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Message-ID: <Pine.LNX.4.64N.0705311023100.7856@blysk.ds.pg.gda.pl>
Date: Thu, 31 May 2007 11:04:53 +0100 (BST)
From: "Maciej W. Rozycki" <macro@...ux-mips.org>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: linux-mips@...ux-mips.org, linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] zs: Updates to fix issues raised
This is a set of fixes to the initial revision of the zs driver port to
the serial subsystem. They include an update to the recovery delay, and
the race on interrupt handler registration. As well as a number of style
fixes throughout.
Signed-off-by: Maciej W. Rozycki <macro@...ux-mips.org>
---
Andrew,
It looks like port_sem is not enough to protect against a race in the
startup() call -- while the serial API spec refers to it as "an overall
semaphore" as opposed to "per-port" as it documents the other locks, the
actual code contradicts it. ;-) I had to resist the temptation to use
scc->zlock here as it leads to a spinlock recursion and hence a deadlock.
The reason is with CONFIG_DEBUG_SHIRQ a call to zs_interrupt() is made
from beneath request_irq() even though local interrupts are disabled.
I'm not sure if it is intentional, a design limitation or a bug. Anyway,
using an atomic counter is better as it makes the duration of interrupts
being disabled shorter.
In the end I have not added the CON_BOOT flag, because this is a
full-featured console driver, not an early one. I have not updated
printk() calls in zs_dump() either -- I figured out adding pr_info("")
calls before the loops would add little value. I fixed the other instance
though.
Removing "inline" clauses reduced the text size by about 50% ;-) and
branches are essentially free on the R3000 and not that horribly expensive
on the R4000/R4400 either -- which exhaust the possible CPU configurations
for this driver at the moment (one day this driver could be used for DEC
3000 AXP systems as well as they reuse the same setup of these bits).
Please apply.
Maciej
patch-2.6.22-rc2-serial-zs-fix-4
diff -up --recursive --new-file linux-2.6.22-rc2.macro/drivers/serial/zs.c linux-2.6.22-rc2/drivers/serial/zs.c
--- linux-2.6.22-rc2.macro/drivers/serial/zs.c 2007-05-29 12:42:14.000000000 +0000
+++ linux-2.6.22-rc2/drivers/serial/zs.c 2007-05-30 22:25:42.000000000 +0000
@@ -47,11 +47,13 @@
#define SUPPORT_SYSRQ
#endif
+#include <linux/bug.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/interrupt.h>
+#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/irqflags.h>
#include <linux/kernel.h>
@@ -62,8 +64,7 @@
#include <linux/sysrq.h>
#include <linux/tty.h>
-#include <asm/bug.h>
-#include <asm/io.h>
+#include <asm/atomic.h>
#include <asm/system.h>
#include <asm/dec/interrupts.h>
@@ -86,11 +87,10 @@ static char zs_version[] __initdata = "0
#define ZS_CHAN_B 1 /* Index of the channel B. */
#define ZS_CHAN_IO_SIZE 8 /* IOMEM space size. */
#define ZS_CHAN_IO_STRIDE 4 /* Register alignment. */
-#define ZS_CHAN_IO_OFFSET 1 /* The SCC resides on the high byte of the 16-bit IOBUS. */
+#define ZS_CHAN_IO_OFFSET 1 /* The SCC resides on the high byte
+ of the 16-bit IOBUS. */
#define ZS_CLOCK 7372800 /* Z85C30 PCLK input clock rate. */
-#define RECOVERY_DELAY udelay(2)
-
#define to_zport(uport) container_of(uport, struct zs_port, port)
struct zs_parms {
@@ -126,53 +126,59 @@ static u8 zs_init_regs[ZS_NUM_REGS] __in
/*
* Reading and writing Z85C30 registers.
