src: Make implicit fall throughs explicit

Implicit fall throughs are a perpetual source of bugs and Coverity Scan
issues, so let's squash them once and for all. GCC can flag implicit fall
throughs using the -Wimplicit-fallthrough warning, and this should
ensure no more enter the code base. However, many fall throughs are
intentional, and we can use the following comment style to have GCC
suppress the warning.

    switch (x) {
    case 1:
            y += 1;
	    /* fall through */
    case 2:
            y += 2;
	    /* fall through - but this time with an explanation */
    default:
            y += 3;
    }

This patch adds comments for all remaining intentional fall throughs,
and tweaks some existing fall through comments to fit the syntax that
GCC expects.

Change-Id: I1d75637a434a955a58d166ad203e49620d7395ed
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34297
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

5 files changed, 22 insertions, 25 deletions

diff --git a/src/vendorcode/amd/agesa/f16kb/Proc/CPU/Family/0x16/KB/F16KbUtilities.c b/src/vendorcode/amd/agesa/f16kb/Proc/CPU/Family/0x16/KB/F16KbUtilities.c
index ed94e79f78..ccc7343d1b 100644
--- a/src/vendorcode/amd/agesa/f16kb/Proc/CPU/Family/0x16/KB/F16KbUtilities.c
+++ b/src/vendorcode/amd/agesa/f16kb/Proc/CPU/Family/0x16/KB/F16KbUtilities.c
@@ -242,9 +242,11 @@ F16KbSetDownCoreRegister (
   case CORE_LEVEL_COMPUTE_UNIT_THREE:
     TempVar32_a = TempVar32_a << 1;
     CoresPerComputeUnit++;
+    // fall through
   case CORE_LEVEL_COMPUTE_UNIT_TWO:
     TempVar32_a = TempVar32_a << 1;
     CoresPerComputeUnit++;
+    // fall through
   case CORE_LEVEL_COMPUTE_UNIT:
     TempVar32_a = (TempVar32_a << 1) - 1;
     TempVar32_a = FOUR_CORE_COMPUTE_UNIT_BITMAP & (~TempVar32_a);
diff --git a/src/vendorcode/amd/agesa/f16kb/Proc/CPU/S3.c b/src/vendorcode/amd/agesa/f16kb/Proc/CPU/S3.c
index 4b6128e245..42aebb67d1 100644
--- a/src/vendorcode/amd/agesa/f16kb/Proc/CPU/S3.c
+++ b/src/vendorcode/amd/agesa/f16kb/Proc/CPU/S3.c
@@ -224,25 +224,25 @@ SaveDeviceContext (
     switch (Device.CommonDeviceHeader->Type) {
     case DEV_TYPE_PCI_PRE_ESR:
       SavePciDevice (StdHeader, Device.PciDevice, CallPoint, &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_PCI:
       Device.PciDevice++;
       break;
     case DEV_TYPE_CPCI_PRE_ESR:
       SaveConditionalPciDevice (StdHeader, Device.CPciDevice, CallPoint, &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_CPCI:
       Device.CPciDevice++;
       break;
     case DEV_TYPE_MSR_PRE_ESR:
       SaveMsrDevice (StdHeader, Device.MsrDevice, CallPoint, (UINT64 **) &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_MSR:
       Device.MsrDevice++;
       break;
     case DEV_TYPE_CMSR_PRE_ESR:
       SaveConditionalMsrDevice (StdHeader, Device.CMsrDevice, CallPoint, (UINT64 **) &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_CMSR:
       Device.CMsrDevice++;
       break;
@@ -255,25 +255,25 @@ SaveDeviceContext (
     switch (Device.CommonDeviceHeader->Type) {
     case DEV_TYPE_PCI:
       SavePciDevice (StdHeader, Device.PciDevice, CallPoint, &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_PCI_PRE_ESR:
       Device.PciDevice++;
       break;
     case DEV_TYPE_CPCI:
       SaveConditionalPciDevice (StdHeader, Device.CPciDevice, CallPoint, &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_CPCI_PRE_ESR:
       Device.CPciDevice++;
       break;
     case DEV_TYPE_MSR:
       SaveMsrDevice (StdHeader, Device.MsrDevice, CallPoint, (UINT64 **) &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_MSR_PRE_ESR:
       Device.MsrDevice++;
       break;
     case DEV_TYPE_CMSR:
       SaveConditionalMsrDevice (StdHeader, Device.CMsrDevice, CallPoint, (UINT64 **) &OrMask);
-      // Fall through to advance the pointer after saving context
+      // fall through - advance the pointer after saving context
     case DEV_TYPE_CMSR_PRE_ESR:
       Device.CMsrDevice++;
       break;
@@ -678,25 +678,25 @@ RestorePreESRContext (
     switch (Device.CommonDeviceHeader->Type) {
     case DEV_TYPE_PCI_PRE_ESR:
