struct uart_8250_port contains mcr_mask and mcr_force members whose sole purpose is to work around an Alpha-specific quirk. This code doesn't belong in the core where it is executed by everyone else, so move it to a proper ->set_mctrl callback which is used on the affected Alpha machine only. The quirk was introduced in January 1995: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/drivers/char/serial.c?h=1.1.83 The members in struct uart_8250_port were added in 2002: https://git.kernel.org/history/history/c/4524aad27854 The quirk applies to non-PCI Alphas and arch/alpha/Kconfig specifies "select FORCE_PCI if !ALPHA_JENSEN". So apparently the only affected machine is the EISA-based Jensen that Linus was working on back then: https://lore.kernel.org/all/CAHk-=wj1JWZ3sCrGz16nxEj7=0O+srMg6Ah3iPTDXSPKEws_SA@xxxxxxxxxxxxxx/ Up until now the quirk is not applied unless CONFIG_PCI is disabled. If users forget to do that or run a generic Alpha kernel, the serial ports aren't usable on Jensen. Avoid by confining the quirk to CONFIG_ALPHA_JENSEN instead of !CONFIG_PCI. On generic Alpha kernels, auto-detect at runtime whether the quirk needs to be applied. Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> Cc: Ulrich Teichert <krypton@xxxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> --- Changes in v2: * Also apply quirk when running a generic Alpha kernel on a Jensen. * Fix outdated reference to the quirk in sunsu.c. drivers/tty/serial/8250/8250.h | 12 ++---------- drivers/tty/serial/8250/8250_alpha.c | 21 +++++++++++++++++++++ drivers/tty/serial/8250/8250_core.c | 9 ++++----- drivers/tty/serial/8250/8250_port.c | 2 +- drivers/tty/serial/8250/Makefile | 2 ++ drivers/tty/serial/sunsu.c | 3 ++- include/linux/serial_8250.h | 2 -- 7 files changed, 32 insertions(+), 19 deletions(-) create mode 100644 drivers/tty/serial/8250/8250_alpha.c diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index 6473361525d1..db784ace25d8 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -241,16 +241,8 @@ static inline int serial8250_in_MCR(struct uart_8250_port *up) return mctrl; } -#if defined(__alpha__) && !defined(CONFIG_PCI) -/* - * Digital did something really horribly wrong with the OUT1 and OUT2 - * lines on at least some ALPHA's. The failure mode is that if either - * is cleared, the machine locks up with endless interrupts. - */ -#define ALPHA_KLUDGE_MCR (UART_MCR_OUT2 | UART_MCR_OUT1) -#else -#define ALPHA_KLUDGE_MCR 0 -#endif +bool alpha_jensen(void); +void alpha_jensen_set_mctrl(struct uart_port *port, unsigned int mctrl); #ifdef CONFIG_SERIAL_8250_PNP int serial8250_pnp_init(void); diff --git a/drivers/tty/serial/8250/8250_alpha.c b/drivers/tty/serial/8250/8250_alpha.c new file mode 100644 index 000000000000..58e70328aa4d --- /dev/null +++ b/drivers/tty/serial/8250/8250_alpha.c @@ -0,0 +1,21 @@ +// SPDX-License-Identifier: GPL-2.0+ + +#include <asm/machvec.h> +#include "8250.h" + +bool alpha_jensen(void) +{ + return !strcmp(alpha_mv.vector_name, "Jensen"); +} + +void alpha_jensen_set_mctrl(struct uart_port *port, unsigned int mctrl) +{ + /* + * Digital did something really horribly wrong with the OUT1 and OUT2 + * lines on Alpha Jensen. The failure mode is that if either is + * cleared, the machine locks up with endless interrupts. + */ + mctrl |= TIOCM_OUT1 | TIOCM_OUT2; + + serial8250_do_set_mctrl(port, mctrl); +} diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 1ce193daea7f..01d30f6ed8fb 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -509,11 +509,10 @@ static void __init serial8250_isa_init_ports(void) up->ops = &univ8250_driver_ops; - /* - * ALPHA_KLUDGE_MCR needs to be killed. - */ - up->mcr_mask = ~ALPHA_KLUDGE_MCR; - up->mcr_force = ALPHA_KLUDGE_MCR; + if (IS_ENABLED(CONFIG_ALPHA_JENSEN) || + (IS_ENABLED(CONFIG_ALPHA_GENERIC) && alpha_jensen())) + port->set_mctrl = alpha_jensen_set_mctrl; + serial8250_set_defaults(up); } diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 5d9a0e9f75d4..3b12bfc1ed67 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2026,7 +2026,7 @@ void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl) mcr = serial8250_TIOCM_to_MCR(mctrl); - mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr; + mcr |= up->mcr; serial8250_out_MCR(up, mcr); } diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile index 4e4913e0e4d2..bee908f99ea0 100644 --- a/drivers/tty/serial/8250/Makefile +++ b/drivers/tty/serial/8250/Makefile @@ -5,6 +5,8 @@ obj-$(CONFIG_SERIAL_8250) += 8250.o 8250_base.o 8250-y := 8250_core.o +8250-$(CONFIG_ALPHA_GENERIC) += 8250_alpha.o +8250-$(CONFIG_ALPHA_JENSEN) += 8250_alpha.o 8250-$(CONFIG_SERIAL_8250_PNP) += 8250_pnp.o 8250_base-y := 8250_port.o 8250_base-$(CONFIG_SERIAL_8250_DMA) += 8250_dma.o diff --git a/drivers/tty/serial/sunsu.c b/drivers/tty/serial/sunsu.c index 425a016f9db7..98b2f4fb9a99 100644 --- a/drivers/tty/serial/sunsu.c +++ b/drivers/tty/serial/sunsu.c @@ -127,7 +127,8 @@ static void serial_out(struct uart_sunsu_port *up, int offset, int value) * gate outputs a logical one. Since we use level triggered interrupts * we have lockup and watchdog reset. We cannot mask IRQ because * keyboard shares IRQ with us (Word has it as Bob Smelik's design). - * This problem is similar to what Alpha people suffer, see serial.c. + * This problem is similar to what Alpha people suffer, see + * 8250_alpha.c. */ if (offset == UART_MCR) value |= UART_MCR_OUT2; diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index 5db211f43b29..ff84a3ed10ea 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -104,8 +104,6 @@ struct uart_8250_port { unsigned char ier; unsigned char lcr; unsigned char mcr; - unsigned char mcr_mask; /* mask of user bits */ - unsigned char mcr_force; /* mask of forced bits */ unsigned char cur_iotype; /* Running I/O type */ unsigned int rpm_tx_active; unsigned char canary; /* non-zero during system sleep -- 2.33.0
