Hi Gregory.
On Wed, Feb 27, 2013 at 05:08:04PM +0100, Gregory CLEMENT wrote:
> I found the root of the problem in drivers/tty/serial/8250/8250.c
>
> in the autoconfig() function, when the IIR register is acceded, it is
> done using serial_in(), this function return an int but is used as it
> have returned a char. There is a lot of implicit cast to a char when
> the returned value is put in a char variable, this seems to not be a
> problem most of the time. The problematic line is the following:
>
> scratch = serial_in(up, UART_IIR) >> 6;
>
> the shift is done here before any cast or mask, and unfortunately my
> hardware send 0xC1C1C1C1, that lead to get a '7' in the scratch
> variable instead of a '3'.
OK, this is interesting. Why does it return that? dw_apb_uart_db.pdf I
have says that bits 31:8 read as zero?
> Would you agree with this kind of patch to fix the issue?
>
> diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
> index e2ac25a..0b284c6 100644
> --- a/drivers/tty/serial/8250/8250.c
> +++ b/drivers/tty/serial/8250/8250.c
> @@ -1119,7 +1119,7 @@ static void autoconfig(struct uart_8250_port *up,
> unsigned int probeflags)
> serial_out(up, UART_LCR, 0);
>
> serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
> - scratch = serial_in(up, UART_IIR) >> 6;
> + scratch = (serial_in(up, UART_IIR) & 0xFF) >> 6;
>
> switch (scratch) {
> case 0:
Instead, can you test if it's enough for you to set the reg-io-width
to 1 instead of 4:
diff --git a/arch/arm/boot/dts/armada-370-xp.dtsi
b/arch/arm/boot/dts/armada-370-xp.dtsi
index 4c0abe8..3a87a0e 100644
--- a/arch/arm/boot/dts/armada-370-xp.dtsi
+++ b/arch/arm/boot/dts/armada-370-xp.dtsi
@@ -54,7 +54,7 @@
reg = <0xd0012000 0x100>;
reg-shift = <2>;
interrupts = <41>;
- reg-io-width = <4>;
+ reg-io-width = <1>;
status = "disabled";
};
serial@d0012100 {
@@ -62,7 +62,7 @@
reg = <0xd0012100 0x100>;
reg-shift = <2>;
interrupts = <42>;
- reg-io-width = <4>;
+ reg-io-width = <1>;
status = "disabled";
};
Thanks,
--
heikki
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
