firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero

Firmware can provide zero as values for sustained performance level and
corresponding sustained frequency in kHz in order to hide the actual
frequencies and provide only abstract values. It may endup with divide
by zero scenario resulting in kernel panic.

Let's set the multiplication factor to one if either one or both of them
(sustained_perf_level and sustained_freq) are set to zero.

Fixes: a9e3fbfaa0ff ("firmware: arm_scmi: add initial support for performance protocol")
Reported-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index 721e6c57beae5bfecb0f135c514fedd9ea2bdff0..64342944d9175c54918100c36f0b43a20e6acae3 100644 (file)
--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -166,7 +166,13 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain,
                                        le32_to_cpu(attr->sustained_freq_khz);
                dom_info->sustained_perf_level =
                                        le32_to_cpu(attr->sustained_perf_level);
-               dom_info->mult_factor = (dom_info->sustained_freq_khz * 1000) /
+               if (!dom_info->sustained_freq_khz ||
+                   !dom_info->sustained_perf_level)
+                       /* CPUFreq converts to kHz, hence default 1000 */
+                       dom_info->mult_factor = 1000;
+               else
+                       dom_info->mult_factor =
+                                       (dom_info->sustained_freq_khz * 1000) /
                                        dom_info->sustained_perf_level;
                memcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE);
        }