From: AMEET M. PARANJAPE <aparanja@redhat.com>
Date: Fri, 23 Jan 2009 16:28:12 -0500
Subject: [ppc64] serial_core: define FIXED_PORT flag
Message-id: 20090123212700.11116.80247.sendpatchset@squad5-lp1.lab.bos.redhat.com
O-Subject: [PATCH RHEL5.4 BZ475621] define FIXED_PORT flag for serial_core
Bugzilla: 475621
RH-Acked-by: David Howells <dhowells@redhat.com>
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>
RH-Acked-by: Aristeu Rozanski <aris@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=475621

Description:
===========
At present, the serial core always allows setserial in userspace to change the
port address, irq and base clock of any serial port.  That makes sense for
legacy ISA ports, but not for (say) embedded ns16550 compatible serial ports
at peculiar addresses.  In these cases, the kernel code configuring the ports
must know exactly where they are, and their clocking arrangements (which can
be unusual on embedded boards).  It doesn't make sense for userspace to change
these settings.

Therefore, this patch defines a UPF_FIXED_PORT flag for the uart_port
structure.  If this flag is set when the serial port is configured, any
attempts to alter the port's type, io address, irq or base clock with
setserial are ignored.

In addition this patch uses the new flag for on-chip serial ports probed in
arch/powerpc/kernel/legacy_serial.c, and for other hard-wired serial ports
probed by drivers/serial/of_serial.c.

RHEL Version Found:
================
RHEL 5.3

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1661130

Upstream Status:
================
GIT Commit ID abb4a2390737867353ebafc012d45f2b03f3f944

Test Status:
============
Without this patch the QS2* serial over lan (SOL) console results in a garbled
output to the screen.  The work around was to provide the
'console=ttyS0,19200' at the linux boot prompt and then changing the
/etc/inittab entry to include
'tty:2345:respawn:/sbin/agetty ttyS0 19200 vt100-nav'.

With this patch the workaround entries are no longer required and SOL works
by default.

===============================================================
Ameet Paranjape 978-392-3903 ext 23903
IBM on-site partner

Proposed Patch:
===============

diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
index dfd2bd6..abf244a 100644
--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c
@@ -114,7 +114,8 @@ static int __init add_legacy_soc_port(struct device_node *np,
 {
 	u64 addr;
 	u32 *addrp;
-	upf_t flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_SHARE_IRQ;
+	upf_t flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_SHARE_IRQ
+		| UPF_FIXED_PORT;
 	struct device_node *tsi = of_get_parent(np);
 
 	/* We only support ports that have a clock frequency properly
diff --git a/drivers/serial/of_serial.c b/drivers/serial/of_serial.c
index e2b1f2e..eea02a5 100644
--- a/drivers/serial/of_serial.c
+++ b/drivers/serial/of_serial.c
@@ -48,7 +48,8 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
 	port->iotype = UPIO_MEM;
 	port->type = type;
 	port->uartclk = *clk;
-	port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP;
+	port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP
+		| UPF_FIXED_PORT;
 	port->dev = &ofdev->dev;
 	port->custom_divisor = *clk / (16 * (*spd));
 
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 5dc8fce..b80c760 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -683,19 +683,21 @@ static int uart_set_info(struct uart_state *state,
 	 */
 	mutex_lock(&state->mutex);
 
-	change_irq  = new_serial.irq != port->irq;
+	change_irq  = !(port->flags & UPF_FIXED_PORT)
+		&& new_serial.irq != port->irq;
 
 	/*
 	 * Since changing the 'type' of the port changes its resource
 	 * allocations, we should treat type changes the same as
 	 * IO port changes.
 	 */
-	change_port = new_port != port->iobase ||
-		      (unsigned long)new_serial.iomem_base != port->mapbase ||
-		      new_serial.hub6 != port->hub6 ||
-		      new_serial.io_type != port->iotype ||
-		      new_serial.iomem_reg_shift != port->regshift ||
-		      new_serial.type != port->type;
+	change_port = !(port->flags & UPF_FIXED_PORT)
+		&& (new_port != port->iobase ||
+		    (unsigned long)new_serial.iomem_base != port->mapbase ||
+		    new_serial.hub6 != port->hub6 ||
+		    new_serial.io_type != port->iotype ||
+		    new_serial.iomem_reg_shift != port->regshift ||
+		    new_serial.type != port->type);
 
 	old_flags = port->flags;
 	new_flags = new_serial.flags;
@@ -806,8 +808,10 @@ static int uart_set_info(struct uart_state *state,
 		}
 	}
 
-	port->irq              = new_serial.irq;
-	port->uartclk          = new_serial.baud_base * 16;
+	if (change_irq)
+		port->irq      = new_serial.irq;
+	if (!(port->flags & UPF_FIXED_PORT))
+		port->uartclk  = new_serial.baud_base * 16;
 	port->flags            = (port->flags & ~UPF_CHANGE_MASK) |
 				 (new_flags & UPF_CHANGE_MASK);
 	port->custom_divisor   = new_serial.custom_divisor;
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 3fad04f..00443cd 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -258,6 +258,7 @@ struct uart_port {
 #define UPF_CONS_FLOW		((__force upf_t) (1 << 23))
 #define UPF_SHARE_IRQ		((__force upf_t) (1 << 24))
 #define UPF_BOOT_AUTOCONF	((__force upf_t) (1 << 28))
+#define UPF_FIXED_PORT		((__force upf_t) (1 << 29))
 #define UPF_DEAD		((__force upf_t) (1 << 30))
 #define UPF_IOREMAP		((__force upf_t) (1 << 31))