*/
-static inline u8 read_zsreg(struct zs_port *zport, int reg)
+static void recovery_delay(void)
+{
+ udelay(2);
+}
+
+static u8 read_zsreg(struct zs_port *zport, int reg)
{
- volatile void __iomem *control = zport->port.membase +
- ZS_CHAN_IO_OFFSET;
+ void __iomem *control = zport->port.membase + ZS_CHAN_IO_OFFSET;
u8 retval;
if (reg != 0) {
writeb(reg & 0xf, control);
- fast_iob(); RECOVERY_DELAY;
+ fast_iob();
+ recovery_delay();
}
retval = readb(control);
- RECOVERY_DELAY;
+ recovery_delay();
return retval;
}
-static inline void write_zsreg(struct zs_port *zport, int reg, u8 value)
+static void write_zsreg(struct zs_port *zport, int reg, u8 value)
{
- volatile void __iomem *control = zport->port.membase +
- ZS_CHAN_IO_OFFSET;
+ void __iomem *control = zport->port.membase + ZS_CHAN_IO_OFFSET;
if (reg != 0) {
writeb(reg & 0xf, control);
- fast_iob(); RECOVERY_DELAY;
+ fast_iob(); recovery_delay();
}
writeb(value, control);
- fast_iob(); RECOVERY_DELAY;
+ fast_iob();
+ recovery_delay();
return;
}
-static inline u8 read_zsdata(struct zs_port *zport)
+static u8 read_zsdata(struct zs_port *zport)
{
- volatile void __iomem *data = zport->port.membase +
- ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
+ void __iomem *data = zport->port.membase +
+ ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
u8 retval;
retval = readb(data);
- RECOVERY_DELAY;
+ recovery_delay();
return retval;
}
-static inline void write_zsdata(struct zs_port *zport, u8 value)
+static void write_zsdata(struct zs_port *zport, u8 value)
{
- volatile void __iomem *data = zport->port.membase +
- ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
+ void __iomem *data = zport->port.membase +
+ ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
writeb(value, data);
- fast_iob(); RECOVERY_DELAY;
+ fast_iob();
+ recovery_delay();
return;
}
@@ -196,7 +202,7 @@ void zs_dump(void)
#endif
-static inline void zs_spin_lock_cond_irq(spinlock_t* lock, int irq)
+static void zs_spin_lock_cond_irq(spinlock_t *lock, int irq)
{
if (irq)
spin_lock_irq(lock);
@@ -204,7 +210,7 @@ static inline void zs_spin_lock_cond_irq
spin_lock(lock);
}
-static inline void zs_spin_unlock_cond_irq(spinlock_t* lock, int irq)
+static void zs_spin_unlock_cond_irq(spinlock_t *lock, int irq)
{
if (irq)
spin_unlock_irq(lock);
@@ -235,7 +241,7 @@ static int zs_transmit_drain(struct zs_p
}
-static inline void load_zsregs(struct zs_port *zport, u8 *regs, int irq)
+static void load_zsregs(struct zs_port *zport, u8 *regs, int irq)
{
zs_transmit_drain(zport, irq);
/* Load 'em up. */
@@ -288,8 +294,8 @@ static unsigned int zs_tx_empty(struct u
return status & ALL_SNT ? TIOCSER_TEMT : 0;
}
-static inline unsigned int zs_raw_get_ab_mctrl(struct zs_port *zport_a,
- struct zs_port *zport_b)
+static unsigned int zs_raw_get_ab_mctrl(struct zs_port *zport_a,
+ struct zs_port *zport_b)
{
u8 status_a, status_b;
unsigned int mctrl;
@@ -728,18 +734,20 @@ static int zs_startup(struct uart_port *
struct zs_port *zport = to_zport(uport);
struct zs_scc *scc = zport->scc;
unsigned long flags;
+ int irq_guard;
int ret;
- if (!scc->irq_guard) {
+ irq_guard = atomic_add_return(1, &scc->irq_guard);
+ if (irq_guard == 1) {
ret = request_irq(zport->port.irq, zs_interrupt,
IRQF_SHARED, "scc", scc);
if (ret) {
+ atomic_add(-1, &scc->irq_guard);
printk(KERN_ERR "zs: can't get irq %d\n",
zport->port.irq);
return ret;
}
}
- scc->irq_guard++;
spin_lock_irqsave(&scc->zlock, flags);
@@ -780,6 +788,7 @@ static void zs_shutdown(struct uart_port
struct zs_port *zport = to_zport(uport);
struct zs_scc *scc = zport->scc;
unsigned long flags;
+ int irq_guard;
spin_lock_irqsave(&scc->zlock, flags);
@@ -790,8 +799,8 @@ static void zs_shutdown(struct uart_port
spin_unlock_irqrestore(&scc->zlock, flags);
- scc->irq_guard--;
- if (!scc->irq_guard)
+ irq_guard = atomic_add_return(-1, &scc->irq_guard);
+ if (!irq_guard)
free_irq(zport->port.irq, scc);
}
@@ -1203,7 +1212,7 @@ static int __init zs_init(void)
{
int i, ret;
- printk("%s%s\n", zs_name, zs_version);
+ pr_info("%s%s\n", zs_name, zs_version);
/* Find out how many Z85C30 SCCs we have. */
ret = zs_probe_sccs();
diff -up --recursive --new-file linux-2.6.22-rc2.macro/drivers/serial/zs.h linux-2.6.22-rc2/drivers/serial/zs.h
--- linux-2.6.22-rc2.macro/drivers/serial/zs.h 2007-05-29 12:34:38.000000000 +0000
+++ linux-2.6.22-rc2/drivers/serial/zs.h 2007-05-30 21:28:27.000000000 +0000
@@ -39,7 +39,7 @@ struct zs_port {
struct zs_scc {
struct zs_port zport[2];
spinlock_t zlock;
- int irq_guard;
+ atomic_t irq_guard;
int initialised;
};
-
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