[PATCH 5.4 235/367] serial: sc16is7xx: fix broken port 0 uart init

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5.4-stable review patch.  If anyone has any objections, please let me know.


From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>

[ Upstream commit 2861ed4d6e6d1a2c9de9bf5b0abd996c2dc673d0 ]

The sc16is7xx_config_rs485() function is called only for the second
port (index 1, channel B), causing initialization problems for the
first port.

For the sc16is7xx driver, port->membase and port->mapbase are not set,
and their default values are 0. And we set port->iobase to the device
index. This means that when the first device is registered using the
uart_add_one_port() function, the following values will be in the port
    port->membase = 0
    port->mapbase = 0
    port->iobase  = 0

Therefore, the function uart_configure_port() in serial_core.c will
exit early because of the following check:
	 * If there isn't a port here, don't do anything further.
	if (!port->iobase && !port->mapbase && !port->membase)

Typically, I2C and SPI drivers do not set port->membase and

The max310x driver sets port->membase to ~0 (all ones). By
implementing the same change in this driver, uart_configure_port() is
now correctly executed for all ports.

Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Reviewed-by: Lech Perczak <lech.perczak@xxxxxxxxxxxxxxx>
Tested-by: Lech Perczak <lech.perczak@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230807214556.540627-2-hugo@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
 drivers/tty/serial/sc16is7xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 9b68725d4e9ba..091cf5fe90304 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1271,6 +1271,12 @@ static int sc16is7xx_probe(struct device *dev,
 		s->p[i].port.fifosize	= SC16IS7XX_FIFO_SIZE;
 		s->p[i].port.flags	= UPF_FIXED_TYPE | UPF_LOW_LATENCY;
 		s->p[i].port.iobase	= i;
+		/*
+		 * Use all ones as membase to make sure uart_configure_port() in
+		 * serial_core.c does not abort for SPI/I2C devices where the
+		 * membase address is not applicable.
+		 */
+		s->p[i].port.membase	= (void __iomem *)~0;
 		s->p[i].port.iotype	= UPIO_PORT;
 		s->p[i].port.uartclk	= freq;
 		s->p[i].port.rs485_config = sc16is7xx_config_rs485;

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