Commit b4a29b94 authored by Lukas Wunner's avatar Lukas Wunner Committed by Greg Kroah-Hartman
Browse files

serial: 8250: Move Alpha-specific quirk out of the core 

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@mail.gmail.com/



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.

Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Ulrich Teichert <krypton@ulrich-teichert.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/b83d069cb516549b8a5420e097bb6bdd806f36fc.1640695609.git.lukas@wunner.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d3b3404d

drivers/tty/serial/8250/8250.h

+2 −10
Original line number Diff line number Diff line
@@ -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);

drivers/tty/serial/8250/8250_alpha.c

0 → 100644
+21 −0
Original line number Diff line number Diff line 
// 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);

}

drivers/tty/serial/8250/8250_core.c

+4 −5
Original line number Diff line number Diff line
@@ -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);

	}

drivers/tty/serial/8250/8250_port.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}

drivers/tty/serial/8250/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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