firmware: arm_scmi: Warn if domain frequency multiplier is 0 or rounded off

When (sustained_freq_khz * 1000) is less than sustained_perf_level, the
multiplier will be less than 1 and hence rounded down as 0. Similarly if
it is not multiple of sustained_perf_level the dom_info->mult_factor will
contain rounded down value and will end up impacting all the frequency
calculations done using it.

Add warning if and when the domain frequency multiplier is 0 or rounded
down so that it gives a clue to get the firmware tables fixed.

Suggested-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240119152338.3047620-1-sudeep.holla@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index 211e8e0aef2c2b4fade048990249c2444afb946a..9e7b1ee949408345c7484b28eb26db38ebd4cd18 100644 (file)
--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -270,15 +270,30 @@ scmi_perf_domain_attributes_get(const struct scmi_protocol_handle *ph,
                                        le32_to_cpu(attr->sustained_freq_khz);
                dom_info->sustained_perf_level =
                                        le32_to_cpu(attr->sustained_perf_level);
+               /*
+                * sustained_freq_khz = mult_factor * sustained_perf_level
+                * mult_factor must be non zero positive integer(not fraction)
+                */
                if (!dom_info->sustained_freq_khz ||
                    !dom_info->sustained_perf_level ||
-                   dom_info->level_indexing_mode)
+                   dom_info->level_indexing_mode) {
                        /* CPUFreq converts to kHz, hence default 1000 */
                        dom_info->mult_factor = 1000;
-               else
+               } else {
                        dom_info->mult_factor =
                                        (dom_info->sustained_freq_khz * 1000UL)
                                        / dom_info->sustained_perf_level;
+                       if ((dom_info->sustained_freq_khz * 1000UL) %
+                           dom_info->sustained_perf_level)
+                               dev_warn(ph->dev,
+                                        "multiplier for domain %d rounded\n",
+                                        dom_info->id);
+               }
+               if (!dom_info->mult_factor)
+                       dev_warn(ph->dev,
+                                "Wrong sustained perf/frequency(domain %d)\n",
+                                dom_info->id);
+
                strscpy(dom_info->info.name, attr->name,
                        SCMI_SHORT_NAME_MAX_SIZE);
        }