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: 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>

diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 6473361525d1f792868db6117bd7c4555845a319..db784ace25d83bef20f591ce26287eefece705bc 100644 (file)
--- 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 (file)
index 0000000..58e7032
--- /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 1ce193daea7f15407e3d29d4ec2f4bae7dbb2791..01d30f6ed8fb59312664c269b97b310b4791e1d7 100644 (file)
--- 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 7e7e67dea0ad1d0b5240954840af2bcd83aa32b0..2abb3de11a48b183c22808be30ae8597eea5e614 100644 (file)
--- 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 4e4913e0e4d2c119d1e93aa780daacab9bdbfb5e..bee908f99ea0e81877747d9b56d9ff6ef3d42472 100644 (file)
--- 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 425a016f9db7a0b0df9614c90c9e9ebdb7ea14f8..98b2f4fb9a99b8e84b3b6739860bfacf937cea0e 100644 (file)
--- 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 5db211f43b29ec870f2bc063c7ac7ba84a48f29d..ff84a3ed10ea911c742978ba01863052d8d6a4ab 100644 (file)
--- 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