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Re: [PATCH] serial_txx9: forcibly init the spinlock for PCI UART used as

To: sshtylyov@dev.rtsoft.ru
Subject: Re: [PATCH] serial_txx9: forcibly init the spinlock for PCI UART used as a console
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Wed, 28 Dec 2005 13:25:44 +0900 (JST)
Cc: rmk@arm.linux.org.uk, linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <43B196A9.8010608@dev.rtsoft.ru> <20051227184152.GA4474@flint.arm.linux.org.uk>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20051227184152.GA4474@flint.arm.linux.org.uk> <43B18DD2.3090206@ru.mvista.com> <43B196A9.8010608@dev.rtsoft.ru>
Sender: linux-mips-bounce@linux-mips.org
>>>>> On Tue, 27 Dec 2005 18:41:52 +0000, Russell King <rmk@arm.linux.org.uk> 
>>>>> said:
rmk> This should result in a cleaner implementation, and the console
rmk> will not be started until you detect the PCI card.  Which is the
rmk> behaviour you desire in any case.

Thanks for your advise.  Though this is not fix the problem as Sergei
said, I would refine the driver.

>>>>> On Tue, 27 Dec 2005 22:31:53 +0300, Sergei Shtylyov 
>>>>> <sshtylyov@dev.rtsoft.ru> said:
sshtylyov>     All in all, the problem of uninit'ed PCI port spinlock
sshtylyov> will remain unless serial core is fixed (ot at least the
sshtylyov> driver). Proposed driver re-design wouldn't help as this is
sshtylyov> actually chicken-before-egg type problem --
sshtylyov> uart_add_one_port() assumes that the console is setup
sshtylyov> beforehand, and this just can't happen in case of a PCI
sshtylyov> card.

I agree.  Let me clarify a situation.

* The serial_txx9 driver handles both SOC UARTs and PCI UARTs.

* We want to use console_initcall to register console for SOC UARTs.

* PCI UARTs were not detected when console_initcall function was called.

* For PCI UARTs, uart_add_one_port() calls register_console (again)
  _after_ configuring the port.  The spinlock must be initialized
  before configure the port.

* By first register_console, port->cons->index has been
  initialized. (even if console setup function failed)

* The uart_console() returns 1 even if the console was not
  successfully configured (CON_ENABLED was not set and spinlock did
  not initialized).  So uart_add_one_port() does not initialize the
  spinlock for the console.

There would be 3 solutions:

1. uart_add_one_port() initialize the spinlock for console port
   without CON_ENABLED.

2. lowlevel driver initialize the spinlock somewhere.

3. register_console() revert console->index to -1 when console->setup
   function failed.  (But register_console is already too complex for
   me ...)

I would prefer (1), but if not acceptable, I do not object to (2).


This is a refined patch following Russell's advise.  This does not
include Sergei's fix.

 * More strict check in verify_port.  Cleanup.
 * Do not insert a char caused previous overrun.
 * Fix some spin_locks.
 * Do not call uart_add_one_port for absent ports.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

diff --git a/drivers/serial/serial_txx9.c b/drivers/serial/serial_txx9.c
index f10c86d..37fa0aa 100644
--- a/drivers/serial/serial_txx9.c
+++ b/drivers/serial/serial_txx9.c
@@ -33,6 +33,10 @@
  *     1.02    Cleanup. (import 8250.c changes)
  *     1.03    Fix low-latency mode. (import 8250.c changes)
  *     1.04    Remove usage of deprecated functions, cleanup.
+ *     1.05    More strict check in verify_port.  Cleanup.
+ *     1.06    Do not insert a char caused previous overrun.
+ *             Fix some spin_locks.
+ *             Do not call uart_add_one_port for absent ports.
  */
 #include <linux/config.h>
 
@@ -56,7 +60,7 @@
 #include <asm/io.h>
 #include <asm/irq.h>
 
-static char *serial_version = "1.04";
+static char *serial_version = "1.06";
 static char *serial_name = "TX39/49 Serial driver";
 
