firmware: arm_scmi: Add clock determine_rate operation

Add a clock operation to help determining the effective rate, closest to
the required one, that a specific clock can support.

Calculation is currently performed kernel side and the logic is taken
directly from the SCMI Clock driver: embedding the determinate rate logic
in the protocol layer enables simplifications in the SCMI Clock protocol
interface and will more easily accommodate further evolutions where such
determine_rate logic into is optionally delegated to the platform SCMI
server.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260508153300.2224715-3-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
index ab36871650a1ff890c4cb7f67d3ded2622a72868..54b55517b7591c87a0da2176d7ed07d2652b0bd8 100644 (file)
--- a/drivers/firmware/arm_scmi/clock.c
+++ b/drivers/firmware/arm_scmi/clock.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2018-2022 ARM Ltd.
  */
 
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/limits.h>
 #include <linux/sort.h>
@@ -624,6 +625,46 @@ static int scmi_clock_rate_set(const struct scmi_protocol_handle *ph,
        return ret;
 }
 
+static int scmi_clock_determine_rate(const struct scmi_protocol_handle *ph,
+                                    u32 clk_id, unsigned long *rate)
+{
+       u64 fmin, fmax, ftmp;
+       struct scmi_clock_info *clk;
+       struct clock_info *ci = ph->get_priv(ph);
+
+       if (!rate)
+               return -EINVAL;
+
+       clk = scmi_clock_domain_lookup(ci, clk_id);
+       if (IS_ERR(clk))
+               return PTR_ERR(clk);
+
+       /*
+        * If we can't figure out what rate it will be, so just return the
+        * rate back to the caller.
+        */
+       if (clk->rate_discrete)
+               return 0;
+
+       fmin = clk->range.min_rate;
+       fmax = clk->range.max_rate;
+       if (*rate <= fmin) {
+               *rate = fmin;
+               return 0;
+       } else if (*rate >= fmax) {
+               *rate = fmax;
+               return 0;
+       }
+
+       ftmp = *rate - fmin;
+       ftmp += clk->range.step_size - 1; /* to round up */
+       ftmp = div64_ul(ftmp, clk->range.step_size);
+
+       *rate = ftmp * clk->range.step_size + fmin;
+
+       return 0;
+}
+
 static int
 scmi_clock_config_set(const struct scmi_protocol_handle *ph, u32 clk_id,
                      enum clk_state state,
@@ -936,6 +977,7 @@ static const struct scmi_clk_proto_ops clk_proto_ops = {
        .info_get = scmi_clock_info_get,
        .rate_get = scmi_clock_rate_get,
        .rate_set = scmi_clock_rate_set,
+       .determine_rate = scmi_clock_determine_rate,
        .enable = scmi_clock_enable,
        .disable = scmi_clock_disable,
        .state_get = scmi_clock_state_get,

diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 8d0b106caed8a1a33fb74f03465ce77ec427da47..984117f51695d31a1c3f257f3397a87d34171d9b 100644 (file)
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -91,6 +91,10 @@ enum scmi_clock_oem_config {
  * @info_get: get the information of the specified clock
  * @rate_get: request the current clock rate of a clock
  * @rate_set: set the clock rate of a clock
+ * @determine_rate: determine the effective rate that can be supported by a
+ *                 clock calculating the closest allowed rate.
+ *                 Note that @rate is an input/output parameter used both to
+ *                 describe the requested rate and report the closest match
  * @enable: enables the specified clock
  * @disable: disables the specified clock
  * @state_get: get the status of the specified clock
@@ -108,6 +112,8 @@ struct scmi_clk_proto_ops {
                        u64 *rate);
        int (*rate_set)(const struct scmi_protocol_handle *ph, u32 clk_id,
                        u64 rate);
+       int (*determine_rate)(const struct scmi_protocol_handle *ph, u32 clk_id,
+                             unsigned long *rate);
        int (*enable)(const struct scmi_protocol_handle *ph, u32 clk_id,
                      bool atomic);
        int (*disable)(const struct scmi_protocol_handle *ph, u32 clk_id,