linux-kernel - [PATCH 5.15 136/230] serial: 8250_mtk: Make sure to select the right FEATURE

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Date:   Mon, 11 Jul 2022 11:06:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 136/230] serial: 8250_mtk: Make sure to select the right FEATURE_SEL

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

[ Upstream commit 6f81fdded0d024c7d4084d434764f30bca1cd6b1 ]

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@...labora.com>
Cc: stable <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20220427132328.228297-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/8250/8250_mtk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index de48a58460f4..de57f47635cd 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -57,6 +57,9 @@
 #define MTK_UART_XON1		40	/* I/O: Xon character 1 */
 #define MTK_UART_XOFF1		42	/* I/O: Xoff character 1 */
 
+#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,
@@ -572,6 +575,10 @@ 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));
-- 
2.35.1