linux-kernel - [PATCH 5.15 220/230] Revert "serial: 8250_mtk: Make sure to select the right FEATURE

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Date:   Mon, 11 Jul 2022 11:07:56 +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>,
        "kernelci.org bot" <bot@...nelci.org>
Subject: [PATCH 5.15 220/230] Revert "serial: 8250_mtk: Make sure to select the right FEATURE_SEL"

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

commit f0136f65285bcfb7e8f90d1013723076a35acd51 upstream.

It was found that some MediaTek SoCs are incompatible with this
change. Also, this register was mistakenly understood as it was
related to the 16550A register layout selection but, at least
on some IPs, if not all, it's related to something else unknown.

This reverts commit 6f81fdded0d024c7d4084d434764f30bca1cd6b1.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Fixes: 6f81fdded0d0 ("serial: 8250_mtk: Make sure to select the right FEATURE_SEL")
Reported-by: "kernelci.org bot" <bot@...nelci.org>
Link: https://lore.kernel.org/r/20220510122620.150342-1-angelogioacchino.delregno@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/tty/serial/8250/8250_mtk.c |    7 -------
 1 file changed, 7 deletions(-)

--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -57,9 +57,6 @@
 #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,
@@ -575,10 +572,6 @@ static int mtk8250_probe(struct platform
 		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));