mailbox: pcc: Refactor and simplify check_and_ack()

The existing check_and_ack() function had unnecessary complexity. The
logic could be streamlined to improve code readability and maintainability.

The command update register needs to be updated in order to acknowledge
the platform notification through type 4 channel. So it can be done
unconditionally. Currently it is complicated just to make use of
pcc_send_data() which also executes the same updation.

In order to simplify, let us just ring the doorbell directly from
check_and_ack() instead of calling into pcc_send_data(). While at it,
rename it into pcc_chan_check_and_ack() to maintain consistency in the
driver.

Acked-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Adam Young <admiyo@os.amperecomputing.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: sudeep-holla

drivers/mailbox/pcc.c

@@ -117,8 +117,6 @@ struct pcc_chan_info {
 static struct pcc_chan_info *chan_info;
 static int pcc_chan_count;
 
-static int pcc_send_data(struct mbox_chan *chan, void *data);
-
 /*
  * PCC can be used with perf critical drivers such as CPPC
  * So it makes sense to locally cache the virtual address and
@@ -288,33 +286,24 @@ static int pcc_mbox_error_check_and_clear(struct pcc_chan_info *pchan)
 	return 0;
 }
 
-static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
+static void pcc_chan_acknowledge(struct pcc_chan_info *pchan)
 {
-	struct acpi_pcct_ext_pcc_shared_memory pcc_hdr;
+	struct acpi_pcct_ext_pcc_shared_memory __iomem *pcc_hdr;
 
 	if (pchan->type != ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
 		return;
-	/* If the memory region has not been mapped, we cannot
-	 * determine if we need to send the message, but we still
-	 * need to set the cmd_update flag before returning.
-	 */
-	if (pchan->chan.shmem == NULL) {
-		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
-		return;
-	}
-	memcpy_fromio(&pcc_hdr, pchan->chan.shmem,
-		      sizeof(struct acpi_pcct_ext_pcc_shared_memory));
+
+	pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+
+	pcc_hdr = pchan->chan.shmem;
+
 	/*
-	 * The PCC slave subspace channel needs to set the command complete bit
-	 * after processing message. If the PCC_ACK_FLAG is set, it should also
-	 * ring the doorbell.
-	 *
-	 * The PCC master subspace channel clears chan_in_use to free channel.
+	 * The PCC slave subspace channel needs to set the command
+	 * complete bit after processing message. If the PCC_ACK_FLAG
+	 * is set, it should also ring the doorbell.
 	 */
-	if (pcc_hdr.flags & PCC_CMD_COMPLETION_NOTIFY)
-		pcc_send_data(chan, NULL);
-	else
-		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+	if (ioread32(&pcc_hdr->flags) & PCC_CMD_COMPLETION_NOTIFY)
+		pcc_chan_reg_read_modify_write(&pchan->db);
 }
 
 /**
@@ -353,7 +342,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	pchan->chan_in_use = false;
 	mbox_chan_received_data(chan, NULL);
 
-	check_and_ack(pchan, chan);
+	pcc_chan_acknowledge(pchan);
 
 	return IRQ_HANDLED;
 }