[PATCH 10/11] firmware: arm_scmi: Use bound iterators to minimize discovered rates
From: Cristian Marussi <cristian.marussi@arm.com>
Date: 2026-02-27 15:34:11
Also in:
arm-scmi, linux-clk, linux-renesas-soc, lkml
Subsystem:
system control & power/management interface (scpi/scmi) message protocol drivers, the rest · Maintainers:
Sudeep Holla, Linus Torvalds
Clock rates are guaranteed to be returned in ascending order for SCMI clock protocol versions greater than 1.0: in such a case, use bounded iterators to minimize the number of message exchanges needed to discover min and max rate. Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- drivers/firmware/arm_scmi/clock.c | 92 +++++++++++++++++++++++++++---- 1 file changed, 82 insertions(+), 10 deletions(-)
diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
index d7df5c45836e..a0de10652abe 100644
--- a/drivers/firmware/arm_scmi/clock.c
+++ b/drivers/firmware/arm_scmi/clock.c@@ -160,6 +160,7 @@ struct scmi_clock_rate_notify_payld { struct scmi_clock_desc { u32 id; bool rate_discrete; + unsigned int tot_rates; unsigned int num_rates; u64 *rates; #define RATE_MIN 0
@@ -483,15 +484,16 @@ iter_clk_describe_update_state(struct scmi_iterator_state *st, } if (!st->max_resources) { - int num_rates = st->num_returned + st->num_remaining; + unsigned int tot_rates = st->num_returned + st->num_remaining; - p->clkd->rates = devm_kcalloc(p->dev, num_rates, + p->clkd->rates = devm_kcalloc(p->dev, tot_rates, sizeof(*p->clkd->rates), GFP_KERNEL); if (!p->clkd->rates) return -ENOMEM; /* max_resources is used by the iterators to control bounds */ - st->max_resources = st->num_returned + st->num_remaining; + p->clkd->tot_rates = tot_rates; + st->max_resources = tot_rates; } return 0;
@@ -514,8 +516,8 @@ iter_clk_describe_process_response(const struct scmi_protocol_handle *ph, } static int -scmi_clock_describe_rates_get(const struct scmi_protocol_handle *ph, u32 clk_id, - struct clock_info *cinfo) +scmi_clock_describe_rates_get_full(const struct scmi_protocol_handle *ph, + struct scmi_clock_desc *clkd) { int ret; void *iter;
@@ -524,7 +526,6 @@ scmi_clock_describe_rates_get(const struct scmi_protocol_handle *ph, u32 clk_id, .update_state = iter_clk_describe_update_state, .process_response = iter_clk_describe_process_response, }; - struct scmi_clock_desc *clkd = &cinfo->clkds[clk_id]; struct scmi_clk_ipriv cpriv = { .clkd = clkd, .dev = ph->dev,
@@ -544,19 +545,90 @@ scmi_clock_describe_rates_get(const struct scmi_protocol_handle *ph, u32 clk_id, if (!clkd->num_rates) return 0; + if (clkd->rate_discrete) + sort(clkd->rates, clkd->num_rates, + sizeof(clkd->rates[0]), rate_cmp_func, NULL); + + return 0; +} + +static int +scmi_clock_describe_rates_get_lazy(const struct scmi_protocol_handle *ph, + struct scmi_clock_desc *clkd) +{ + struct scmi_iterator_ops ops = { + .prepare_message = iter_clk_describe_prepare_message, + .update_state = iter_clk_describe_update_state, + .process_response = iter_clk_describe_process_response, + }; + struct scmi_clk_ipriv cpriv = { + .clkd = clkd, + .dev = ph->dev, + }; + unsigned int first, last; + void *iter; + int ret; + + iter = ph->hops->iter_response_init(ph, &ops, 0, CLOCK_DESCRIBE_RATES, + sizeof(struct scmi_msg_clock_describe_rates), + &cpriv); + if (IS_ERR(iter)) + return PTR_ERR(iter); + + /* Try to grab a triplet, so that in case is NON-discrete we are done */ + first = 0; + last = 2; + ret = ph->hops->iter_response_run_bound(iter, &first, &last); + if (ret) + goto out; + + /* If discrete grab the last value, which should be the max */ + if (clkd->rate_discrete && clkd->tot_rates > 3) { + first = clkd->tot_rates - 1; + last = clkd->tot_rates - 1; + ret = ph->hops->iter_response_run_bound(iter, &first, &last); + } + +out: + ph->hops->iter_response_cleanup(iter); + + return ret; +} + +static int +scmi_clock_describe_rates_get(const struct scmi_protocol_handle *ph, + u32 clk_id, struct clock_info *cinfo) +{ + struct scmi_clock_desc *clkd = &cinfo->clkds[clk_id]; + int ret; + + /* + * Since only after SCMI Clock v1.0 the returned rates are guaranteed to + * be discovered in ascending order, lazy enumeration cannot be use for + * SCMI Clock v1.0 protocol. + */ + if (PROTOCOL_REV_MAJOR(ph->version) > 0x1) + ret = scmi_clock_describe_rates_get_lazy(ph, clkd); + else + ret = scmi_clock_describe_rates_get_full(ph, clkd); + + if (ret) + return ret; + + clkd->info.min_rate = clkd->rates[RATE_MIN]; if (!clkd->rate_discrete) { clkd->info.max_rate = clkd->rates[RATE_MAX]; dev_dbg(ph->dev, "Min %llu Max %llu Step %llu Hz\n", clkd->rates[RATE_MIN], clkd->rates[RATE_MAX], clkd->rates[RATE_STEP]); } else { - sort(clkd->rates, clkd->num_rates, - sizeof(clkd->rates[0]), rate_cmp_func, NULL); clkd->info.max_rate = clkd->rates[clkd->num_rates - 1]; + dev_dbg(ph->dev, "Clock:%s DISCRETE:%d -> Min %llu Max %llu\n", + clkd->info.name, clkd->rate_discrete, + clkd->info.min_rate, clkd->info.max_rate); } - clkd->info.min_rate = clkd->rates[RATE_MIN]; - return 0; + return ret; } static int
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2.53.0