ArmPkg/ArmScmiDxe: Fix the calculation of RequiredArraySize

As per the SCMI specification, section CLOCK_DESCRIBE_RATES mentions
that the value of num_rates_flags[11:0] in the response must be 3 if
the return format is the triplet. Due to the buggy firmware, this was
not noticed for long time. The firmware is now fixed resulting in
ClockDescribeRates() to fail with "Buffer Too Small" error as the
RequiredArraySize gets miscalculated as 72 instead of 24.

Fix the issue by reusing the logic for both the return format which
must work if num_rates_flags has correct value as expected from the
specification.

Cc: Girish Pathak <girish.pathak@arm.com>
Cc: Jeff Brasen <jbrasen@nvidia.com>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Tested-by: Pierre Gondois <pierre.gondois@arm.com>
Reported-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Tested-by: Sami Mujawar <sami.mujawar@arm.com>

1 files changed, 16 insertions, 23 deletions

diff --git a/ArmPkg/Drivers/ArmScmiDxe/ScmiClockProtocol.c b/ArmPkg/Drivers/ArmScmiDxe/ScmiClockProtocol.c
index 12a7e6df5d..f092208a66 100644
--- a/ArmPkg/Drivers/ArmScmiDxe/ScmiClockProtocol.c
+++ b/ArmPkg/Drivers/ArmScmiDxe/ScmiClockProtocol.c
@@ -236,12 +236,7 @@ ClockDescribeRates (
       *TotalRates = NUM_RATES (DescribeRates->NumRatesFlags)

                     + NUM_REMAIN_RATES (DescribeRates->NumRatesFlags);

 

-      if (*Format == ScmiClockRateFormatDiscrete) {

-        RequiredArraySize = (*TotalRates) * sizeof (UINT64);

-      } else {

-        // We need to return triplet of 64 bit value for each rate

-        RequiredArraySize = (*TotalRates) * 3 * sizeof (UINT64);

-      }

+      RequiredArraySize = (*TotalRates) * sizeof (UINT64);

 

       if (RequiredArraySize > (*RateArraySize)) {

         *RateArraySize = RequiredArraySize;

@@ -259,23 +254,21 @@ ClockDescribeRates (
           ConvertTo64Bit (Rate->Low, Rate->High);

       }

     } else {

-      for (RateNo = 0; RateNo < NUM_RATES (DescribeRates->NumRatesFlags); RateNo++) {

-        // Linear clock rates from minimum to maximum in steps

-        // Minimum clock rate.

-        Rate                                    = &DescribeRates->Rates[RateOffset++];

-        RateArray[RateIndex].ContinuousRate.Min =

-          ConvertTo64Bit (Rate->Low, Rate->High);

-

-        Rate = &DescribeRates->Rates[RateOffset++];

-        // Maximum clock rate.

-        RateArray[RateIndex].ContinuousRate.Max =

-          ConvertTo64Bit (Rate->Low, Rate->High);

-

-        Rate = &DescribeRates->Rates[RateOffset++];

-        // Step.

-        RateArray[RateIndex++].ContinuousRate.Step =

-          ConvertTo64Bit (Rate->Low, Rate->High);

-      }

+      // Linear clock rates from minimum to maximum in steps

+      // Minimum clock rate.

+      Rate                                    = &DescribeRates->Rates[RateOffset++];

+      RateArray[RateIndex].ContinuousRate.Min =

+        ConvertTo64Bit (Rate->Low, Rate->High);

+

+      Rate = &DescribeRates->Rates[RateOffset++];

+      // Maximum clock rate.

+      RateArray[RateIndex].ContinuousRate.Max =

+        ConvertTo64Bit (Rate->Low, Rate->High);

+

+      Rate = &DescribeRates->Rates[RateOffset++];

+      // Step.

+      RateArray[RateIndex++].ContinuousRate.Step =

+        ConvertTo64Bit (Rate->Low, Rate->High);

     }

   } while (NUM_REMAIN_RATES (DescribeRates->NumRatesFlags) != 0);