linux-mips
[Top] [All Lists]

Re: [PATCH] serial driver PMC MSP71xx, kernel linux-mips.git master

To: Marc St-Jean <Marc_St-Jean@pmc-sierra.com>
Subject: Re: [PATCH] serial driver PMC MSP71xx, kernel linux-mips.git master
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Thu, 08 Feb 2007 15:13:09 +0300
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org
In-reply-to: <45CA5415.4000402@pmc-sierra.com>
Organization: MontaVista Software Inc.
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <45CA5415.4000402@pmc-sierra.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.7.2) Gecko/20040803
Hello.

Marc St-Jean wrote:
Fourth attempt at the serial driver patch for the PMC-Sierra MSP71xx device.

There are three different fixes:
1. Fix for DesignWare THRE errata
- Dropped our fix since the "8250-uart-backup-timer.patch" in the "mm"
tree also fixes it. This patch needs to be applied on top of "mm" patch.

2. Fix for Busy Detect on LCR write
- Changed the ordering of test in serial8250_interrupt().
- Combined test for UPIO_DWAPB with UPIO_MEM in serial8250_start_console().
- Renamed new uart_8250_port member to private_data.

3. Workaround for interrupt/data concurrency issue
- No changes since last patch.

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 3d91bfc..b309c4c 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -308,6 +308,7 @@ static unsigned int serial_in(struct uar
                return inb(up->port.iobase + 1);

        case UPIO_MEM:
+       case UPIO_DWAPB:
                return readb(up->port.membase + offset);

        case UPIO_MEM32:
@@ -333,6 +334,8 @@ #endif
  static void
  serial_out(struct uart_8250_port *up, int offset, int value)
  {
+       /* Save the offset before it's remapped */
+       int save_offset = offset;
        offset = map_8250_out_reg(up, offset) << up->port.regshift;

        switch (up->port.iotype) {
@@ -359,6 +362,18 @@ #endif
                        writeb(value, up->port.membase + offset);
                break;

+       case UPIO_DWAPB:
+               /* Save the LCR value so it can be re-written when a
+                * Busy Detect interrupt occurs. */
+               if (save_offset == UART_LCR)
+                       up->lcr = value;
+               writeb(value, up->port.membase + offset);
+               /* Read the IER to ensure any interrupt is cleared before
+                * returning from ISR. */
+               if ((save_offset == UART_TX || save_offset == UART_IER) && 
in_irq())
+                       value = serial_in(up, UART_IER);
+               break;
+               
        default:
                outb(value, up->port.iobase + offset);
        }
@@ -373,6 +388,7 @@ serial_out_sync(struct uart_8250_port *u
  #ifdef CONFIG_SERIAL_8250_AU1X00
        case UPIO_AU:
  #endif
+       case UPIO_DWAPB:
                serial_out(up, offset, value);
                (void)serial_in(up, UART_LCR); /* safe, no side-effects */
                break;
@@ -1383,6 +1399,19 @@ static irqreturn_t serial8250_interrupt(
                        handled = 1;

                        end = NULL;
+               } else if (up->port.iotype == UPIO_DWAPB &&
+                               (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {

Worth aligning this line with the opening paren of if... but's that's nitpicking. :-)

+                       /* The DesignWare APB UART has an Busy Detect (0x07)
+                        * interrupt meaning an LCR write attempt occured while 
the
+                        * UART was busy. The interrupt must be cleared by 
reading
+                        * the UART status register (USR) and the LCR 
re-written. */
+                       unsigned int status;
+                       status = *(volatile u32 *)up->port.private_data;
+                       serial_out(up, UART_LCR, up->lcr);
+
+                       handled = 1;
+
+                       end = NULL;
                } else if (end == NULL)
                        end = l;

        return 0;

   Still, shouldn't you be doing this in serial8250_timeout() also?
What IRQ numbers this UART is using, BTW?

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cf23813..bd9711a 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -276,6 +277,7 @@ #define UPF_USR_MASK                ((__force upf_t) (
        struct device           *dev;                   /* parent device */
        unsigned char           hub6;                   /* this should be in 
the 8250 driver */
        unsigned char           unused[3];
+       void                            *private_data;          /* generic 
platform data pointer */

   One tab to many before *private_data...

diff --git a/include/linux/serial_reg.h b/include/linux/serial_reg.h
index 3c8a6aa..1c5ed7d 100644
--- a/include/linux/serial_reg.h
+++ b/include/linux/serial_reg.h
@@ -38,6 +38,8 @@ #define UART_IIR_THRI         0x02 /* Transmitt
  #define UART_IIR_RDI          0x04 /* Receiver data interrupt */
  #define UART_IIR_RLSI         0x06 /* Receiver line status interrupt */

+#define UART_IIR_BUSY          0x07 /* DesignWare APB Busy Detect */
+
  #define UART_FCR      2       /* Out: FIFO Control Register */
  #define UART_FCR_ENABLE_FIFO  0x01 /* Enable the FIFO */
  #define UART_FCR_CLEAR_RCVR   0x02 /* Clear the RCVR FIFO */

   Oops, your mailer went and did it again. :-)

WBR, Sergei

<Prev in Thread] Current Thread [Next in Thread>