fix: unify fallthrough annotations

Compiling with -Wimplicit-fallthrough=3 (enabled by -Wextra) produces
many warnings about fallthrough comments either missing or being wrong.
Unify the comments so we comply with -Wextra.

Note that Coverity recommends against using the __attribute__ directive.
Also, zlib does not build with a higher value of -Wimplicit-fallthrough.
Finally, compilers strip comments before expanding macros. As such,
checkpatch's fallthrough annotation (or higher levels of the flag) isn't
really possible.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I060cf4f8dc04c02cbb45cf4ceb69569a8369ccee

drivers/imx/usdhc/imx_usdhc.c

@@ -136,7 +136,8 @@ static int imx_usdhc_send_cmd(struct mmc_cmd *cmd)
 		break;
 	case MMC_CMD(18):
 		multiple = 1;
-		/* fall thru for read op */
+		/* for read op */
+		/* fallthrough */
 	case MMC_CMD(17):
 	case MMC_CMD(8):
 		mixctl |= MIXCTRL_DTDSEL;
@@ -144,7 +145,8 @@ static int imx_usdhc_send_cmd(struct mmc_cmd *cmd)
 		break;
 	case MMC_CMD(25):
 		multiple = 1;
-		/* fall thru for data op flag */
+		/* for data op flag */
+		/* fallthrough */
 	case MMC_CMD(24):
 		data = 1;
 		break;

drivers/renesas/common/emmc/emmc_cmd.c

@@ -254,8 +254,7 @@ EMMC_ERROR_CODE emmc_exec_cmd(uint32_t error_mask, uint32_t *response)
 				(SD_INFO2_ALL_ERR | SD_INFO2_CLEAR));
 
 			state = ESTATE_ISSUE_CMD;
-			/* through */
-
+			/* fallthrough */
 		case ESTATE_ISSUE_CMD:
 			/* ARG */
 			SETR_32(SD_ARG, mmc_drv_obj.cmd_info.arg);
@@ -454,8 +453,8 @@ EMMC_ERROR_CODE emmc_exec_cmd(uint32_t error_mask, uint32_t *response)
 				SETR_32(SD_STOP, 0x00000000U);
 				mmc_drv_obj.during_dma_transfer = FALSE;
 			}
-			/* through */
 
+			/* fallthrough */
 		case ESTATE_ERROR:
 			if (err_not_care_flag == TRUE) {
 				mmc_drv_obj.during_cmd_processing = FALSE;

lib/libc/snprintf.c

@@ -209,6 +209,7 @@ loop:
 				break;
 			case 'X':
 				capitalise = true;
+				/* fallthrough */
 			case 'x':
 				unum = get_unum_va_args(args, l_count);
 				unsigned_num_print(&s, n, &chars_printed,

plat/mediatek/common/mtk_smc_handlers.c

@@ -51,6 +51,7 @@
 		x3 = x3 & MASK_32_BIT; \
 		x4 = x4 & MASK_32_BIT; \
 	} \
+	/* fallthrough */ \
 	case _smc_id##_AARCH64: \
 	{ \
 		if (_smc_id##_descriptor_index < 0) { \

plat/nxp/common/psci/plat_psci.c

@@ -350,7 +350,7 @@ static int _pwr_state_validate(uint32_t pwr_state,
 		else if (SOC_SYSTEM_STANDBY)
 			state->pwr_domain_state[PLAT_MAX_LVL] =
 				PLAT_MAX_RET_STATE;
-		 /* intentional fall-thru condition */
+		 /* fallthrough */
 	case PWR_STATE_LVL_SYS:
 		if (pwrdn && SOC_SYSTEM_PWR_DWN)
 			state->pwr_domain_state[PLAT_SYS_LVL] =
@@ -358,7 +358,7 @@ static int _pwr_state_validate(uint32_t pwr_state,
 		else if (SOC_SYSTEM_STANDBY)
 			state->pwr_domain_state[PLAT_SYS_LVL] =
 				PLAT_MAX_RET_STATE;
-		 /* intentional fall-thru condition */
+		 /* fallthrough */
 	case PWR_STATE_LVL_CLSTR:
 		if (pwrdn && SOC_CLUSTER_PWR_DWN)
 			state->pwr_domain_state[PLAT_CLSTR_LVL] =
@@ -366,7 +366,7 @@ static int _pwr_state_validate(uint32_t pwr_state,
 		else if (SOC_CLUSTER_STANDBY)
 			state->pwr_domain_state[PLAT_CLSTR_LVL] =
 				PLAT_MAX_RET_STATE;
-		 /* intentional fall-thru condition */
+		 /* fallthrough */
 	case PWR_STATE_LVL_CORE:
 		stat = PSCI_E_SUCCESS;
 

services/std_svc/spmd/spmd_main.c

@@ -868,7 +868,8 @@ uint64_t spmd_smc_handler(uint32_t smc_fid,
 						     FFA_ERROR_NOT_SUPPORTED);
 		}
 
-		/* Fall through to forward the call to the other world */
+		/* Forward the call to the other world */
+		/* fallthrough */
 	case FFA_MSG_SEND:
 	case FFA_MSG_SEND_DIRECT_RESP_SMC64:
 	case FFA_MEM_DONATE_SMC32:
@@ -908,7 +909,8 @@ uint64_t spmd_smc_handler(uint32_t smc_fid,
 			spmd_spm_core_sync_exit(0ULL);
 		}
 
-		/* Fall through to forward the call to the other world */
+		/* Forward the call to the other world */
+		/* fallthrough */
 	case FFA_INTERRUPT:
 	case FFA_MSG_YIELD:
 		/* This interface must be invoked only by the Secure world */