 #define PASS_LIMIT     256
@@ -209,7 +213,7 @@ static inline unsigned int sio_in(struct
 {
        switch (up->port.iotype) {
        default:
-               return *(volatile u32 *)(up->port.membase + offset);
+               return __raw_readl(up->port.membase + offset);
        case UPIO_PORT:
                return inl(up->port.iobase + offset);
        }
@@ -220,7 +224,7 @@ sio_out(struct uart_txx9_port *up, int o
 {
        switch (up->port.iotype) {
        default:
-               *(volatile u32 *)(up->port.membase + offset) = value;
+               __raw_writel(value, up->port.membase + offset);
                break;
        case UPIO_PORT:
                outl(value, up->port.iobase + offset);
@@ -258,34 +262,19 @@ sio_quot_set(struct uart_txx9_port *up, 
 static void serial_txx9_stop_tx(struct uart_port *port)
 {
        struct uart_txx9_port *up = (struct uart_txx9_port *)port;
-       unsigned long flags;
-
-       spin_lock_irqsave(&up->port.lock, flags);
        sio_mask(up, TXX9_SIDICR, TXX9_SIDICR_TIE);
-       spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static void serial_txx9_start_tx(struct uart_port *port)
 {
        struct uart_txx9_port *up = (struct uart_txx9_port *)port;
-       unsigned long flags;
-
-       spin_lock_irqsave(&up->port.lock, flags);
        sio_set(up, TXX9_SIDICR, TXX9_SIDICR_TIE);
-       spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static void serial_txx9_stop_rx(struct uart_port *port)
 {
        struct uart_txx9_port *up = (struct uart_txx9_port *)port;
-       unsigned long flags;
-
-       spin_lock_irqsave(&up->port.lock, flags);
        up->port.read_status_mask &= ~TXX9_SIDISR_RDIS;
-#if 0
-       sio_mask(up, TXX9_SIDICR, TXX9_SIDICR_RIE);
-#endif
-       spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static void serial_txx9_enable_ms(struct uart_port *port)
@@ -301,6 +290,7 @@ receive_chars(struct uart_txx9_port *up,
        unsigned int disr = *status;
        int max_count = 256;
        char flag;
+       unsigned int next_ignore_status_mask;
 
        do {
                /* The following is not allowed by the tty layer and
@@ -318,6 +308,9 @@ receive_chars(struct uart_txx9_port *up,
                flag = TTY_NORMAL;
                up->port.icount.rx++;
 
+               /* mask out RFDN_MASK bit added by previous overrun */
+               next_ignore_status_mask =
+                       up->port.ignore_status_mask & ~TXX9_SIDISR_RFDN_MASK;
                if (unlikely(disr & (TXX9_SIDISR_UBRK | TXX9_SIDISR_UPER |
                                     TXX9_SIDISR_UFER | TXX9_SIDISR_UOER))) {
                        /*
@@ -338,8 +331,17 @@ receive_chars(struct uart_txx9_port *up,
                                up->port.icount.parity++;
                        else if (disr & TXX9_SIDISR_UFER)
                                up->port.icount.frame++;
-                       if (disr & TXX9_SIDISR_UOER)
+                       if (disr & TXX9_SIDISR_UOER) {
                                up->port.icount.overrun++;
+                               /*
+                                * The receiver read buffer still hold
+                                * a char which caused overrun.
+                                * Ignore next char by adding RFDN_MASK
+                                * to ignore_status_mask temporarily.
+                                */
+                               next_ignore_status_mask |=
+                                       TXX9_SIDISR_RFDN_MASK;
+                       }
 
                        /*
                         * Mask off conditions which should be ingored.
@@ -359,6 +361,7 @@ receive_chars(struct uart_txx9_port *up,
                uart_insert_char(&up->port, disr, TXX9_SIDISR_UOER, ch, flag);
 
        ignore_char:
+               up->port.ignore_status_mask = next_ignore_status_mask;
                disr = sio_in(up, TXX9_SIDISR);
        } while (!(disr & TXX9_SIDISR_UVALID) && (max_count-- > 0));
        spin_unlock(&up->port.lock);
@@ -460,14 +463,11 @@ static unsigned int serial_txx9_get_mctr
 static void serial_txx9_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
        struct uart_txx9_port *up = (struct uart_txx9_port *)port;
-       unsigned long flags;
 
