_telemetry_reading_complete {
> + __le32 num_dwords;
> + __le32 dwords[];
__counted_by(num_word);
> +};
> +
> +/* TDCF */
> +
> +#define TO_CPU_64(h, l) (((u64)le32_to_cpu((h)) << 32) | le32_to_cpu((l)))
Some of this stuff sounds very generic and isn't at all.
Personally I think I'd just drop this one as it may be better to see
the implementation wherever it is used.
> +static int scmi_telemetry_tdcf_line_parse(struct telemetry_info *ti,
> + struct payload __iomem *payld,
> + struct telemetry_shmti *shmti,
> + bool update)
> +{
> + int used_qwords;
> +
> + used_qwords = (USE_LINE_TS(payld) && TS_VALID(payld)) ?
> + QWORDS_TS_LINE_DATA_PAYLD : QWORDS_LINE_DATA_PAYLD;
> +
> + /*Invalid lines are not an error, could simply be disabled DEs */
Check for inconsistent comment syntax etc.
> + if (DATA_INVALID(payld))
> + return used_qwords;
> +
> +static int scmi_telemetry_shmti_scan(struct telemetry_info *ti,
> + unsigned int shmti_id, u64 ts,
> + bool update)
> +{
> + struct telemetry_shmti *shmti = &ti->shmti[shmti_id];
> + struct tdcf __iomem *tdcf = shmti->base;
> + int retries = SCMI_TLM_TDCF_MAX_RETRIES;
> + u64 startm = 0, endm = 0xffffffffffffffff;
No one likes counting fs. Use a GENMASK probably.
> + void *eplg = SHMTI_EPLG(shmti);
> +static void
> +scmi_telemetry_msg_payld_process(struct telemetry_info *ti,
> + unsigned int num_dwords, unsigned int *dwords,
I'd kind of expect something called dwords to have a fixed size. u32, u64 or
whatever.
> + ktime_t timestamp)
> +{
> + u32 next = 0;
> +
> + while (next < num_dwords) {
> + struct payload *payld = (struct payload *)&dwords[next];
> + struct scmi_telemetry_de *de;
> + struct telemetry_de *tde;
> + u32 de_id;
> +
> + next += USE_LINE_TS(payld) ?
> + TS_LINE_DATA_PAYLD_WORDS : LINE_DATA_PAYLD_WORDS;
> +
> + if (DATA_INVALID(payld)) {
> + dev_err(ti->dev, "MSG - Received INVALID DATA line\n");
> + continue;
> + }
> +
> + de_id = le32_to_cpu(payld->id);
> + de = xa_load(&ti->xa_des, de_id);
> + if (!de || !de->enabled) {
> + dev_err(ti->dev,
> + "MSG - Received INVALID DE - ID:%u enabled:%d\n",
> + de_id, de ? (de->enabled ? 'Y' : 'N') : 'X');
> + continue;
> + }
> +
> + tde = to_tde(de);
> + guard(mutex)(&tde->mtx);
> + tde->cached = true;
> + tde->last_val = LINE_DATA_GET(&payld->tsl);
> + //TODO BLK_TS in notification payloads
> + if (USE_LINE_TS(payld) && TS_VALID(payld))
> + tde->last_ts = LINE_TSTAMP_GET(&payld->tsl);
> + else
> + tde->last_ts = 0;
> + }
> +}
> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index 59527193d6dd..6c6db95d0089 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h
...
> +#define SCMI_TLM_GET_UPDATE_INTERVAL_SECS(x) \
> + (le32_get_bits((x), GENMASK(20, 5)))
Why is this one little endian specific and the next just uses assumption of
CPU Endian?
> +#define SCMI_TLM_GET_UPDATE_INTERVAL_EXP(x) \
> + ({ \
> + int __signed_exp = FIELD_GET(GENMASK(4, 0), (x)); \
> + \
> + if (__signed_exp & BIT(4)) \
> + __signed_exp |= GENMASK(31, 5); \
sign_extend32() from bitops.h should work here and is much more self explanatory.
That would then make this something like
#define SCMI_TLM_GET_UPDATE_INTERVAL_EXP(x) \
sign_extend32(x, 4);
or you can mask it first if you like but I don't think it makes any difference
in practice.
> + __signed_exp; \
> + })
> +
> +#define SCMI_TLM_BUILD_UPDATE_INTERVAL(s, e) \
> + (FIELD_PREP(GENMASK(20, 5), (s)) | FIELD_PREP(GENMASK(4, 0), (e)))
> +
> +struct scmi_telemetry_update_report {
> + ktime_t timestamp;
> + unsigned int agent_id;
> + int status;
> + unsigned int num_dwords;
> + unsigned int dwords[];
More places where __counted_by is appropriate. I'll not comment on any others and
just assume you'll add them wherever appropriate.
> +};
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