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

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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: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/b83d069cb516549b8a5420e097bb6bdd806f36fc.1640695609.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lukas Wunner 2021-12-28 18:22:00 +01:00 committed by Greg Kroah-Hartman
parent d3b3404df3
commit b4a29b9480
7 changed files with 32 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/tty/serial/8250/8250.h
View File

@ -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);

21
drivers/tty/serial/8250/8250_alpha.c Normal file
View File

@ -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);
}

9
drivers/tty/serial/8250/8250_core.c
View File

@ -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);
}

2
drivers/tty/serial/8250/8250_port.c
View File

@ -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);
}

2
drivers/tty/serial/8250/Makefile
View File

@ -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

3
drivers/tty/serial/sunsu.c
View File

@ -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;

2
include/linux/serial_8250.h
View File

@ -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