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- From 629c701fc39f1ada9416e0766a86729e83bde86c Mon Sep 17 00:00:00 2001
- Message-ID: <629c701fc39f1ada9416e0766a86729e83bde86c.1694465766.git.daniel@makrotopia.org>
- From: Daniel Golle <[email protected]>
- Date: Mon, 11 Sep 2023 21:27:44 +0100
- Subject: [PATCH] serial: 8250_mtk: track busclk state to avoid bus error
- To: Greg Kroah-Hartman <[email protected]>,
- Jiri Slaby <[email protected]>,
- Matthias Brugger <[email protected]>,
- AngeloGioacchino Del Regno <[email protected]>,
- Daniel Golle <[email protected]>,
- John Ogness <[email protected]>,
- Chen-Yu Tsai <[email protected]>,
- Changqi Hu <[email protected]>,
- [email protected],
- [email protected],
- [email protected],
- [email protected]
- Commit e32a83c70cf9 ("serial: 8250-mtk: modify mtk uart power and
- clock management") introduced polling a debug register to make sure
- the UART is idle before disabling the bus clock. However, at least on
- some MediaTek SoCs access to that very debug register requires the bus
- clock being enabled. Hence calling the suspend function while already
- in suspended state results in that register access triggering a bus
- error. In order to avoid that, track the state of the bus clock and
- only poll the debug register if not already in suspended state.
- Fixes: e32a83c70cf9 ("serial: 8250-mtk: modify mtk uart power and clock management")
- Signed-off-by: Daniel Golle <[email protected]>
- ---
- drivers/tty/serial/8250/8250_mtk.c | 11 ++++++++++-
- 1 file changed, 10 insertions(+), 1 deletion(-)
- --- a/drivers/tty/serial/8250/8250_mtk.c
- +++ b/drivers/tty/serial/8250/8250_mtk.c
- @@ -32,7 +32,7 @@
- #define MTK_UART_RXTRI_AD 0x14 /* RX Trigger address */
- #define MTK_UART_FRACDIV_L 0x15 /* Fractional divider LSB address */
- #define MTK_UART_FRACDIV_M 0x16 /* Fractional divider MSB address */
- -#define MTK_UART_DEBUG0 0x18
- +#define MTK_UART_DEBUG0 0x18
- #define MTK_UART_IER_XOFFI 0x20 /* Enable XOFF character interrupt */
- #define MTK_UART_IER_RTSI 0x40 /* Enable RTS Modem status interrupt */
- #define MTK_UART_IER_CTSI 0x80 /* Enable CTS Modem status interrupt */
- @@ -418,13 +418,12 @@ static int __maybe_unused mtk8250_runtim
- struct mtk8250_data *data = dev_get_drvdata(dev);
- struct uart_8250_port *up = serial8250_get_port(data->line);
-
- - /* wait until UART in idle status */
- - while
- - (serial_in(up, MTK_UART_DEBUG0));
- -
- if (data->clk_count == 0U) {
- dev_dbg(dev, "%s clock count is 0\n", __func__);
- } else {
- + /* wait until UART in idle status */
- + while
- + (serial_in(up, MTK_UART_DEBUG0));
- clk_disable_unprepare(data->bus_clk);
- data->clk_count--;
- }
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