-       spin_lock_irqsave(&up->port.lock, flags);
        if (mctrl & TIOCM_RTS)
                sio_mask(up, TXX9_SIFLCR, TXX9_SIFLCR_RTSSC);
        else
                sio_set(up, TXX9_SIFLCR, TXX9_SIFLCR_RTSSC);
-       spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static void serial_txx9_break_ctl(struct uart_port *port, int break_state)
@@ -794,8 +794,13 @@ static void serial_txx9_config_port(stru
 static int
 serial_txx9_verify_port(struct uart_port *port, struct serial_struct *ser)
 {
-       if (ser->irq < 0 ||
-           ser->baud_base < 9600 || ser->type != PORT_TXX9)
+       unsigned long new_port = (unsigned long)ser->port +
+               ((unsigned long)ser->port_high << ((sizeof(long) - sizeof(int)) 
* 8));
+       if (ser->type != port->type ||
+           ser->irq != port->irq ||
+           ser->io_type != port->iotype ||
+           new_port != port->iobase ||
+           (unsigned long)ser->iomem_base != port->mapbase)
                return -EINVAL;
        return 0;
 }
@@ -837,7 +842,8 @@ static void __init serial_txx9_register_
 
                up->port.line = i;
                up->port.ops = &serial_txx9_pops;
-               uart_add_one_port(drv, &up->port);
+               if (up->port.iobase || up->port.mapbase)
+                       uart_add_one_port(drv, &up->port);
        }
 }
 
@@ -937,11 +943,6 @@ static int serial_txx9_console_setup(str
                return -ENODEV;
 
        /*
-        * Temporary fix.
-        */
-       spin_lock_init(&port->lock);
-
-       /*
         *      Disable UART interrupts, set DTR and RTS high
         *      and set speed.
         */
@@ -1051,11 +1052,10 @@ static int __devinit serial_txx9_registe
        down(&serial_txx9_sem);
        for (i = 0; i < UART_NR; i++) {
                uart = &serial_txx9_ports[i];
-               if (uart->port.type == PORT_UNKNOWN)
+               if (!(uart->port.iobase || uart->port.mapbase))
                        break;
        }
        if (i < UART_NR) {
-               uart_remove_one_port(&serial_txx9_reg, &uart->port);
                uart->port.iobase = port->iobase;
                uart->port.membase = port->membase;
                uart->port.irq      = port->irq;
@@ -1090,9 +1090,8 @@ static void __devexit serial_txx9_unregi
        uart->port.type = PORT_UNKNOWN;
        uart->port.iobase = 0;
        uart->port.mapbase = 0;
-       uart->port.membase = 0;
+       uart->port.membase = NULL;
        uart->port.dev = NULL;
-       uart_add_one_port(&serial_txx9_reg, &uart->port);
        up(&serial_txx9_sem);
 }
 
@@ -1195,7 +1194,7 @@ static int __init serial_txx9_init(void)
                serial_txx9_register_ports(&serial_txx9_reg);
 
 #ifdef ENABLE_SERIAL_TXX9_PCI
-               ret = pci_module_init(&serial_txx9_pci_driver);
+               ret = pci_register_driver(&serial_txx9_pci_driver);
 #endif
        }
        return ret;
@@ -1208,8 +1207,11 @@ static void __exit serial_txx9_exit(void
 #ifdef ENABLE_SERIAL_TXX9_PCI
        pci_unregister_driver(&serial_txx9_pci_driver);
 #endif
-       for (i = 0; i < UART_NR; i++)
-               uart_remove_one_port(&serial_txx9_reg, 
&serial_txx9_ports[i].port);
+       for (i = 0; i < UART_NR; i++) {
+               struct uart_txx9_port *up = &serial_txx9_ports[i];
+               if (up->port.iobase || up->port.mapbase)
+                       uart_remove_one_port(&serial_txx9_reg, &up->port);
+       }
 
        uart_unregister_driver(&serial_txx9_reg);
 }

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