irqchip/gic-v3-its: Refactor command encoding

The way we encode the various ITS command fields is both tedious
and error prone. Let's introduce a helper function that performs
the encoding, and convert the existing encoders to use that
helper. It also has the advantage of expressing the encoding in
a way that matches the architecture specification.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic-v3-its.c

@@ -193,58 +193,56 @@ struct its_cmd_block {
 typedef struct its_collection *(*its_cmd_builder_t)(struct its_cmd_block *,
 						    struct its_cmd_desc *);
 
+static void its_mask_encode(u64 *raw_cmd, u64 val, int h, int l)
+{
+	u64 mask = GENMASK_ULL(h, l);
+	*raw_cmd &= ~mask;
+	*raw_cmd |= (val << l) & mask;
+}
+
 static void its_encode_cmd(struct its_cmd_block *cmd, u8 cmd_nr)
 {
-	cmd->raw_cmd[0] &= ~0xffULL;
-	cmd->raw_cmd[0] |= cmd_nr;
+	its_mask_encode(&cmd->raw_cmd[0], cmd_nr, 7, 0);
 }
 
 static void its_encode_devid(struct its_cmd_block *cmd, u32 devid)
 {
-	cmd->raw_cmd[0] &= BIT_ULL(32) - 1;
-	cmd->raw_cmd[0] |= ((u64)devid) << 32;
+	its_mask_encode(&cmd->raw_cmd[0], devid, 63, 32);
 }
 
 static void its_encode_event_id(struct its_cmd_block *cmd, u32 id)
 {
-	cmd->raw_cmd[1] &= ~0xffffffffULL;
-	cmd->raw_cmd[1] |= id;
+	its_mask_encode(&cmd->raw_cmd[1], id, 31, 0);
 }
 
 static void its_encode_phys_id(struct its_cmd_block *cmd, u32 phys_id)
 {
-	cmd->raw_cmd[1] &= 0xffffffffULL;
-	cmd->raw_cmd[1] |= ((u64)phys_id) << 32;
+	its_mask_encode(&cmd->raw_cmd[1], phys_id, 63, 32);
 }
 
 static void its_encode_size(struct its_cmd_block *cmd, u8 size)
 {
-	cmd->raw_cmd[1] &= ~0x1fULL;
-	cmd->raw_cmd[1] |= size & 0x1f;
+	its_mask_encode(&cmd->raw_cmd[1], size, 4, 0);
 }
 
 static void its_encode_itt(struct its_cmd_block *cmd, u64 itt_addr)
 {
-	cmd->raw_cmd[2] &= ~0xffffffffffffULL;
-	cmd->raw_cmd[2] |= itt_addr & 0xffffffffff00ULL;
+	its_mask_encode(&cmd->raw_cmd[2], itt_addr >> 8, 50, 8);
 }
 
 static void its_encode_valid(struct its_cmd_block *cmd, int valid)
 {
-	cmd->raw_cmd[2] &= ~(1ULL << 63);
-	cmd->raw_cmd[2] |= ((u64)!!valid) << 63;
+	its_mask_encode(&cmd->raw_cmd[2], !!valid, 63, 63);
 }
 
 static void its_encode_target(struct its_cmd_block *cmd, u64 target_addr)
 {
-	cmd->raw_cmd[2] &= ~(0xffffffffULL << 16);
-	cmd->raw_cmd[2] |= (target_addr & (0xffffffffULL << 16));
+	its_mask_encode(&cmd->raw_cmd[2], target_addr >> 16, 50, 16);
 }
 
 static void its_encode_collection(struct its_cmd_block *cmd, u16 col)
 {
-	cmd->raw_cmd[2] &= ~0xffffULL;
-	cmd->raw_cmd[2] |= col;
+	its_mask_encode(&cmd->raw_cmd[2], col, 15, 0);
 }
 
 static inline void its_fixup_cmd(struct its_cmd_block *cmd)