* [PATCH v2] serial: 8250: Move Alpha-specific quirk out of the core
@ 2021-12-28 17:22 Lukas Wunner
2022-01-04 7:17 ` Jiri Slaby
0 siblings, 1 reply; 2+ messages in thread
From: Lukas Wunner @ 2021-12-28 17:22 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby
Cc: linux-serial, Russell King, Ulrich Teichert, Linus Torvalds,
Richard Henderson, Ivan Kokshaysky, Matt Turner, linux-alpha,
Lino Sanfilippo, Philipp Rosenberger, John Paul Adrian Glaubitz
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.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Ulrich Teichert <krypton@ulrich-teichert.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
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* Fix outdated reference to the quirk in sunsu.c.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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] serial: 8250: Move Alpha-specific quirk out of the core
2021-12-28 17:22 [PATCH v2] serial: 8250: Move Alpha-specific quirk out of the core Lukas Wunner
@ 2022-01-04 7:17 ` Jiri Slaby
0 siblings, 0 replies; 2+ messages in thread
From: Jiri Slaby @ 2022-01-04 7:17 UTC (permalink / raw)
To: Lukas Wunner, Greg Kroah-Hartman
Cc: linux-serial, Russell King, Ulrich Teichert, Linus Torvalds,
Richard Henderson, Ivan Kokshaysky, Matt Turner, linux-alpha,
Lino Sanfilippo, Philipp Rosenberger, John Paul Adrian Glaubitz
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@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.
>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Cc: Russell King <rmk+kernel@armlinux.org.uk>
> Cc: Ulrich Teichert <krypton@ulrich-teichert.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> ---
> 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
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