tty: serial: qcom-geni-serial: refactor qcom_geni_serial_send_chunk_fifo()

Shuffle the code a bit, drop unneeded variables, make types of others
more consistent and use uart_xmit_advance() instead of handling
tail->xmit manually.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20221229155030.418800-11-brgl@bgdev.plSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/qcom_geni_serial.c

@@ -93,7 +93,7 @@
 #define IO_MACRO_IO2_IO3_SWAP		0x4640
 
 /* We always configure 4 bytes per FIFO word */
-#define BYTES_PER_FIFO_WORD		4
+#define BYTES_PER_FIFO_WORD		4U
 
 struct qcom_geni_private_data {
 	/* NOTE: earlycon port will have NULL here */
@@ -704,36 +704,28 @@ static void qcom_geni_serial_start_rx(struct uart_port *uport)
 	writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
 }
 
-static int qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
-					    unsigned int chunk)
+static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
+					     unsigned int chunk)
 {
 	struct qcom_geni_serial_port *port = to_dev_port(uport);
 	struct circ_buf *xmit = &uport->state->xmit;
-	size_t remaining = chunk;
-	int i, tail = xmit->tail;
-
-	for (i = 0; i < chunk; ) {
-		unsigned int tx_bytes;
-		u8 buf[sizeof(u32)];
-		int c;
+	unsigned int tx_bytes, c, remaining = chunk;
+	u8 buf[BYTES_PER_FIFO_WORD];
 
+	while (remaining) {
 		memset(buf, 0, sizeof(buf));
-		tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);
+		tx_bytes = min(remaining, BYTES_PER_FIFO_WORD);
 
 		for (c = 0; c < tx_bytes ; c++) {
-			buf[c] = xmit->buf[tail++];
-			tail &= UART_XMIT_SIZE - 1;
+			buf[c] = xmit->buf[xmit->tail];
+			uart_xmit_advance(uport, 1);
 		}
 
 		iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);
 
-		i += tx_bytes;
-		uport->icount.tx += tx_bytes;
 		remaining -= tx_bytes;
 		port->tx_remaining -= tx_bytes;
 	}
-
-	return tail;
 }
 
 static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
@@ -778,7 +770,7 @@ static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
 					uport->membase + SE_GENI_M_IRQ_EN);
 	}
 
-	xmit->tail = qcom_geni_serial_send_chunk_fifo(uport, chunk);
+	qcom_geni_serial_send_chunk_fifo(uport, chunk);
 
 	/*
 	 * The tx fifo watermark is level triggered and latched. Though we had