serial: 8250_mtk: Make sure to select the right FEATURE_SEL

Set the FEATURE_SEL at probe time to make sure that BIT(0) is enabled:
this guarantees that when the port is configured as AP UART, the
right register layout is interpreted by the UART IP.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220427132328.228297-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index cd62a5f..28e3645 100644 (file)
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -54,6 +54,9 @@
 #define MTK_UART_TX_TRIGGER    1
 #define MTK_UART_RX_TRIGGER    MTK_UART_RX_SIZE
 
+#define MTK_UART_FEATURE_SEL   39      /* Feature Selection register */
+#define MTK_UART_FEAT_NEWRMAP  BIT(0)  /* Use new register map */
+
 #ifdef CONFIG_SERIAL_8250_DMA
 enum dma_rx_status {
        DMA_RX_START = 0,
@@ -569,6 +572,10 @@ static int mtk8250_probe(struct platform_device *pdev)
                uart.dma = data->dma;
 #endif
 
+       /* Set AP UART new register map */
+       writel(MTK_UART_FEAT_NEWRMAP, uart.port.membase +
+              (MTK_UART_FEATURE_SEL << uart.port.regshift));
+
        /* Disable Rate Fix function */
        writel(0x0, uart.port.membase +
                        (MTK_UART_RATE_FIX << uart.port.regshift));