This is a note to let you know that I've just added the patch titled serial: 8250_mtk: Make sure to select the right FEATURE_SEL to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: serial-8250_mtk-make-sure-to-select-the-right-feature_sel.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 6f81fdded0d024c7d4084d434764f30bca1cd6b1 Mon Sep 17 00:00:00 2001 From: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> Date: Wed, 27 Apr 2022 15:23:27 +0200 Subject: serial: 8250_mtk: Make sure to select the right FEATURE_SEL From: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> commit 6f81fdded0d024c7d4084d434764f30bca1cd6b1 upstream. 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@xxxxxxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220427132328.228297-3-angelogioacchino.delregno@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/8250/8250_mtk.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -56,6 +56,9 @@ #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, @@ -554,6 +557,10 @@ 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)); Patches currently in stable-queue which might be from angelogioacchino.delregno@xxxxxxxxxxxxx are queue-5.4/serial-8250_mtk-make-sure-to-select-the-right-feature_sel.patch queue-5.4/serial-8250_mtk-fix-register-address-for-xon-xoff-character.patch queue-5.4/serial-8250_mtk-fix-uart_efr-register-address.patch