linux-kernel - [PATCH v1 2/3] soc: mediatek: mtk-cmdq: Mark very unlikely branches as such

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Message-ID: <20240918100620.103536-3-angelogioacchino.delregno@collabora.com>
Date: Wed, 18 Sep 2024 12:06:19 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: linux-mediatek@...ts.infradead.org
Cc: matthias.bgg@...il.com,
	angelogioacchino.delregno@...labora.com,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kernel@...labora.com
Subject: [PATCH v1 2/3] soc: mediatek: mtk-cmdq: Mark very unlikely branches as such

Calling cmdq packet builders with an unsupported event number,
or without left/right operands (in the case of logic commands)
means that the caller (another driver) wants to perform an
unsupported operation, so this means that the caller must be
fixed instead.

Anyway, such checks are here for safety and, unless any driver
bug or any kind of misconfiguration is present, will always be
false so add a very unlikely hint for those.

Knowing that CPUs' branch predictors (and compilers, anyway) are
indeed smart about these cases, this is done mainly for human
readability purposes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/soc/mediatek/mtk-cmdq-helper.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
index 620c371fd1fc..4ffd1a35df87 100644
--- a/drivers/soc/mediatek/mtk-cmdq-helper.c
+++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
@@ -336,7 +336,7 @@ int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event, bool clear)
 	struct cmdq_instruction inst = { {0} };
 	u32 clear_option = clear ? CMDQ_WFE_UPDATE : 0;
 
-	if (event >= CMDQ_MAX_EVENT)
+	if (unlikely(event >= CMDQ_MAX_EVENT))
 		return -EINVAL;
 
 	inst.op = CMDQ_CODE_WFE;
@@ -351,7 +351,7 @@ int cmdq_pkt_acquire_event(struct cmdq_pkt *pkt, u16 event)
 {
 	struct cmdq_instruction inst = {};
 
-	if (event >= CMDQ_MAX_EVENT)
+	if (unlikely(event >= CMDQ_MAX_EVENT))
 		return -EINVAL;
 
 	inst.op = CMDQ_CODE_WFE;
@@ -366,7 +366,7 @@ int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u16 event)
 {
 	struct cmdq_instruction inst = { {0} };
 
-	if (event >= CMDQ_MAX_EVENT)
+	if (unlikely(event >= CMDQ_MAX_EVENT))
 		return -EINVAL;
 
 	inst.op = CMDQ_CODE_WFE;
@@ -381,7 +381,7 @@ int cmdq_pkt_set_event(struct cmdq_pkt *pkt, u16 event)
 {
 	struct cmdq_instruction inst = {};
 
-	if (event >= CMDQ_MAX_EVENT)
+	if (unlikely(event >= CMDQ_MAX_EVENT))
 		return -EINVAL;
 
 	inst.op = CMDQ_CODE_WFE;
@@ -476,7 +476,7 @@ int cmdq_pkt_logic_command(struct cmdq_pkt *pkt, u16 result_reg_idx,
 {
 	struct cmdq_instruction inst = { {0} };
 
-	if (!left_operand || !right_operand || s_op >= CMDQ_LOGIC_MAX)
+	if (unlikely(!left_operand || !right_operand || s_op >= CMDQ_LOGIC_MAX))
 		return -EINVAL;
 
 	inst.op = CMDQ_CODE_LOGIC;
-- 
2.46.0