[PATCH v2] firmware: arm_scmi: Warn if domain frequency multiplier is 0 or rounded off

[Sudeep Holla]

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 at arm.com>
Reviewed-by: Pierre Gondois <pierre.gondois at arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi at arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
---
 drivers/firmware/arm_scmi/perf.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

v1->v2:
	- Added comment regarding the requirements on sustained_freq_khz
	  and sustained_perf_level obtained from the SCMI firmware
	- Changed pr_warn to dev_warn

diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index 8ea2a7b3d35d..9fe123e1f3c7 100644
--- 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);
 	}
-- 
2.43.0