On 28. 12. 21, 18:22, Lukas Wunner wrote:
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* Fix outdated reference to the quirk in sunsu.c.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()))
It'd be definitely nicer, if here was only "if (alpha_jensen())". The
rest would be done in the header or in 8250_alpha.c.
Or even create an empty __weak arch_serial8250_set_defaults() and also
one non-empty in arch/alpha/?
thanks,
--
js
suse labs