       RestorePciDevice (StdHeader, Device.PciDevice, CallPoint, OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_PCI:
       Device.PciDevice++;
       break;
     case DEV_TYPE_CPCI_PRE_ESR:
       RestoreConditionalPciDevice (StdHeader, Device.CPciDevice, CallPoint, OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_CPCI:
       Device.CPciDevice++;
       break;
     case DEV_TYPE_MSR_PRE_ESR:
       RestoreMsrDevice (StdHeader, Device.MsrDevice, CallPoint, (UINT64 **) OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_MSR:
       Device.MsrDevice++;
       break;
     case DEV_TYPE_CMSR_PRE_ESR:
       RestoreConditionalMsrDevice (StdHeader, Device.CMsrDevice, CallPoint, (UINT64 **) OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_CMSR:
       Device.CMsrDevice++;
       break;
@@ -738,25 +738,25 @@ RestorePostESRContext (
     switch (Device.CommonDeviceHeader->Type) {
     case DEV_TYPE_PCI:
       RestorePciDevice (StdHeader, Device.PciDevice, CallPoint, &OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_PCI_PRE_ESR:
       Device.PciDevice++;
       break;
     case DEV_TYPE_CPCI:
       RestoreConditionalPciDevice (StdHeader, Device.CPciDevice, CallPoint, &OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_CPCI_PRE_ESR:
       Device.CPciDevice++;
       break;
     case DEV_TYPE_MSR:
       RestoreMsrDevice (StdHeader, Device.MsrDevice, CallPoint, (UINT64 **) &OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_MSR_PRE_ESR:
       Device.MsrDevice++;
       break;
     case DEV_TYPE_CMSR:
       RestoreConditionalMsrDevice (StdHeader, Device.CMsrDevice, CallPoint, (UINT64 **) &OrMaskPtr);
-      // Fall through to advance the pointer after restoring context
+      // fall through - advance the pointer after restoring context
     case DEV_TYPE_CMSR_PRE_ESR:
       Device.CMsrDevice++;
       break;
diff --git a/src/vendorcode/amd/agesa/f16kb/Proc/IDS/Debug/IdsDebugPrint.c b/src/vendorcode/amd/agesa/f16kb/Proc/IDS/Debug/IdsDebugPrint.c
index 4163d828de..c3e4ade14b 100644
--- a/src/vendorcode/amd/agesa/f16kb/Proc/IDS/Debug/IdsDebugPrint.c
+++ b/src/vendorcode/amd/agesa/f16kb/Proc/IDS/Debug/IdsDebugPrint.c
@@ -375,9 +375,7 @@ AmdIdsDebugPrintWorker (
       case 'X':
         Flags |= PREFIX_ZERO;
         Width = sizeof (UINT64) * 2;
-        //
-        // break skipped on purpose
-        //
+	// fall through
       case 'x':
         if ((Flags & LONG_TYPE) == LONG_TYPE) {
           Value = VA_ARG (Marker, UINT64);
diff --git a/src/vendorcode/amd/agesa/f16kb/Proc/Mem/Main/muc.c b/src/vendorcode/amd/agesa/f16kb/Proc/Mem/Main/muc.c
index 8d8177325e..980cd33666 100644
--- a/src/vendorcode/amd/agesa/f16kb/Proc/Mem/Main/muc.c
+++ b/src/vendorcode/amd/agesa/f16kb/Proc/Mem/Main/muc.c
@@ -211,8 +211,7 @@ MemUFillTrainPattern (
       break;
     case TestPatternJD256B:
       k >>= 1;
-      // break is not being used here because TestPatternJD256B also need
-      // to run TestPatternJD256A sequence.
+      // fall through - TestPatternJD256B also need to run TestPatternJD256A sequence
     case TestPatternJD256A:
       k >>= 3;
       ASSERT (k < sizeof (PatternJD_256));
@@ -220,8 +219,7 @@ MemUFillTrainPattern (
       break;
     case TestPatternJD1B:
       k >>= 1;
-      // break is not being used here because TestPatternJD1B also need
-      // to run TestPatternJD1A sequence.
+      // fall through - TestPatternJD1B also need to run TestPatternJD1A sequence
     case TestPatternJD1A:
       k >>= 3;
       i = (UINT8) (k >> 3);
diff --git a/src/vendorcode/amd/agesa/f16kb/Proc/Mem/NB/mnphy.c b/src/vendorcode/amd/agesa/f16kb/Proc/Mem/NB/mnphy.c
index 356d4e3918..c20d5a2fd0 100644
--- a/src/vendorcode/amd/agesa/f16kb/Proc/Mem/NB/mnphy.c
+++ b/src/vendorcode/amd/agesa/f16kb/Proc/Mem/NB/mnphy.c
@@ -487,8 +487,7 @@ MemNcmnGetSetTrainDlyUnb (
     } else if (Rank) {
       Index += 0x60;
     }
-    // break is not being used here because AccessRdDqsDly and AccessWrDatDly also need
-    // to run AccessPhRecDly sequence.
+    // fall through - AccessRdDqsDly and AccessWrDatDly also need to run AccessPhRecDly sequence
   case AccessPhRecDly:
     Index += (Byte / 4);
     Offset = 8 * (Byte % 4);