Hi!
> From: Maciej W. Rozycki <macro@xxxxxxxxxxx>
>
> [ Upstream commit 9906890c89e4dbd900ed87ad3040080339a7f411 ]
>
> A SERIAL_8250_16550A_VARIANTS configuration option has been recently
> defined that lets one request the 8250 driver not to probe for 16550A
> device features so as to reduce the driver's device startup time in
> virtual machines.
>
> Some actual hardware devices require these features to have been fully
> determined however for their driver to work correctly, so define a flag
> to let drivers request full 16550A feature probing on a device-by-device
> basis if required regardless of the SERIAL_8250_16550A_VARIANTS option
> setting chosen.
>
> Fixes: dc56ecb81a0a ("serial: 8250: Support disabling mdelay-filled probes of 16550A variants")
> Cc: stable@xxxxxxxxxxxxxxx # v5.6+
You said you'd drop this. It is still unused in 5.10.155, as flag is
never set.
Best regards,
Pavel
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 8b3756e4bb05..f648fd1d7548 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -1023,7 +1023,8 @@ static void autoconfig_16550a(struct uart_8250_port *up)
> up->port.type = PORT_16550A;
> up->capabilities |= UART_CAP_FIFO;
>
> - if (!IS_ENABLED(CONFIG_SERIAL_8250_16550A_VARIANTS))
> + if (!IS_ENABLED(CONFIG_SERIAL_8250_16550A_VARIANTS) &&
> + !(up->port.flags & UPF_FULL_PROBE))
> return;
>
> /*
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 59a8caf3230a..6df4c3356ae6 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -100,7 +100,7 @@ struct uart_icount {
> __u32 buf_overrun;
> };
>
> -typedef unsigned int __bitwise upf_t;
> +typedef u64 __bitwise upf_t;
> typedef unsigned int __bitwise upstat_t;
>
> struct uart_port {
> @@ -207,6 +207,7 @@ struct uart_port {
> #define UPF_FIXED_PORT ((__force upf_t) (1 << 29))
> #define UPF_DEAD ((__force upf_t) (1 << 30))
> #define UPF_IOREMAP ((__force upf_t) (1 << 31))
> +#define UPF_FULL_PROBE ((__force upf_t) (1ULL << 32))
>
> #define __UPF_CHANGE_MASK 0x17fff
> #define UPF_CHANGE_MASK ((__force upf_t) __UPF_CHANGE_MASK)
--
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