soc: mediatek: mtk-cmdq: Add cmdq_pkt_acquire_event() function

Add cmdq_pkt_acquire_event() function to support CMDQ user making
an instruction for acquiring event.

CMDQ users can use cmdq_pkt_acquire_event() as `mutex_lock`
and cmdq_pkt_clear_event() as `mutex_unlock` to protect the global
resource modified instructions between them.

cmdq_pkt_acquire_event() would wait for event to be cleared.
After event is cleared by cmdq_pkt_clear_event() in other GCE threads,
cmdq_pkt_acquire_event() would set event and keep executing next
instruction. So the mutex would work like this:

    cmdq_pkt_acquire_event() /* mutex lock */

    /* critical secton instructions that modified global resource */

    cmdq_pkt_clear_event() /* mutex unlock */

Prevent the critical section instructions from being affected by other
GCE threads.
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240307013458.23550-5-jason-jh.lin@mediatek.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

drivers/soc/mediatek/mtk-cmdq-helper.c

@@ -334,6 +334,21 @@ int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event, bool clear)
 }
 EXPORT_SYMBOL(cmdq_pkt_wfe);
 
+int cmdq_pkt_acquire_event(struct cmdq_pkt *pkt, u16 event)
+{
+	struct cmdq_instruction inst = {};
+
+	if (event >= CMDQ_MAX_EVENT)
+		return -EINVAL;
+
+	inst.op = CMDQ_CODE_WFE;
+	inst.value = CMDQ_WFE_UPDATE | CMDQ_WFE_UPDATE_VALUE | CMDQ_WFE_WAIT;
+	inst.event = event;
+
+	return cmdq_pkt_append_command(pkt, inst);
+}
+EXPORT_SYMBOL(cmdq_pkt_acquire_event);
+
 int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u16 event)
 {
 	struct cmdq_instruction inst = { {0} };

include/linux/soc/mediatek/mtk-cmdq.h

@@ -206,6 +206,21 @@ int cmdq_pkt_mem_move(struct cmdq_pkt *pkt, dma_addr_t src_addr, dma_addr_t dst_
  */
 int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event, bool clear);
 
+/**
+ * cmdq_pkt_acquire_event() - append acquire event command to the CMDQ packet
+ * @pkt:	the CMDQ packet
+ * @event:	the desired event to be acquired
+ *
+ * User can use cmdq_pkt_acquire_event() as `mutex_lock` and cmdq_pkt_clear_event()
+ * as `mutex_unlock` to protect some `critical section` instructions between them.
+ * cmdq_pkt_acquire_event() would wait for event to be cleared.
+ * After event is cleared by cmdq_pkt_clear_event in other GCE threads,
+ * cmdq_pkt_acquire_event() would set event and keep executing next instruction.
+ *
+ * Return: 0 for success; else the error code is returned
+ */
+int cmdq_pkt_acquire_event(struct cmdq_pkt *pkt, u16 event);
+
 /**
  * cmdq_pkt_clear_event() - append clear event command to the CMDQ packet
  * @pkt:	the CMDQ packet